Articles

My Ninebark has a Foliar Disease. Help!

“I grow several varieties of ninebark, including the straight species native, and have not had any trouble the past 30 years. Last year for the first time some of the branches began to show what looked like powdery mildew, then shriveled and eventually turned black. This was very disfiguring on these wonderful shrubs and happened on all varieties. I cut them back severely over the winter and hoped it was last year’s summer weather (hot and dry) that brought on the disease. I showed leaves to a garden center, but they weren’t familiar. It’s just started back up on my shrub (been cool and wet). Do you know what it is and how to treat it? Thanks so much.” Question from D Shirer of Brecksville, Ohio

Answer: Ninebark is known to get powdery mildew, fireblight, and leaf spots, but none of the diseases are typically fatal to the shrubs. Based on my knowledge and research, it sounds like ninebark powdery mildew, and/or other mildew species, are the likely causes of your ninebark troubles. Mildew infections can appear earlier in the season, though they do tend to be most problematic in warmer, drier weather of summer, as you have observed.

Physocarpus and Powdery Mildew

According to an Amerinursery article titled Physocarpus and Powdery Mildew, three powdery mildew species can be responsible. In the article, the author writes, “The susceptibility of eastern ninebark to the specific ninebark powdery mildew (Podosphaera aphanis var. physocarpi) and generalist powdery mildews (Phyllactinia guttata and Podosphaera macularis) has been well-established.” He further writes, “Ninebark plants infected by powdery mildew commonly develop superficial patches of white fungal colonies on plant parts. In addition, the ninebark-specific fungus may produce bizarre witches’ brooms of thickened stem tissue with stunted foliage discolored white or light pink. These brooms turn black and further detract from the plant’s appearance by persisting through winter and beyond.” Do the symptoms and signs sound familiar? There are several steps you can take to stop mildew and other fungal diseases on your shrubs.

Steps to Controlling Powdery Mildew

I hope the information helps. Let me know if you have any other questions. If you would like to send photos. Please click here to learn how to reduce the size of your images for sending.

Happy gardening,

Jessie Keith

Black Gold Horticulturist

Glorious Hydrangeas for the Summer Garden

Blue lacecap hydrangeas are garden favorites, especially ‘Nachtigall’ (singer of the night). (Image by Mike Darcy)

The name Hydrangea denotes water and comes from the Greek words, hydor (water) and aggos (a jar). Together the words mean ‘water vessel’ because of the cup-like form Hydrangea seed capsules. I have looked at the seed capsule, and perhaps my imagination is not quite enough to describe them as water vessels, but hydrangeas do require regular soil moisture to look their best. Give them basic care, and they are some of the easiest summer-flowering shrubs you can grow.

As with many groups of plants, Hydrangeas are very diverse in flower color, leaf color texture, and growth habit. Their flowers can be different shapes and colors will vary from solid colors of white, pink, blue, purple, and cream to some that are bicolor in shades of pink and white. Leaf color is also variable and while most are solid green, some are variegated and some have burgundy foliage. They thrive throughout much of the Pacific Northwest and in many other parts of the country, except for areas with extreme summer heat or winter cold, and some species are not adapted to the deep South.

Hydrangea Selection

Tuff Stuff is a compact lacecap known to prosper in more difficult growing areas. (Image by Jessie Keith)

Selecting a hydrangea for the garden can be difficult because there are so many choices. It is difficult to only select one! Space is limited, and I cannot name all of my other favorites, but here is a selection of favorites from my garden.

Oakleaf Hydrangea

‘Snow Queen’ is my favorite oakleaf hydrangea. (Image by Mike Darcy)

If I had to pick just one hydrangea to grow, my choice would be Snow Queen oakleaf hydrangea (Hydrangea quercifolia ‘Snow Queen’). It is named because of the oak-like shape of the leaves and snowy summer flower clusters. This hydrangea is a sturdy grower with white upright panicles of single blooms that cover the plant in early to midsummer. It has deep green leaves all summer and in the fall, they turn a superb shade of red. Another plus is that oakleaf hydrangeas tend to take more sun than many other species.

Lacecap and Mophead Hydrangeas

‘Nachtigall’ has some of the best blue lacecaps. (Image by Mike Darcy)

Common bigleaf hydrangeas (Hydrangea macrophylla, USDA Hardiness Zones 6-11 (a few cultivars are bred to survive to Zone 5)) and mountain hydrangeas (Hydrangea serrata, Zones 5-9) have either mophead (with a puffy head of showy flowers) or lacecap (with a head showy flowers along the margins) blooms. Mopheads are more common, but I prefer lacecaps for their stately appearance. Their flowers are in shades of blue, pink, white, red, or purple. The blue/purple or pink/red types have flower colors that can change depending on the pH of the soil. Pinkish/reddish colors denote more alkaline soil, and purplish/blueish colors indicate more acidic soil.

One of the deepest blues of the lacecap types, and a spectacular specimen in my garden, is Hydrangea macrophylla ‘Nachtigall’ (5 feet x 5 feet). I first saw one in a garden last summer, and I kept walking back to it because it was such an impressive large shrub in full bloom. Some of the flowers looked as though they were almost double. Another I have had my eye on is a compact, pink-flowered lacecap called Tuff Stuff (3 feet x 3 feet) from Proven Winners. It is supposed to be exemplary and has a neat, rounded habit.

Three more favorite hydrangeas are known for both their foliage and flowers. They are the lacecap ‘Lemon Wave’, which has leaves with patches of white and yellow, the bigleaf lacecap called ‘Purple Leaf Form’, with its truly burgundy foliage, and a dark-purple-leaved mophead called Eclipse® with showy red and white flowers. All are striking in the garden and cause my visitors to comment.

Smooth Hydrangea

‘Annabelle’ is one of the prettiest smooth hydrangeas. (Image by Mike Darcy)

For large blooms, the native Annabelle smooth hydrangea (Hydrangea arborescens ‘Annabelle’, 3-8) is hard to beat. It is sometimes referred to as an old-fashioned snowball plant. The buds begin as pale white or light green and open to white. The blooms are very large, and the plant has a long blooming period in the summer.

Climbing Hydrangea

Schizophragma hydrangeoides ‘Moonlight’ is a lovely woody vine for shade. (Image by Mike Darcy)

While technically not a Hydrangea, climbing hydrangea (Schizophragma hydrangeoides ‘Moonlight’, Zones 5-8) is a close relative. The climbing lianna tolerates shade. In my garden, it only receives about an hour of morning sun and looks beautiful. Its heart-shaped leaves are almost silver and the lacy summer flowers are ivory.  Climbing hydrangea stems are stout and develop rootlets that attach to buildings, walls, or pergolas, so plant yours on a structure with strength and permanence.

Hydrangea Care

Hydrangeas like moist, not soggy, soil. Select a site that is protected from the hot afternoon sun. Morning sun or filtered sunlight is ideal. Water thoroughly, especially during the first year, and don’t let the soil become dry. At planting time, add a liberal amount of Black Gold® Natural & Organic Garden Compost Blend to the soil beforehand to increase organic matter. When planting hydrangeas in large pots, use Black Gold® All Purpose Potting Mix. Then add Black Gold® Perlite for increased drainage and aeration.

Eclipse® has both showy leaves and flowers. (Photography by Tracy Walsh, care of First Editions® Shrubs & Trees)

Hydrangeas species and varieties have different pruning needs. Some of the older cultivars bloom on second-year growth, and if heavily pruned in the fall, the plants will skip a year of bloom. Some bloom on new growth, so the time of pruning is not so critical. Those that bloom on new growth include the panicle hydrangea, which is not mentioned above (Hydrangea paniculata ‘Limelight’ is a good variety to try), and smooth hydrangea. Check the plant tag for pruning requirements. (Click here for more pruning guidelines from Proven Winners®.)

There are so many hydrangeas to choose from, and given the right planting conditions they can provide beauty in the garden for many years. A good rule of thumb as to how particular plants will perform in your garden is to talk with friends or neighbors who have them. If their plants are thriving, yours should, too. The month of May is an excellent time to plant. For more Hydrangea information, contact the American Hydrangea Society.

Why Are My Emerald Green Arborvitae Turning Brown on One Side?

“My Emerald Green arborvitae (Thuja occidentalis ‘Smaragd’) trees were planted by a professional landscaper along the outside of our screened-in porch in February 2019. In the first 3 years, they were lush and full. In the past 2 years, they have lost all of their needles in the side closest to the screen, have become spindly, and show no signs of new growth. What can we do to repair the damage? Have attached 3 photos. HELP!!! Thank you!” Question from George of Milton, Delaware

Answer: Emerald Green arborvitaes are tall, columnar, evergreen shrubs (15 feet by 3-5 feet) that require full sun (6 or more hours a day) on all sides to remain green all around. Sadly, yours have lost all foliage facing the shaded screen due to lack of light, while the sunnier side has maintained foliage. Moreover, based on the photo, it appears they may be competing for light beneath shade trees during part of the day, and the tall shrubs are planted too closely together too close to your porch. Lastly, their tall height prevents you from being about to see outside your porch, if you value your view.

Even with pruning and care, your trees will not develop healthy, green foliage on the shaded porch side, because there simply is not enough light. If the shrubs were moved, they may have a chance, though they are quite large. You might consider replanting shorter evergreens tolerant of shade. I am familiar with Milton, Delaware, and the area around Lewes and Rehoboth.  I recommend planting an attractive shrub tolerant of lower light and the sandy, coastal-plain soils of Sussex County. I’ll recommend some good evergreen and non-evergreen shrub options.

Shrub Recommendations

Look for evergreens tolerant of shade, like tough rhododendrons.

Inkberry (Ilex glabra cultivars). The native shrubby evergreen is tolerant of partial shade, unlike most evergreen hollies. There are many quality varieties available for sale. According to an extensive study at Longwood Gardens, ‘Densa‘ was the best-performing variety trialed. It reaches a mature height of 4-7 feet and is easily pruned. The 5-foot ‘Shamrock‘ is another notable variety to look for, and Proven Winners has introduced several other good inkberries. Give them plenty of water, especially as they are becoming established in the first year.

Azaleas or Rhododendrons may be evergreen or deciduous and quite a few grow beautifully in the area. the evergreen PJM Hybrid Rhododendron (4-6 feet at maturity, Zones 4-7) is a good option with an attractive, rounded habit, lavender-pink flowers that bloom in mid-spring, and evergreen foliage (dark green in summer and reddish in winter). It is tough, reliable, and tolerant of shade.

Hydrangeas provide a good deciduous option with summer flowers. I favor dwarf varieties of oakleaf hydrangea (Hydrangea quercifolia), like Ruby Slippers, or a smooth hydrangea (Hydrangea arborescens) like the tough, 5′ x 5′ Lime Ricky.

Contact the Delaware Center for Horticulture for more good shrub ideas.

Before planting any new shrubs, consider amending your soil with organic matter to fill in the sandy pore spaces and hold water and nutrients. Black Gold® Natural & Organic Garden Compost Blend or peat moss are good, organic options.

Happy gardening,

Jessie Keith

Black Gold Horticulturist

From this angle, it appears there are shade trees quite close to your porch further shading your arborvitae.

What Is The Best Potting Mix for Potted Shrubs?

“I will be planting shrubs in containers. Which potting mix between Fafard and Black Gold would be the best choice and longest lasting? I would prefer something more permanent so as to not have to change out the potting mix every few years. I live in zone 7. Thank you for your response.” Question from Mel of Atlanta, Georgia

Answer: When recommending the best soil for potted shrubs that will be there for the long term, I always suggest filling the pots with 1/3 quality topsoil or ground soil and 2/3 quality potting mix. Mix the two evenly before filling the pots. I like to add ground soil because potting mixes tend to acidify over time, and ground soil, which is primarily inorganic, helps buffer the acidification process, and it will not break down and shrink over time. You might also consider adding some other ingredients, such as sand or pebble, depending on the shrubs grown. Finally, be sure to refresh the pot with new potting mix seasonally. The addition of dolomitic lime can also reduce acidification.

With that said, I would choose the following mixes for long-term potted shrubs.

Feed your shrubs seasonally in the spring with a slow-release fertilizer. It is also important to note that potted shrubs are most apt to survive winter if they are at least two zones hardier than your zone because they are more exposed.

All the best,

Jessie Keith

Black Gold Horticulturist

Forever Jolly Winter Hollies

Sparkleberry winterberry forms a cloud of tiny red berries in December, and birds love them. (Image by Jessie Keith)

Berried holly branches are a ubiquitous holiday symbol, but these festive trees and shrubs come in more colors than just red and green, and many offer landscape interest beyond the winter season.  My favorite winter hollies (Ilex spp.) are forever beautiful, whether berried at the end of the season or clothed in new spring foliage. Here are five that continuously shine in the garden, offering year-round splendor and high landscape utility.

There is only one essential bit of information to know when growing any holly. The shrubs are dioecious, meaning that each shrub is either male or female. Only the females produce colorful berries, while at least one male is needed to provide pollen to the females for a successful fruit set. So, plan to plant at least one complementary, pollenizing male for female berry producers, and make sure that the male is a compatible variety.

Beautiful Winter Hollies

Variegated English holly is one of the prettiest hollies for gardens.

Variegated English HollyIlex aquifolium ‘Argentea Marginata’

(USDA Hardiness Zone: 7-9; Height: 12-24 feet)

Crisp white edges keep the variegated foliage of this classic English holly tree looking lovely all season. In spring, the shrubs are beautifully complimented by landscape bulbs, such as bright tulips and alliums, and in summer colorful annuals provide an equally complementary color boost. In late summer and fall, green berries turn to red and remain beautiful well into winter. The tree to large shrub develops a conical habit over time. Plant in full sun and provide slightly acid, well-drained soil for best growth. The equally variegated ‘Gold Coast‘ is the perfect male pollenizer for this variety.

 

Ilex crenata 'Drops of Gold' PP14420 JaKMPMGolden Japanese HollyIlex crenata ‘Drops of Gold’

(USDA Hardiness Zone: 5-9; Height x Width: 5-7 feet x 10-12 feet)

Truly golden boxwood-like foliage is the hallmark of this favorite Japanese holly. The golden outer foliage looks great all season and is complemented by red-, orange- and purple-flowered ornamentals in spring, summer and fall. Black berries develop on the shrubs in fall, but these offer little visual interest. The more sun this holly is given, the more golden and full the foliage becomes. Don’t be deceived by its compact size at purchase; ‘Drops of Gold’ grows to be quite large and broad over time.

 

Sky PencilJapanese HollyIlex crenata ‘Sky Pencil’

(USDA Hardiness Zone: 6-9; Height x Width: 4-10 feet x 1-3 feet)

Few shrubs reach up to the sky as well as the uniformly upright ‘Sky Pencil’. The popular evergreen shrub is revered for its architecturally clean verticality, and it looks super all year long. The all-male variety bears no fruit, but its fine, glossy, rich green foliage never stops looking good as long as plants are provided full sun and slightly acid soil with average to good drainage. This is a shrub that does not appreciate high wind, so plant it in a somewhat protected location.

 

066Variegated WinterberryIlex verticillata ‘Sunsplash’

(USDA Hardiness Zone: 4-8; Height x Width: 4-7 feet x 3-5 feet)

The unique winterberry ‘Sunsplash’ bears lots of red berries on deciduous stems in fall and winter, but it also has the added bonus of gold and green variegated foliage that looks especially pretty in spring and early summer. The variegation is not uniform, but it has landscape appeal. This Broken Arrow Nursery introduction makes a unique addition to the landscape, and like all winterberries, it will grow well in the moister ground than most other hollies. Specimens planted in higher light will have the lightest variegation. If you are not keen on variegation, try the compact ‘Sparkleberry‘, which produces many small, bright red berries. Plant them with the male counterpart, Apollo‘.

 

Dwarf Japanese HollyDwarf Yaupon HollyIlex vomitoria ‘Stokes Dwarf’

(USDA Hardiness Zone: 1-11; Height x Width: 2- 3 feet x 4 feet)

This little bitty evergreen holly looks so pretty in small garden spaces. The shearable, slow-growing shrub develops a low, mounding habit and boasts deep green foliage that never stops looking nice. Like all yaupon hollies, ‘Stokes Dwarf’ is fairly tender and best planted where winters are relatively mild. Plant this one as you would any dwarf boxwood. Sharply drained soil and full sun are necessary for good growth and appearance.

Caring for hollies is not rocket science. Full to partial sun keep their foliage full and growth uniform and attractive. Sufficiently drained soils that are slightly acid are best. Amendment and mulching with Black Gold Garden Compost Blend in mid- to late-fall is recommended as is light fertilization with an all-purpose fertilizer in spring. Please click here for planting details by plant expert, Russell Stafford.

Whether large, small, bushy, or tall, every one of these holly shrubs is glorious in the landscape and garden. So this year make all seasons holly seasons. Plan to plant one of these forever jolly hollies in your spring garden.

How to Prune Spring-Flowering Shrubs

Unless you are removing dead or dying stems, it is best to prune spring-flowering shrubs just after they bloom.

When we think of pruning shrubs, we probably think of late fall and early winter as the ideal time, but this is not always the case. For many spring-flowering shrubs, late spring is the best time to prune because pruning must happen shortly after flowering. Prune off-season, in fall or spring, and you will remove the following year’s flower show! In my own garden, I have many spring-flowering shrubs that need late spring or early summer pruning, so I have learned to time my pruning carefully.

As a rule, most spring-flowering shrubs must be pruned just after or shortly after flowering because this is the time when they set new buds for next spring’s show. Prune them later in summer, and you will end up trimming off next year’s flower buds. For this reason, I have highlighted just a few spring-flowering shrubs and tips for pruning them.

My favorite pruning tools are simple. For large stems, I use a sharp pruning saw or heavy-duty loppers. Bypass pruners (secateurs) are used to manage smaller branches or for deadheading.

Pruning English or Cherry Laurel

The spring flowers of evergreen cherry laurel shrubs are very showy and fragrant, which is why it is important to prune them at the right time.

The plant that immediately comes to my mind that requires at least two prunings a year is the English Laurel, (Prunus laurocerasus, USDA Hardiness Zones 6-8, 10-18 feet), a hedge that my neighbors have. It is an evergreen and fast-growing shrub with dark glossy green leaves and has spikes of creamy white fragrant flowers in late spring. The scent is sweet and powerful, and the shrubs look very attractive in bloom.

My neighbors always give it a heavy pruning after it blooms and then another pruning later in the summer. They also selectively prune to keep the favorite hedge shrubs open and airy, which helps prevent disease problems. Theirs is certainly a taller variety that would take over the house without being pruned twice yearly.

Pruning Azaleas and Rhododendrons

Most often gardeners prune off old azalea and rhododendron blooms after they flower in addition to removing the occasional errant branch.

Rhododendrons and azaleas (Rhododendron species and hybrids, variable hardiness and sizes) will both bloom on second-year wood, so they benefit from spring pruning just after they have flowered. Any later and you risk accidentally removing next year’s blooms. Often the process for both is referred to as ‘deadheading’ because the old flower is removed.  Once the flower has faded, it can be removed. Not only does this look nicer, but it allows the plant can expend energy for new growth instead of seed production.

Deadheading a large rhododendron plant can be quite time-consuming, but it is well worth the time. The plant will physically look better without faded flowers and it saves the plant energy. Some care is required when removing the old blooms. If you look carefully, each has a tender stem that can be snapped off just below the bloom. This is where care is required because it is important to just remove everything above the stem–nothing below because all of the new growth will emerge below the stem.

Generally, rhododendrons and azaleas do not require more intensive pruning unless it is needed for space considerations or plant shaping. If pruning is required, do it immediately after flowering so the plant has adequate time to produce new growth for next year’s flowers.

Pruning Lilacs

The common lilac (Syringa vulgaris, Zones 3-8, 8-20 feet) is another plant that usually requires spring pruning. Once the plant has bloomed, cut off the spent blossoms. To do this, make the cuts back to the first or second pair of leaves on the stem.

If the shrub needs some major pruning, do it immediately after flowering because these lilacs bloom on wood from the previous year. On established plants, cut out a few of the oldest stems yearly and this will encourage new growth. It is also important to remove dead or dying stems, as needed, to keep the shrubs looking their best.

Pruning Tree Peonies

Tree peonies rarely need extensive pruning, but a little yearly deadheading and shaping will keep them performing their best.

The tree peonies (Paeonia suffruticosa, Zones 4-8, 3-5 feet) in my garden have finished their flowering season, so it is time to cut off the old flowers to keep the plant from producing seed. I do this with hesitation because the brown, starry seedpods open to show bright red or black seeds, which can be quite attractive. But, the seeds also take needed energy away from the plant. To have the best of both worlds, I sometimes leave some pods on to look nice. In general, shrubby tree peonies do not need to be pruned extensively, unless it is to remove a stray or dead branch. These architectural slow growers are usually happy just remaining as they are.

Pruning Camellias

My Japanese camellias (Camellia japonica, Zones 7-9, 7-12 feet) put on their greatest show in late winter or spring, but they will also bloom intermittently. Generally do not need pruning except to improve the appearance of the plant or for space considerations. I also remove the old flowers after they are spent to keep the shrubs looking nice and clean. When I do decide to prune, I do it immediately after flowering.

I have found that most spring-flowering shrubs are fairly forgiving with regard to pruning if you are sure to prune them after they flower and no later. If mistakes are made, the plant will survive. Severe pruning may eliminate, or decrease flowering for the next year, but the plant will carry on. Remember that gardening should be enjoyable, so don’t stress too much about potential pruning mistakes. Common sense is a good trait!

Does Mulch Along a Home’s Foundation Attract Termites?

Does Mulch Along a Home’s Foundation Attract Termites?

“I’ve heard that its not a good idea to place mulch too close to a house’s foundation. I was also told to mulch or plant shrubs around my house’s foundation to prevent my kids from getting lead poisoning from the old chipped off paint in the soil. What should I put near my foundation, bricks? Also, how far from my foundation should I plant vetiver grass? I’m having trouble finding guidance on how far from my brick foundation it should be with its deep root system.” Veronica of Clay City, Indiana

Answer: Some speculate that termites may be attracted to or reside in bark mulch. It is true that termites can eat bark mulch, but they survive and form colonies in solid wood, so bark mulch not a terribly strong termite lure. Moreover, newer homes are generally protected from termites, and older homes should be for their longterm protection.

Either way, there are other mulch options that are certain not to harbor or attract any termites. These include pine straw, chopped leaf mulch, stone mulch, and even quality Black Gold Garden Compost Blend. (Please click here for a full overview of different mulch options.) My personal favorite is pine straw. It looks tidy and really helps to detur weeds.

The best way to keep kids away from the soil at the base of the home is to plant lawn or shrubs along your foundation (click here for some good flowering shrubs for foundations). Ornamental grasses are another option, but I would not recommend vetiver grass (Vetiveria zizanoide, Zones 7-8) because it is a warm-climate grass that will not be hardy in your Zone 5 garden, and it is weedy. Better, more beautiful, sun-loving grasses for your foundation include Karl Foerster Feather Reed Grass, Prairie Winds® ‘Apache Rose’ Switch Grass, or Little Zebra Dwarf Zebra Grass. All need sunshine and should be planted 2 to 4 feet from your foundation in a mulched bed, depending on the final height and width of the grass you choose.

I hope that these tips help!

Happy gardening,

Jessie Keith

Black Gold Horticulturist

Viburnums For Any Landscape

Right: bright red Viburnum opulus berries, do droop. They also feed hungry songbirds.

What exactly is a Viburnum? Viburnums are trees or shrubs, evergreen or deciduous, that may be diminutive three-foot globes or grow 60 feet tall. Their leaf texture varies from smoothly shiny to velvety, and, their leaf edges may be serrated, dentate, lobed, or not! Viburnum flowers are either round or flattish and range in color from white to pink. The blossoms are either deliciously fragrant, have absolutely no scent, or can be downright offensive. Just forget trying to determine what viburnum you are admiring by its fruit color alone since berries range from yellow to orange, red to black, and blue to purple.

According to the great Georgia plantsman, Dr. Michael Dirr, their characteristics are simply too varied to make a definitive identification without a very good reference guide. In his 2007 guidebook, Viburnums, Flowering Shrubs for Every Season, by Timber Press, Dirr admits that even taxonomists can’t agree on how many species presently exist in the genus Viburnum with the true number probably falling somewhere between 160 to 250.

What makes a Viburnum a Viburnum?

V. Carlesii - Photo by Pam Beck
The Koreanspice bush, V. carlesii, provides a perfect example of a viburnum’s opposite leave arrangement.

Famed tree and shrub specialist Michael Dirr’s definition is:

  1. The fruit is a drupe, generally ellipsoidal, flattened, ovoid to rounded, with a fleshy coat, hard bony endocarp, and a single seed within; and
  2. The leaves are always arranged opposite; a few species, occasionally, have three leaves at a node.

Growing Viburnum

Viburnum diltatum (Image by KENPEI)

Besides their exquisite beauty, the main reason why we embrace viburnums in our home landscapes is their extreme hardiness. Many varieties can be very drought tolerant (once established) as some of our best Southeastern native viburnum hail from dry woodlands. A few, such as our native Arrowwood, will also tolerate wet feet. Most will grow well in full sun to part shade, can take a variety of soil types, and still thrive.

Planting Viburnum

In the absence of good soil, you could amend the planting hole fill dirt with Black Gold Garden Soil for improved drainage that will still provide enough moisture retention essential for a newly transplanted viburnum. Otherwise, mulch the base of your new addition with Black Gold’s Garden Compost Blend in order to help hold moisture, keep developing roots cool in summer and warmer in winter, and to suppress weeds.

Great Viburnum

In my home landscape, I have found several species of viburnum grow well under the canopy of a large Black Walnut tree, where it is very dry. Here I have planted Koreanspice bush (V. carlesii) and Cranberry viburnum (V. opulus), and they both perform beautifully.

Viburnums have also been evaluated for their resistance to deer grazing. The toughest survivors of deer predation are our native Arrowwood (V. dentatum); Blackhaw (V. prunifolium); Smooth witherod (V. nudum), which is sometimes erroneously called “possum haw” and, the Maple-leaf arrowwood (V. acerfolium).

Koreanspice Viburnum

The flowers of Koreanspice viburnum are so fragrant. (Image by Bouba)

Koreanspice viburnum (V. carlesii, Zones 4-7) is one of our most popular, old-fashioned, pass-along southern shrubs. Grown for its intensely sweet springtime fragrance, the late March to early April flowers of Koreanspice begin pale pink, turning white with age, grow 2-3 inches across, and are rounded. This 8-10 foot tall shrub has dull green leaves that turn reddish in the fall, and red to black fruits.

Cranberry Viburnum

Cranberry viburnum is named for its brilliant cherry-red fruit clusters that begin coloring in late summer. The popular double-flowered variety ‘Roseum’ is sterile and bears no fruit.

The Cranberry viburnum is named for its brilliant cherry-red fruit clusters that begin coloring in late summer. Its famous leaf fall color is much more dramatic in cooler regions where leaves turn gold, red, and burgundy. A very good cultivar is V. opulus ‘Compactum’, which should top out at just 5-6 feet.

Chinese Snowball

For sheer drama, nothing compares to the Chinese Snowball (V. macrocephalum). This multi-trunked small tree can reach 12-feet or more in height and grow just as wide. Sometimes semi-evergreen in mild winters, this very dark-leafed viburnum is beloved for its 6-8 inch, rounded, springtime flowers that begin pale chartreuse and age to purest white. They are so beautiful that we can forgive it for not bearing any scent. A significant bonus is that it also flowers again from late summer into fall. Since the Chinese Snowball’s hydrangea-like flowers are sterile, there is no fruit, therefore no unwanted seedlings.

Bodnant Viburnum

Viburnum x bodnantense ‘Dawn’ is an early bloomer with lovely fragrant pink flowers. (Image by Magnus Manske)

Your winter landscape could be delightful including a Bodnant viburnum in it. Viburnum x bodnantense ‘Dawn’ has bright pink, strongly perfumed flowers in late February to early March in my Wake Forest, North Carolina, Zone 7-8 garden. The small, rounded, sweetly fragrant flowers are borne on bare branches on a rather rangy shrub, but ‘Dawn’ blends nicely into the mixed border the rest of the year.

Viburnum Tinus

Garden centers offer V. tinus ‘Spring Bouquet’ in autumn, which is the right time to plant them. During the late fall months ‘Spring Bouquet’ forms tight rose-colored clusters of buds that will start popping open during the first months of the new year. These viburnum flowers are only slightly fragrant, but they will cover the small shrub. This evergreen viburnum will need part shade in summer, winter protection from sun, plus they benefit from being shielded from desiccating winds.

Doublefile Viburnum

Doublefile viburnum (Viburnum plicatum) has lovely tiered branching and should not be pruned.

Since they bloom in early April, Doublefile viburnums, V. plicatum f. tomentosum, are great substitutes for ailing native dogwoods. Named for its flowering habit of doily-flat flowers positioned side-by-side along the top of long horizontal branches, this is a stunning small tree. These viburnum are deciduous in winter, have dark green foliage in summer, and bright red berries in late fall. A cultivar named ‘Summer Snowflake’ will bloom well in early spring, then sporadically repeat off-and-on throughout the summer.

Chindo Viburnum

Chindo viburnum is another popular viburnum that isn’t grown for its flowers at all. Promoted by the late Dr. J C Raulston of North Carolina State University, V. awabuki ‘Chindo’, is a loosely pyramidal-shaped, shiny-leafed, evergreen shrub that can reach 15-20 feet. It grows in sun or shade and is shaped reminiscent of a large-leafed holly, so it makes an ideal screening plant. One warning is that a Chindo viburnum won’t like winter temperatures that drop below zero; so, if it does get that cold you may have to trim your plant back severely in springtime to encourage new growth to flush.

There is probably a perfect viburnum for just about any location in your landscape, so how do you go about narrowing your selections? Ask your garden center professional for their recommendations, check with your local Cooperative Extension Service, and find a copy of Dirr’s Viburnums book.

 

V. awabuki ‘Chindo’ - Photo by Pam Beck
The ‘Chindo’ viburnum is an outstanding evergreen screening shrub. (Photo by Pam Beck)

What Are Good Shrubs for a Home’s North Side?

Gold-and-flame-leaved Forest Flame reaches 6 to 10 feet and has chains of ivory spring flowers.

“I am having trouble with roses in the constant north side shade area of my home. Looking for a possible flowering shrub or a better suggestion for this area at the front of our house.” Question from Larry of O’Fallon, Missouri

Answer: Roses by default are sun-loving. Just a handful of species roses and cultivated roses will tolerate partial shade. (Click here to read another AGE about shade-tolerant roses.) But, there are loads of flowering shade-tolerant shrubs that will grow beautifully on the north side of a home. Here are some of my favorites. All of them should be hardy where you live in Missouri.

Shade-Loving Shrubs

Reblooming Azaleas (Rhododendron spp.): Encore® and Bloom-A-Thon® Azaleas will rebloom and some are even evergreen. I recommend them if you have slightly acid to acid soils with good drainage.

Smooth Hydrangea varieties (Hydrangea arborescens): Tolerant of sun and shade, smooth hydrangeas are very hardy and native to your region. Some of the new varieties bloom for a long time in summer, and then their flowers remain on the plants and continue to look pretty into fall and winter. I love the many varieties sold by Proven Winners, such as the pink-flowered Invincibelle, among others. (Click here to view them all.)

Yak Rhododendrons (Rhododendron hybrids): There are so many outstanding evergreen Rhododendrons that grow beautifully in shade, and yak forms are extra tidy and compact. ‘Grumpy‘ is an outstanding yellow-and-pink-flowered form that reaches 5 feet at maturity and has dark, evergreen leaves.

Lily of the Valley Shrub (Pieris japonica) is another evergreen that likes growing conditions similar to that of azaleas and rhododendrons. Interstella has pink chains of blooms in spring and only reaches 4 feet at maturity. Larger varieties include the outstanding gold-and-flame-leaved Forest Flame, which reaches 6 to 10 feet and has chains of ivory spring flowers. It’s a real showstopper.

Hartlage Wine sweetshrub (Calycanthus x raulstonii ‘Hartlage Wine’) grows well in partial sun to light shade and has very fragrant maroon-red flowers in late spring. At maturity, it reaches 6 to 8 feet, so give this one some space. In autumn, its leaves turn yellow and orange before falling.

We have an excellent article, by horticulturist Russell Stafford, that details how to properly plant new shrubs in the landscape. Please click here to view it. I hope that some of these shrubs interest you!

Happy gardening,

Jessie Keith

Black Gold Horticulturist

How to Plant and Site Trees and Shrubs

The key to successful gardening is to go (and grow) with what you’ve got. If your garden has acid soil and lots of shade, go with acid- and shade-loving plants. If sunny, dry, alkaline conditions dominate, then plan and plant accordingly. This also holds true for the garden’s aesthetic. For example, more “naturalistic” settings (such as a woodland edge) call for more informal, nature-evoking plantings. Beautiful and bountiful things happen when a garden is in harmony with its surroundings.

Understand Your Garden’s Site

Light, soil, space, garden style, and other parameters must be considered before planting a new tree or shrub.

It’s especially important to keep this in mind when choosing – and planting – the trees and shrubs that will form the framework of your garden.  Choose the right plants and get them off to a good start, and good things are almost sure to follow.

It all comes back to knowing the site’s conditions. What are the pH, nutrient-holding capacity, and other characteristics of your soil? If in doubt, you can get a definitive answer by sending soil samples to your state’s horticultural extension service (click here for a nationwide list of extension services). What is the site’s exposure to sun, wind, and water (e.g., rain and runoff)? How and when do you use your yard? Now, during the dormant season, it is a great time to assess these factors. Then, based on your site’s particulars and your preferences, compile lists of trees and shrubs that are a good fit.

Planting Trees and Shrubs

A suitably broad planting hole should be around three times as wide as the plant’s root ball.

When you get around to planting, the same precepts remain. Trying to force an ill-chosen plant into an incompatible site is a losing prospect. If the tree or shrub is a good fit, all it needs is a good root system and a suitably broad planting hole, backfilled (to the proper depth) with unamended or lightly amended soil for best establishment. Of course, planting at the proper season and providing regular post-planting care (especially watering) are also essential.

Sizing Up the Planting Hole

Adding a light application of soil amendment, such as Fafard Premium Topsoil, will give the soil extra organic matter.

Planting width requires a “suitably broad” planting hole is at least three times as wide as the plant’s root ball, although twice as wide will do in a pinch. The texture of the excavated and refilled soil differs significantly from that of the surrounding undisturbed soil; consequently, it also differs significantly in other properties such as moistness and aeration. Adding a light application of soil amendments, such as OMRI Listed Black Gold Canadian Sphagnum Peat Moss or Black Gold Garden Compost Blend, will give the soil additional organic matter for increased water-holding ability to help the establishing plant. This is of greatest importance in poor or sandy soils. If your soil is of good to average quality, this step is not needed. A wide planting hole gives the roots a relatively homogeneous environment in which to extend and establish. By the time they’ve reached the edge of the former planting hole, they’ll be more up to the job of worming their way into the undisturbed soil. Additionally, the refilled soil will settle over time to a texture closer to that of the surrounding soil, thereby easing the roots’ transition.

The planting hole should be no deeper than the root ball.

Planting depth – unlike width – can be overdone. In fact, the planting hole should be no deeper than the root ball. Most of a tree’s or shrub’s feeder roots are within a few inches of the surface. A deeper hole serves only to loosen the texture of the soil below the root ball, increasing the likelihood that it will settle and pull the roots down with it. Plants generally do not thrive in air-starved sinkholes.

Work soil in around the plant and press it down to remove any unwanted air pockets.

Shallower planting may be required in heavy clay soil. Planting holes in such soils are subject to the bathtub effect, with water percolating through the relatively coarse refill soil and pooling at the bottom of the hole. Here, dig an extra-wide hole that’s significantly shallower than the root ball, sloping the base of the hole toward its edges. Mix the excess backfill with Black Gold® Garden Soil, and mound this over the exposed root ball after planting.

Sizing Up the Tree or Shrub

Make sure plant roots have not become pot-bound. If they have, work them apart to help them grow into the soil.

Potted trees and shrubs with vigorous, relatively undisturbed roots make the best planting material. Avoid pot-bound plants whose roots have long ago filled or grown beyond their containers. Before buying a containerized plant, try to knock it out of the container to check the root system. If the root ball remains stubbornly wedged in its container even when you apply force to remove it, it’s a risky prospect. Ideally, the roots should not circle the soil ball, and abundant white feeder roots should be evident at its edge. You can plant container-grown trees and shrubs just about any time the ground is workable, but be sure to keep the root ball from drying out after planting. Most potting soils are peat-moss-based, making them coarser and more drought-sensitive than the surrounding soil. They also resist re-moistening once completely dry. Newly planted container-grown plants may need watering several times a week during summer droughts.

Unlike container-grown plants, B&B plants are often grown in heavy clay, which cracks and resists water when dry.

Bare-root and balled-and-burlapped (B&B) trees and shrubs lose much of their root systems when harvested at the nursery. They thus require more kid-glove treatment. Plant them either in early spring or in late summer/early fall to give their roots ample time to regrow before summer heat or winter cold arrives. Be sure that their roots do not dry out before planting. Unlike container-grown plants, B&B plants are often grown in heavy clay, which cracks and resists water when dry.

Be careful to plant bare-root and B&B shrubs and trees at the proper depth. For bare-root plants, partially refill the planting hole with a volcano-shaped cone of soil, spreading the roots atop the cone before backfilling. The plant’s trunk/root junction (also known as the “root flare”) should be just at or slightly above the soil surface. Stems of B&B trees and shrubs are often partly buried in their root ball; if so, remove some of the soil to expose the root flare. Also, be sure to minimize disturbance to B&B root balls as you plant, and remember to unswaddle the burlap (or wire caging) from the top and sides of the root ball before refilling the hole. Either cut and discard the unwanted wrap or pull it back and bury it at the bottom of the hole.

A two- to three-inch mulch layer will hold in soil moisture and protect against weeds.

Add a good mulch layer to buffer newly planted trees and shrubs from drought, heat, and cold, and apply an inch of Black Gold® Natural & Organic Garden Compost Blend and a couple of inches of bark mulch to the planting area. They’ll appreciate the extra pampering, and you’ll appreciate the results!