“When is the best time to fertilize Rhododendrons?” Question from Carin of Fall Creek, Wisconsin
Answer: When it comes to questions about Rhododendrons and Azaleas, even experts like me turn to the American Rhododendron Society. Their goal is to teach gardeners how to make the most of these beautiful flowering shrubs. Their advice follows that of professional growers: if the plants look happy, perform well, and have fertile, well-drained soil that is slightly acid, then there is no need to feed them. Excess fertilizer can actually damage their roots. But, if your soil is sandy and poor, then I recommend amending it with Black Gold Peat Moss and Garden Compost Blend to increase water- and nutrient-holding ability. From there fertilize in the early spring with a food formulated for acid-loving plants, like rhododendrons. (Click here to read more.)
“I have many azalea bushes in my yard, and this year, I had three suddenly die off. I couldn’t detect any pests or that type of issue. They were around a tree, and all four lost their leaves very quickly. One has sprouted green. One seems quite dead, and the other two are still bendable and not dead, but have no leaves. Any thoughts on what caused this? Also, do you feel the others that are bendable may come back?” Question from Mary of Longwood, Florida
Answer: There are several fungal diseases that can cause stem dieback and/or sudden death in azaleas. All become more pronounced when there is excess moisture, humidity, and the soil is not sharply drained. Here are the top three possibilities.
Azaleas Diseases that Cause Sudden Death
Phytophthora Root Rot (Phytophthora cinnamomi) is a common, fast-acting, deadly disease of azaleas, and excess soil moisture and warmth encourage its growth and spread. Some infected plants will wilt and die very quickly. Others will grow slowly and may have poor-looking living branches, but infected plants typically succumb to death pretty quickly. To identify this disease, look for discolored, reddish-brown roots that are dead or dying. Badly infected plants will show the same discoloration on the lower stems. Remove all infected shrubs and dispose of them away from your garden. Sadly, this disease remains in the soil, so consider raising the soil in your beds to encourage better drainage, and plant something different in the spots. (Click here for good information about the best Florida landscape plants.)
Phytophthora Dieback (Phytophthora cactorum) is the most common azalea disease that causes dieback. It is also a disease caused by poor soil drainage. The first symptom is wilting with leaves that curve inward. One difference from root rot is that the roots look blackened and pull up easily. The stem will often show brown discoloration at the base near the soil surface. Treat as you would for Phytophthora root rot.
Rhizoctonia Root Rot (Rhizoctonia solani) is a deadly disease that behaves like the others, but the plants exhibit severe brown and black spots on the leaves, so I don’t think that this is the disease that took your azaleas.
When removing any diseased plant material, rake away and remove any dead leaf or stem material that may be contaminated with disease-causing spores. When pruning your surviving azaleas, avoid cross-contamination by cleaning your pruners in a 10% bleach solution when making cuts from one plant to another. Adding additional topsoil and amending beds and new planting areas with fertile organics, like Black Gold Canadian Sphagnum Peat Moss, will help any future azaleas that you plant.
Azaleas properly planted in well-drained soil need regular water. One other less likely option is that your shrubs dried up due to lack of water. If this could be the cause, I suggest laying drip hose around the remaining azaleas, applying mulch, and irrigating the shrubs once or twice weekly in the absence of drenching rain.
“This is my favorite time of year”, is a phrase that I seem to use for every season because every season is my favorite time of year. However, after a relatively mild winter and with spring here, gardens all over are bursting with color and new growth. Probably because we did not have a late frost to damage the emerging flower buds, the deciduous magnolias have been magnificent. I cannot remember a year when I have seen them display such a show of color. A particular favorite in my garden is Magnolia ‘Black Tulip’ as the flowers are a very deep purple and the buds do resemble the flower of a tulip.
Not to be outdone by the magnolias, camellias have also been putting on a great show. Driving around older neighborhoods in Portland, camellias were very often used as a foundation plant. There was a period of time when they seemed to be out of favor, but recently they are making comeback and gardeners are rediscovering them. Our climate seems ideal for them and with some amendments to the soil, they will thrive. Camellias like a soil rich in organic matter and Black Gold Garden Compost Blend is a perfect addition to add to the soil at time of planting.
Not only are gardeners rediscovering camellias, but they are also learning that they come in a wide array of flower types and colors. Camellia flowers come in shades of red, pink, and white with many varieties displaying two on more colors in the same flower. The flowers themselves come in single, double, semi-double, peony shape and the list goes on. Different camellia plants will often bloom at different times of the year and by taking advantage of this, gardeners canhave camellias in bloom from December through May. A popular Camellia, ‘Yuletide’, blooms at the holiday season, as the name implies. I have seen many homes with a container of ‘Yuletide’ at an entryway during the Christmas season with the plant in full bloom. Camellias can easily be grown in containers filled with rich potting soil, and Black Gold All Purpose Potting Soil is excellent.
The Pacific Northwest is known for growing rhododendrons and many of the early-flowering types are in bloom before the end of March. Similar to camellias, the bloom period can be extended from early spring to early summer when choosing different varieties. The planting conditions for rhododendrons are also similar to camellias and the addition of Black Gold Garden Compost is an ideal additive.
Of all the rhododendrons that I see, my favorite continues to be Rhododendron yakushimanum ‘Yaku Angel’. I have had one of these in my garden for many years and even when the plant is not in bloom, it is a beautiful shrub. The leaves have a brown indumentum (velvet-like material on the underside of the leaves) that is very soft to the touch. In early April, the flower buds emerge pink and as the open, they turn white. This is a stunning sight to see, as the bush is covered with pink flower buds and pure white flowers. If I had to pick one rhododendron, this would be it.
Magnolias, camellias, rhododendrons, this is just the beginning of what blooms in April in our Pacific Northwest Gardens. Soon it will be peonies, then lilies, then dahlias, and the summer perennials and annuals. Remember that when planting permanent plants that thrive in a soil rich in compost, your opportunity to do this is when you are planting. Make your soil environment the best you can to suit the needs of the plants you are planting.
In the summer of 2015, the Pacific Northwest experienced one of the longest periods of no measurable rainfall as well as some of the highest temperatures ever recorded. It started in July, then August, then September and continued into October. Gardeners were struggling to maintain their gardens with the unseasonable dry periods and temperatures in the 90s. A huge challenge for gardeners were their container plantings. By mid to late summer, many plants in containers, having grown all summer, had filled the pot with roots and thus needed a daily watering. Sometimes once a day was not enough. Plants were wilting, leaves were scorching and some plants, especially those that were newly planted, did not survive. So it was not only the plants that were stressed, but the gardeners as well.
Broadleaf evergreen plants like rhododendrons, azaleas and kalmia were hit particularly hard. These are plants that are accustomed to a cooler environment and enjoy some protection from the hot afternoon sun even in a “normal” summer season. In my garden some of these plants, even in a partially shaded section of the garden, would have very wilted leaves by late afternoon in spite of being irrigated earlier in the day. In most gardens broadleaf evergreens like these are established plants in the ground, not in containers, and so amending the soil in the root zone is not possible. .
Since the weather is a great unknown, I am going to do some preparation to prevent this kind of damage just in case there is a repeat summer of heat and dry like last year. One thing that we can all do is to walk through our garden at this time of year and take a good look at the plants that suffered last summer. Perhaps they are not in the best location and would perform and thrive much better if they were moved. Since we have had rather predictable summers during the previous years, I think that many of us, including myself, have stretched the “zone” where some of these shade-loving plants are planted. If something does need transplanting, this is an ideal time to plant many evergreen plants.
Relocating Broadleaf Evergreens
If a decision is made to transplant some of these broadleaf evergreens, now is your perfect opportunity to amend the soil in the new location. My favorite soil amendment is Black Gold Garden Compost Blend as this can be worked into the soil around where the new plant will be placed. This will then help to hold moisture in the soil and can help alleviate some of the drying that can occur with lack of water. On other existing plants that are not going to be transplanted, try working into the top 1-2 inches of soil some Black Gold Just Coir. That has wonderful water-holding capabilities.
Don’t wait until summer arrives to do these chores. By being a step ahead, it is possible to keep your plants in an overall healthier condition. And even if the upcoming summer is not a scorcher, your plants will thank you for the extra care you gave given them.
When is an azalea a rhododendron? Always! The American Rhododendron Society website explains: “Rhododendrons and azaleas belong to the genus Rhododendron in the heath family (Ericaceae). Other members of this ornamental-rich family include heaths [Erica spp.] and heathers [Calluna spp.], blueberries [Vaccinium spp.], mountain laurels [Kalmia spp.] and many other important ornamental [and edible] plant genera.
Living in the Pacific Northwest, we have an abundance of rhododendrons to provide spring color. While there are many hybrids to chose from, one of my favorites is a species called Rhododendron yakushimanum ‘Yaku Angel’. This has wonderful white, felt-like new growth and soft brown indumentum (under surface of leaves) with a velvet-like touch. The flowers are a light pink in bud and open to white. This is a beautiful shrub in the garden at any season, whether in bloom or not.
Rhododendrons like a moist soil and using Black Gold Garden Compost Blend is ideal. Fertilize now with fertilizer formulated for acid-loving plants. The photo is from a plant in my garden taken in late April. Rhododendron Yaku Angel