“How and when do you pinch dahlias to encourage fuller growth?” Question from April of Dresden, Tennessee
Answer: Once your dahlias are close to their final height (which depends on the variety) and have ample foliage, you can pinch or trim them back to encourage fuller growth, more branching, and more flowers. Just be sure to wait until they are large and full enough to bounce back nicely.
I always recommend cutting them back just above a branching stem node (see adjacent image). New branching stems will arise from the node. I also recommend using sharp shears to do the job rather than pinching (Corona Flora Scissors work very well). Cleaner cuts help plants heal and revive more quickly.
“What kind of potting soil should I use for Dahlias, Asiatic and oriental lilies, and begonias?” Question from Luciana of Portland, Oregon
Answer: Each flowering plant has some distinct needs when it comes to soil moisture, pH, and quality. The right kinds of fertilizers also help these flowers bloom at their best.
Soil and Fertilizer for Asiatic and Oriental Lilies
Lilies of all types grow best in soils that are well-drained and rich in organic matter. The ideal pH should be a little more acidic (5.5 to 6.5), but neutral soils are also tolerated. Once again, I recommend our Black Gold® All Purpose Potting Mix in addition to another of our OMRI Listed mixes, Black Gold Natural & Organic Ultra Coir, which is rich in organics but drains well. Here, it is best to choose a fertilizer specially formulated for summer bulbs. These tend to be balanced fertilizers with added bonemeal, and there are many fine choices on the market.
Soil and Fertilizer for Begonias
Fast-draining soils that are light and fertile are preferred by begonias. Their tubers or fibrous roots are prone to rot, so soils that hold onto water too well can be detrimental. Once again, a slightly acid pH (5.5 – 6.5) is needed. Black Gold® Natural & Organic Potting Mix is a good soil choice. Adding a little extra Black Gold Perlite for added drainage is also recommended. Proven Winners Premium Continuous Release Fertilizer helps boost flowering and performance in begonias. The occasional addition of Proven Winners Premium Water Soluble Plant Food will also help boost flowering.
“I have tried everything to grow Dahlias. They come up sometimes to about 1ft and never bloom.” Question from April of Dresden, Tennessee
Answer: I am sorry to hear that you are having trouble with your dahlias flowering. There are several factors that impact dahlia blooming, including light levels, fertilizer, and dahlia type. First, provide them with full sun–eight or more hours per day is best. Feed your plants with a quality fertilizer formulated to encourage flowering to boost blooms. Finally, choose more compact dahlias with a free-flowering nature. Try varieties in the Gallery Series, which are more compact and flower nonstop. Dahlias in the Happy series are also outstanding when it comes to repeat bloom. Happy Single Flame is especially pretty with its hot pink and yellow single blooms. For more information, I encourage you to read the following blog and watch our video about growing Dahlias to perfection. (Click here to read All About Growing Dahlias.)
“How do u get dahlias to grow? I just get two scrawny limbs that never a bloom.” Question from April of Dresden, Tennessee
Answer: That must be frustrating! Southern gardeners often struggle with dahlias, unless they live in mountainous areas where summers are cooler. This is because most dahlias grow best under milder growing conditions and melt in high summer heat. Thankfully, there are select varieties tolerant of southern heat.
Either way, let’s start with the five basics that dahlias need to thrive:
1. Full to partial sun (6-8 hours of direct sunlight each day.)
4. Regular water (Soil should be kept just moist, never too wet or dry.)
5. During really hot weather, shade dahlias during the hottest time of day
Then there’s choosing the right dahlia. The Dahlia Society of Georgia has the best list of heat-tolerant dahlias for southern gardeners (click here to view the list). My favorite dahlia on their list, called ‘Bodacious’ (shown above), has big, beautiful red and creamy yellow blooms.
Follow these growing instructions and choose only heat-tolerant dahlias from the attached list, and your dahlia growing will really improve! We also suggest you watch our video on Dahlia growing. It provides even more in-depth instructions on how to make the most of your dahlia growing.
Dahlias are some of the most beautiful garden flowers for cutting and color. Here’s everything you need to know to grow beautiful dahlias and store them through winter.
Dahlias come in all forms, from monolithic 12” dinnerplate monsters to tiny 2” pixie pincushion blooms, and colors—pretty much any shade except for true blue. So, you can never love just one. They thrive in the cooler seasons of early summer and fall and offer a botanical extravaganza of floral beauty with over 50,000 named cultivars and 20 wildly diverse forms. (Visit the American Dahlia Society (ADS) website to learn more.) Some are compact and perfect for containers while others are eight-foot monsters. All are wonderful and distinct in their own right.
Dahlia ‘Mark Lockwood’
Dahlia Origins
The dahlias we grow in our gardens are hybrids of three high-altitude Mexican species, Dahlia coccinea, D.pinnata, and D. rosea, which were first collected in 18th-century Mexico and first cultivated in Mexico City under the care of the Spanish botanist, Vicente Cervantes (1755 – 1829). They were exported to the Royal Gardens of Madrid, Spain, in 1789, and began to appear in gardens across European shortly after. They popularized in the middle of the Victorian era (1850s-1860s), and by the early 1900s, there were thousands of varieties available across Europe and North America.
Dahlia ‘Show ‘N’ Tell’
Hybridizers come up with new dahlias each year. Many home gardeners prefer compact, heavy flowering border dahlias that don’t need staking. Five great performers recommended by Steve Nowotarski, the head of the ADS border dahlia trials, recommends the following three varieties: the party-pink decorative ‘Melody Pink Allegro’, peppermint-striped ‘Princess Paige’, and magenta cactus-flowered ‘Pinot Noir’. For cutting, taller, long-stemmed varieties are best, such as the vibrant red and yellow ‘Show N’ Tell’, classic pink cactus-flowered ‘Park Princess’, and ‘Mark Lockwood’ with its lavender pincushion blooms.
Dahlia ‘Taratahi Ruby’
Growing Dahlias
Due to their cool, high-altitude origins, these sun-loving garden flowers grow best when weather is cool and humidity is moderate to low. When days are warm and nights are cool, they bloom and grow best. There is no real trick to getting their soil right. Like many plants, they excel in slightly acid to neutral, friable, organic-rich soil with very good drainage. Planting contained specimens in quality potting soil, such as OMRI-Listed Black Gold Natural & Organic Potting Soil with RESiLIENCE®, or heavily amending in-ground plantings with Black Gold Garden Compost, will ensure great rooting conditions. Keep the soil lightly moist, not wet, and feed flowering plants with a low-nitrogen fertilizer formulated for flowers.
Many dahlias are tall and require support—low tomato cages are perfect. Caging offers tall, large-flowered varieties needed support during heavy rains and wind –keeping top-heavy plants from toppling. Shorter varieties are easiest to tend as they don’t require support. All plants, tall or short, should be deadheaded regularly to keep new blooms coming until frost.
Tall dahlias staked in a tomato cage.
Overwintering Dahlias
Dahlias are tender perennials able to survive winters in USDA hardiness zone 8. In colder zones, their tuberous roots must be dug and stored indoors through winter. Dig dahlias after their tops wilt following the first light frost. When digging tubers, keep then intact and be careful not to damage their necks as this is where next year’s buds will appear. Gently clean and dry the tubers before storing them. Pack in a dry peat/vermiculite mix and store in a cool, dry basement, garage or root cellar no colder than 40 degrees Fahrenheit.
Once the threat of frost is past, plant again in spring to a depth of four to six inches. In cool weather, refrain from watering tubers directly after planting to avoid tuber rot. On hot summer days, be sure to water them regularly and provide potted specimens with shade during the hottest times of the day. Care for them well, and you will have wonderful garden color and cut flowers, even during the hotter days of the month.
Another great perk about dahlias is their value. These beautiful garden flowers are very reasonably priced. Swan Island Dahlias is a great one-stop-shop for hundreds of fantastic varieties befitting any garden. Plant a few this year and after one season, you will be hooked!
Answer: Once your dahlias are close to their final height (which depends on the variety) and have ample foliage, you can pinch or trim them back to encourage fuller growth, more branching, and more flowers. Just be sure to wait until they are large and full enough to bounce back nicely.
