The #1 Mistake Beginners Always Make When Growing Dahlias, According to a Gardening Expert

If the idea of “love at first sight” was ever proven true, it would surely be at the moment one first looks at a dahlia. These vibrant blooms, which are native to Mexico, command attention in any setting, from bountiful home gardens to a bustling farmers’ market, with their impressive flower heads spanning every hue from delicate buttery yellows to deep, rich burgundies. They possess a beauty that not only gives gardeners pause but also beckons them to weave these flowers into their own gardens.

This sentiment is shared by Deborah Stone, the founder of the Alabama-based Stone Hollow Farmstead. She explains how she fell instantly in love with dahlias during a trip with her daughter, Alexandra. That influential trip marked the beginning of their own dahlia journey on the farm.

Stone says, “Alexandra and I traveled to Skagit Valley [in Washington] and visited Floret Flowers for a weekend of education on cut flowers. Part of the class was an introduction to dahlias, and we were just blown away. We came home and purchased 500 tubers, dove in head first, and we have never looked back. Best decision ever.”

Stone Hollow Farmstead has become the go-to source for all things related to dahlias, boasting an impressive collection of tubers, intensive growing workshops, and a Dahlia Day where guests can see the flowers in full bloom on their family farm.

Dahlias are plants that often intimidate beginners, as they grow from tubers and can be quite sensitive. So, we asked Stone for her essential tips on cultivating dahlias in your own backyard. With this valuable advice, we are confident that you’ll be falling in love with dahlias all over again.

How to Grow and Care for Dahlias

Prep your soil and put in the stakes.

gettyimages-513756945

It should come as no surprise that lush blooms require diligent prep work, particularly in their planting location. Dahlias demand full sun, needing at least 6 hours of sunlight per day, and they flourish in hardiness zones 8 and higher as a perennial (though, gardeners can still grow them in zones 3 to 7 as an annuals). In warmer climates, where the summer heat can be intense, consider a spot in your garden that receives morning sunlight and afternoon shade. You might also want to select a heat-tolerant dahlia variety that grows rapidly. Stone’s favorites for beginners include Miss Amara, Rebecca Lynn and Baron Aunt Dorothy.

Stone notes that dahlias do not tolerate waterlogged roots and recommends planting them in well-drained and sandy soil. Additionally, dahlias tend to thrive in slightly acidic soil, so adjusting the pH to the ideal range of 6.5 to 7 with fertilizer may be necessary. If you’re unsure about your soil’s pH or fertility levels, Stone advises reaching out to local gardening organizations or an extension service to conduct a soil test. Stone adds, “Solid testing will really help you get it right and save you money because you will know what inputs your soil needs to grow these heavy-feeding plants.”

After preparing the soil properly, it’s a good idea to set up stakes, especially since tall dahlia varieties can become top-heavy and some even have vine-like qualities. Stone suggests placing bamboo stakes approximately 24 to 36 inches apart within your planting area. This spacing allows each dahlia plant enough room to grow and move freely. With the stakes in place, you’re ready for the fun task of planting.

Gaia Green 2-8-4 Power Bloom Fertilizer

$29.46

6 ft. Natural Bamboo Eco-Friendly Garden Plant Stakes

$24.00

Don’t water your tubers right away.

gettyimages-1405005887

To ensure the best start for your dahlias, it’s important to begin planting your tubers after the last frost has passed and when the soil has warmed. Typically, this falls between mid-April and May in many regions. However, Stone advises consulting the USDA Hardiness Zone map to determine the date of the last expected frost in your specific growing zone for a more accurate planting time.

When planting dahlias, dig a hole about 4 to 6 inches deep. Ensure that the tuber is placed with the eye or sprout facing upward, as this is where the stem will emerge. Once placed, gently fill the hole with soil. Stone advises against watering the tubers immediately and recommends waiting until you see sprouts. The tubers can rot easily if overwatered which is a common mistake among beginners. After the dahlias have sprouted and produced their first set of leaves, it’s time to water them thoroughly. To maintain healthy growth, dahlias require consistent watering, which typically means watering them 3 to 4 times a week.

Pinch your flowers for better blooms.

gettyimages-1180051442

It can be difficult to convince new dahlia growers about the benefits of pinching, yet this practice is crucial for encouraging the plant to develop more vibrant and fuller blooms. When your dahlia reaches approximately a foot in height, you should pinch off the crown bloom. This action allows the plant to produce additional laterals and flowers, enhancing its overall bloom yield in the long term.

For gardeners aiming to create a striking focal point or to cultivate larger blooms, Stone suggests disbudding or limiting the lateral buds, which directs the plant’s energy towards developing a primary central bloom. However, Stone points out, “When you do this you also reduce the number of blooms you will get, so it’s really about finding balance.”

It’s in these early stages you may also want to apply organic miticide and pesticide to deter any unwanted visitors. Stone says, “We do preventative sprays, usually once the sprouts have two pairs of true leaves—we don’t wait on the mites to show up. Also when you plant, go ahead and put Sluggo down to prevent the caterpillars and slugs from consuming your baby plants.”

Monterey Sluggo Wildlife and Pet Friendly Snail & Slug Killer

$28.86

Embrace their short beauty.

gettyimages-1071368004

The lifespan of cut dahlias is relatively short, so it’s important to handle them with care. For the best results, harvest dahlias during the cooler parts of the day, either early morning or evening, as this practice can help maintain their freshness. After cutting, many experts suggest plunging the stems immediately into hot (but not boiling) water. The rationale behind this technique is that the hollow stems of the dahlias will absorb water more effectively, extending their vase life. Generally, cut dahlias last between 4 to 7 days after being harvested. To maximize their beauty, remember to change the water daily in the arrangements you create.

Niwaki Garden Scissor Gift Set

$78.00

Save your tubers.

gettyimages-1281956563

At the close of the growing season, you can either dig up the dahlia tubers for next year’s planting or leave them in the soil. In hardiness zones 8 to 10, it might be possible to leave the tubers in the ground successfully, though it is still recommended to remove and divide them every few years.

For gardeners in zones below 8, it’s better to dig up the tubers to protect them from freezing and rotting over the winter. Once dug up, gently rinse the tubers with water, let them dry, and store them in a mix of vermiculite and peat. By springtime, the tubers should be ready for replanting.