Dahlia Care & Growing
Storing Dahlia Tubers
The ideal temperature for storing your dahlia tubers is between 40°F and 50°F. If the temperatures in your storage area drop below 32°, your tubers will freeze and then rot and will no longer be viable. Use an unheated basement, root cellar, or an insulated garage that does not freeze.
Dahlia tubers can be stored in many ways. You can layer tubers in cardboard boxes or plastic bins filled with a breathable medium like vermiculite, peat moss, wood shavings, or dry sand. As they are packed, ensure the tubers do not touch each other.
Divided tubers can also be Individually wrapped in plastic wrap. This ensures no two tubers touch and this method effectively locks in moisture.
You can also store whole dahlia clumps, versus dividing your clumps into individual tubers. Simply place your whole, unwashed clumps in plastic bags or crates with some wood shavings or peat moss.
Throughout the winter, inspect your dahlia tubers every few weeks for signs of trouble. Remove any mushy or moldy tubers immediately to prevent the spread of rot. If tubers look wrinkled, lightly mist the storage medium to maintain hydration.
Planting Dahlia Tubers
When planting dahlia tubers, wait until the soil reaches about 60°F and all danger of frost has passed. Choose a location that gets at least 6–8 hours of direct sunlight. Avoid heavy clay soil if possible and amend your soil to improve drainage if necessary. Dig your hole or trench 6 inches deep and add a handful of bonemeal or a balanced fertilizer (like 5-10-10). Lay the tuber horizontally with the eye (the small bump or sprout at the "neck" where it meets the stem) facing upward. Space tubers 12–24 inches apart, depending on the variety's mature size. For varieties taller than 3 feet, insert a sturdy stake at the time of planting to avoid damaging the tuber later.
Do Not Water Immediately: Avoid watering until the first green shoots emerge from the soil to prevent the tuber from rotting. Once the plant is about 12 inches tall, pinch off the top 3–4 inches of the main stem to encourage a bushier plant with more blooms.
Slugs and snails love dahlias! Sprinkle slug bait immediately after planting to prevent damage to new shoots.
If you have a short growing season, you can "wake up" tubers by potting them indoors 4–6 weeks before the last frost
Caring For Dahlia Plants
The watering needs of your dahlias will change as they grow. Do not water newly planted tubers until you see green shoots poking through the soil; overwatering at this stage often causes the tubers to rot. Once your dahlias have grown and are getting established, you’ll need to provide a deep soak 2 to 3 times a week. In very hot climates, you may need to water more frequently to keep the soil consistently moist. It is always best to water only at the base of the plant (no overhead watering) to keep foliage dry and prevent fungal issues like powdery mildew. Drip irrigation at the base of your dahlias is an ideal watering method.
Dahlias are "heavy feeders”. Use a fertilizer with low nitrogen but high phosphorus and potassium, such as a 5-10-10 or 10-20-20 formula. Start fertilizing about 30 days after planting and continue every 1 to 2 weeks until late September. Avoid high-nitrogen fertilizers, which produce lush green leaves but few flowers. We prefer a fish emulsion fertilizer applied to the leaves with a sprayer and we typically add in unsulphured blackstrap molasses, that boosts plant health, improves Brix levels, and acts as an organic pest deterrent.
To maximize flower production, you’ll want to pinch your dahlia plants. When the plant is 12–16 inches tall with 4 sets of leaves, snip off the main center stem. This forces the plant to branch out, creating a bushier shape with more blooms. You’ll also want to regularly deadhead spent flowers to encourage the plant to keep producing new buds rather than setting seed.