Dahlias will grow almost anywhere and are very forgiving, easy to grow garden plants. They prefer full sun but can tolerate some partial shade. Dahlias are deer resistant and naturally healthy and strong plants. They thrive in sunlight: the more sun, the bigger the flowers! There are a few things to know in order for your Dahlias to thrive.
Pre-sprout your tubers
In cooler climates, Dahlias can be planted indoors, 4 to 6 weeks before the last frost date. Fill 1 or 2 gallon flowerpots or garden containers with slightly moist growing mix. Place the tubers in the flowerpots or plant containers with the neck or sprouts facing up, cover with 2 inches of soil and set them in a warm place with good light and hold off on watering until you see leaves.
Choose a location
Try to select a location that receives at least 6 hours of sun and is sheltered from the wind. Dahlias like to grow in well-drained and slightly acidic soil. If soil holds standing water for more than 24 hours after a heavy rain, it is normally a sign of poor drainage.
Plant the whole clump, no need to divide further. We recommend leaving the clump intact for the first growing season. Plant with the stem base facing upward, with the tubers pointing down or laying sideways. Plant just a few inches below the surface so the sun can warm the soil which allows the eyes to sprout. When the soil temperature is warm enough, your Dahlias should sprout through the soil within 3-5 weeks. If the soil is too cold, it will stunt the growth and the tuber may end up rotting.
Space your plants so they have enough room for air circulation. Allow 16″-20″ between bulbs to avoid overcrowding. For best performance, plant taller varieties behind the shorter varieties so the shorter ones don’t get shaded out by the taller stalks, causing them to produce fewer and smaller blooms. Dig a small hole of 4″-6″ deep and gently lay the tubers on their side. If the roots already have sprouted, make sure the eyes are facing upward. Back-fill the hole without tamping it down and without watering.
Water, don’t over-water
Dahlias hate to sit in water and will rot quickly if they don’t have any foliage to dissipate the moisture. If the forecast calls for extended periods of rain you’re better off waiting than ending up with rotted tubers! For the same reason, it is best to NOT water your Dahlia tubers until the first shoots have sprouted. Tuber clumps holds ample moisture and nutrients to feed the new shoots until they surface.
How and when to fertilize
When planting in garden beds consider adding compost and some peat moss to supply nutrients and improved drainage. In larger flower pots, patio planters or garden containers, start with any balanced commercial potting soil. Adding a slow release fertilizer to feed your plants all season is an easy way to ensure sufficient nutrients for a great flower display. While Dahlias do require some nitrogen, too much nitrogen fertilizer can cause the plants to be poor flower producers. Fish Bone Meal (5-13-0) is a good fertilizer when planting your tubers to see your Dahlias off to a good start.
We have our own little helpers here at the farm when it comes to organic pest control, but you want to keep bugs and grubs to a limit at least while the plants are young and still trying to establish roots and foliage.
Pinching and supporting your plants
As your Dahlias grow, remove any broken or damaged foliage. Good air circulation is important to prevent disease and infestation, so it’s a good idea to strip the bottom leaves once stems have reached 12″-18″ height and have developed 5 or 6 side shoots. Pinch the shoots when they are 18″ tall to encourage branching and more prolific blooming. If you prefer taller stalks with larger blooms, forgo the pinching and thin out some of the side shoots instead. This method will require more robust staking to support the tall stalks, but the bigger blooms will be rewarding.
Time for harvesting
Your Dahlias will continue to bloom prolifically right up until the first frost. The first nippy frost will kill the flowers and greens, but not the tubers. You want to wait about two weeks to let the foliage die off completely before carefully digging up the clumps, if you plan to re-grow them next year. Remember to label the tubers as to variety; it’s easy to forget.
Wash the tubers gently and let them dry away from direct sunlight. Once the tubers have dried, you have a few choices. At Fleur Farm we use two methods of storing. For the first method, you have to start dividing the clumps into single tubers, then dip each tuber in anti-fungus powder and wrap them individually in saran-wrap. This method saves a lot of storage space, and prevents molded tubers for contaminating other tubers. For the other method, we divide the clumps into quarters and store these on a bed of peat moss in open containers. The key to success is to store the divided tubers in a dark place at 40F temperature, in 50% humidity.
Take a break!There’s no question about it: we love it out here, but farming is hard!! Be kind to yourself and know when to take a break.