“September is dressing herself in a show of dahlias and splendid marigolds and starry zinnias…” Oliver Wendell Holmes, Sr.
When & Where To Plant
For best results, dahlias should be planted from mid April through May when ground temperature are about 60 degrees. In general, about the same time you would plant your vegetable garden. Dahlias need a sunny location to thrive. An area that receives at least 8 hours of direct sunlight is best. Less sun equals taller plants and less blooms.
Soil Preparation & Planting
Ground should be warm, well drained at planting, and in an open sunny location. If you have a heavier soil, add in sand, peat moss or bagged steer manure to lighten and loosen the soil texture for better drainage. Bone meal is ideal at planting time, put a small handful in the hole and work in well before planting tuber. PH level of your soil should be 6.5-7.0, slightly acidic. Do not amend dahlia beds with purchased top soils unless you are sure that it has not been treated in any way for weeds. Compost of any type should be avoided. Lay the tuber horizontally 4-6” deep, about 18” to 24” apart, and then cover with soil. DO NOT WATER TUBERS AFTER PLANTING!! Please wait to water until after the sprouts have appeared above the ground. The exception will be in hot climates, where they should be watered very lightly. Do not use bark dust or mulch to cover dahlias, as it does not allow the soil to warm up or tubers to sprout properly. This is a good time to apply snail and slug bait to protect the new sprouts.
Staking
We recommend staking any dahlias that will reach 3 feet or taller. Any staking product will work, please check your local garden center – i.e. tomato cages, metal rods, or bamboo stakes.
Watering
Most areas have enough rain to fill dahlia water needs until the sprouts appear above the ground. After dahlias are established, a deep watering 2-3 times a week for at least 30 minutes with a sprinkler, more required during warmer dryer weather. Hotter climates will need to water more often as conditions require. Proper watering promotes proper blooming. Hand watering is not enough.
Fertilizer
Dahlias require a low nitrogen fertilizer, such as used for vegetables. We recommend high percentage potassium and phosphorus fertilizers such as a 5-10-10, 10-20-20, or 0-20-20. First applications should be within 30 days of planting and repeated again approx. 3-4 weeks later. One of the biggest mistakes made with dahlias is over feeding them. Avoid compost and high nitrogen water-soluble types as they promote weak stems, small blooms, or no blooms, and tubers that rot or shrivel in storage.
Digging
Digging should be done about 2 weeks after a killing frost, the plants will turn brown if frosted hard enough. Tubers dug too early are still “green” and will not store. It is safe to dig by mid-November without a frost. Cut the stalk off to about 6”, gently lift tubers with a spade or pitchfork carefully so as not to break the necks. Wash dirt from the roots and allow to air dry, protected from the elements for about 24 hours.
Winter Storage
Use a storage medium such as slightly dampened Peat Moss, Sand, or Pet bedding material (sawdust/shavings). Tubers should be stored in crates or cardboard boxes. We recommend lining the containers with 10-12 sheets of newspaper. Start with your packing medium in the bottom and layer tubers and medium until the container is full. Never store in sealed plastic bags or plastic containers. Store in a cool, dry area (temp. of 40-50 degrees). Too warm they will wrinkle/shrivel and too cold they will freeze/rot. Please check your tubers once a month throughout the winter months.
Dividing
Can be done in the fall, or in the spring. If eyes are difficult to see, we suggest diving the clump into halves or quarters. Use a hawk bill shoe knife (available pg. 62 of our catalog) or sharp knife to cut through the tubers. The eyes will be located on the center stalk and each root must have an eye in order to grow. Not all tubers will have an eye. Cut surfaces should be allowed to dry overnight before storing, or planting. Different varieties will produce different sizes and shape tubers.
From Swan Island Dahlias