PLANTING—Full sun is the ideal location for most dahlias. The exception is hot climates. In these areas it is best to select a spot with morning sunlight, but not the hot afternoon sun. Dahlias are usually planted about the same time as vegetable gardens. Delay planting until all danger of frost is over and soils have warmed up. For most climates, this is Mid-April through May. In warmer, southern states dahlias can be planted in March. A well-drained deep soil works the best. Lay tubers flat with the eye pointed up. Plant 3-6 inches deep 18-24 inches apart. Bone Meal or a low nitrogen fertilizer such as 5-10-10 can be added at planting time. Too much nitrogen can cause excessive vegetative growth and fewer blooms. Do not use bark dust on dahlia beds. For container gardening, we suggest garden soil or a mixture of garden and potting soil. The shoots take 2-4 weeks to emerge. Slugs and snails can be a major problem. We recommend putting slug bait out at planting time and follow up as needed. Taller varieties of dahlias will need to be staked. To avoid damaging the tubers, stake before or at planting. The moisture in the spring soil is sufficient to promote growth. Do not water the tubers at planting time. I cannot stress enough as to how important it is to NOT WATER after planting the tuber. Over watering early in the season can rot the tubers.
SUMMER CARE—Once the weather has warmed up and the top growth has emerged, you can begin to water. A deep watering weekly should be adequate. When your dahlia plants are 12-20 inches tall with no more than 4 sets of leaves, cut or pinch the center shoot. This produces shorter, bushier plants with more flowers. Removal of old blossoms promotes more blooms and keeps the plant growing vigorously. It is best to cut flowers for bouquets early in the morning or late in the evening. To set the blooms for longer lasting enjoyment, put the stems in 2-3 inches of very hot water (about 160 degrees) and allow to cool for one to two hours. Aphids, cucumber beetles, earwigs and gophers can be a problem during the growing season. Check your garden store for control of these pests.
FALL CARE—In cold climates it is best to dig and store the tubers for winter. Freezing temperatures and excessive moisture can cause rot. In mild climates, dahlias can be left in the ground to re-grow the next season if they are protected from frost. Dig tubers two weeks after the first frost or wait until the middle of November. Wash clumps and let them dry (not in hot sun). Clumps can be divided before storage or in the spring. Protect from freezing. A storage area about 40-50 degrees is ideal. Tubers or clumps can be placed in vermiculite, sawdust, or peat moss to prevent shriveling. This is not the method that works for me on the Peninsula. A tuber needs to have an eye for it to produce a plant. The eyes are located next to the stem. They may be easier to see in the spring.