Dahlias come in countless varieties, adding vibrant colors and exotic blooms to a summer garden or landscape. Dahlias are surprisingly hardy perennial flowers that grow from tubers. You can plant dahlias in early or mid-spring, when the soil has warmed up and all chance of frost has passed. Dahlias can be planted in flower beds, in borders or in containers, just as long as they receive full sunlight, fertile soil and lots of water throughout the growing season.
Water your dahlias slowly and deeply two or three times each week throughout the growing season. Ideally, you should water the dahlias using a sprinkler or by laying a slowly trickling hose beside the dahlias for about 30 minutes.
Feed your dahlias with a low-nitrogen fertilizer, such as a 5-10-10 or a 10-20-20 NPK (nitrogen-phosphorous-potassium) fertilizer. Apply the fertilizer according to the dosage instructions on the label, first within one month of planting the dahlias and again about one month later.
Prune back the central leader stem of your dahlias to keep the plants no taller than 18 to 20 inches, or pinch the stem back to right above the third set of leaves. Doing so will encourage the dahlias to grow in bushier and will promote stronger stems.
Control snails and slugs that infest your dahlias by setting out bait beginning two weeks after planting the tubers and throughout the growing season. Spray your dahlias with neem oil or an appropriate insecticidal spray to control other pests, such as earwigs, cucumber beetles and spider mites.
Protect your dahlias in winter by cutting back the central stems down to the ground right after the first killing frost. Cover the ground over the dahlia tubers with plastic sheeting, adding a 3-to-4-inch layer of mulch or soil on top of the plastic.