Dahlia plants grow from tubers planted in the ground like potatoes. They are not bulbs or rhizomes. Some dahlias are grown from seed and new varieties are usually developed from seed.
Do: Buy your tubers from reputable dahlia growers or nurseries. Quality makes a difference.
Don't: Buy cheap packaged dahlia tubers from overseas at thrift garden outlets. The flowers seldom resemble the pictures.
Do: Buy tubers with visible eyes located at the stem end of the tuber. Unlike potatoes which have eyes all over, dahlia tuber eyes are only found near the end where the tuber attaches to the plant stem.
Don't: Buy a tuber that doesn't have an eye showing unless the seller or an expert can locate it for you. (They are sometimes difficult to see)
Do: Buy plump, healthy looking tubers with no sign of decay.
Don't: Purchase shriveled, skinny tubers or those showing any sign of rot or decay.
Do: Buy your tubers from a local dahlia society during their annual tuber sale. The tubers are usually the latest top varieties. Club members are there to answer your questions and the proceeds go to help dahlia societies promote this beautiful flower.
Do: Till or turn your soil about a month before planting.
Do: Add lots of organic matter to your dahlia beds (aged manure, peat moss, leaf mold, and compost are excellent).
Do: Till or turn your soil a week before planting.
Don't: dig a hole in hard ground and plants your tubers. Dahlias need lots of water. They send out thousands of tiny feeder roots and they need loose well-drained soil to do well.
Don't: use fresh manure, especially chicken manure, which will burn and damage or even kill your plants.
Do: Plant your dahlias after all chance of frost has passed. Usually from the end of April to mid-May in most areas.
Don't: Plant too early. Dahlia tubers are susceptible to rotting if the soil is too wet. They can also freeze if a late frost hits their new shoots.
Do: Plant in a sunny location with a minimum of 4 to 5 hours of sunlight per day. Six to eight hours is preferred.
Don't: Plant dahlias in the shade. The plants will be gangly and the blooms weak.
Do: Plant in well-drained soil.
Do: Plant your tubers 4 to 6 inches deep and next to a sturdy stake. Any dahlia plant taller than 2 feet should be staked and tied to keep it from collapsing during inclement weather.
Do: Have your stakes in the ground before you plant your tubers. Place stakes 24 to 30 inches apart.
Do: Protect from a late frost.
Do: Protect against slugs and snails by baiting or by killing with a spray solution of 1 part ammonia to 1 part water.
Do: Cultivate lightly while plants are small.
Don't: Cultivate heavily with a hoe or tiller after plants are a foot tall. Dahlias are surface feeders and their root systems will be damaged.
Do: Tie your plants to their stake as they grow.
Do: Top or pinch the growing tip of all large flowering (4 inch bloom or larger) dahlias after they have developed three to five sets of leaves. This produces more early flowers and a compact bush.
Don't: Let your dahlia plants grow unchecked and gangly.
Do: Fertilize with a higher nitrogen organic fertilizer when plants are 6 inches to a foot tall.
Do: Apply a 2 to 4 inch layer of mulch (compost, straw, grass clipping) to prevent weeds and to keep moisture levels high.
Do: Disbud your blooms (remove two side buds at each budding tip) to encourage growth and control plant size.
Don't: Let all the blooms develop without disbudding. Flowers will be weaker with shorter stems.
Do: Deadhead (remove) old or spent blooms.
Do: Water deeply every four or five days as the season starts to get hot.
Don't: Water lightly every day.
Do: Fertilize with a low or no nitrogen fertilizer (0-20-20) to encourage flower and tuber development.
Don't: Fertilize with high nitrogen fertilizers once blooms begin to develop.
Do: Continue to control slugs, snails and insects.
Do: Cut lots of flowers for the home, office, and for friends. Cutting encourages more growth.
Do: Take in a local dahlia society show in August or September. They are breathtaking.
Do: Enjoy your flowers until the first frost kills back your plants.
Do: Leave tuber clumps in the ground if you have good drainage and cover them with 3 to 4 inches of mulch for protection from frost. Clumps should be divided every third year for nicer, bigger flowers and stronger stems.
Do: If you are going to dig your dahlias, cut off stalk to 3 or 4 inches above the ground and leave in the ground for a week or two to allow eyes to set before digging out the clumps.
Do: Begin cutting down and digging by November even if no killing frost has taken place.
Do: Carefully dig completely around each tuber clump with a shovel or garden fork and lift gently to avoid breaking the tuber necks. After removing from the ground carefully hose the dirt from the tuber clump, clip off all feeder roots with garden scissors and then let dry overnight.
Don't: Pull tuber clumps from the ground using the stalk as a handle. This will break many thin-necked tubers.
Do: Carefully divide clumps in half by splitting with pruning shears.
Do: Carefully cut off individual tubers from each half using hand pruners, garden scissors and a sharp knife. (It is advisable to wear a protective glove such a meat cutters fillet glove when working on your tuber clump with a sharp knife).
Do: Make sure each tuber has a viable eye that you can see - sometimes it helps to use magnifiers for this work. The tuber eyes will only be located at the swell of the crown of the tuber clump near the stem.
Don't: Cut the tubers from the clump at the beginning of the neck or it will have no eyes. Eyes are only located near the stem.
Do: Soak you individual tubers in a bleach and water solution for 15 or 20 minutes to kill all bacteria. Use a solution of 1-cup bleach to 3 gallons of water. Don't leave tubers in the solution too long.
Do: Allow tubers to dry for two or three days before storing. Dry on newspapers in a cool, dark place.
Don't: Dry in the sun or a warm location. Drying on concrete draws the moisture out of the tuber.
Do: Label your tubers before storing with a permanent marker or No blot pencil. If you don't know the name of the dahlia you might want to just indicate the color of the flower.
Do: Store your cut tubers in plastic bags with a few handfuls of vermiculite or wood shavings or potting soil. An alternate storage method that some people use is to roll tubers up in a long strip (2 or 3 feet) of plastic wrap, making sure that individual tubers are not directly touching each other. Five or six tubers can be wrapped together using this method. Fold over the end and secure with masking tape and label.
Do: Keep bagged or wrapped tubers in a dark cool storage area where they will not freeze. A crawl space, root cellar or old refrigerator is a great winter storage location.
Don't: Store in a warm place where temperatures will rise above 50 degrees for a long period or your tubers may rot or start sprouting too early.