DAHLIA CARE
Growing dahlias at home is a relatively easy and rewarding way to add color and texture to your garden from midsummer through fall.
Planting
If possible, get your soil tested by your local extension office several months before planting your dahlias. You'll receive a report indicating your current soil's nutrient levels as well as the exact amount of each nutrient that needs to be added back to the soil for your plants' optimal growth.
(It's easier than you think and will make the biggest difference for the growth and health of your dahlia plants.)
Where: Dahlias appreciate well-draining, loose soil and at least 6 - 8 hours of full sun. If you live in an especially hot climate, they do well with afternoon shade.
When: Plant in late spring after all danger of frost has passed and the soil has warmed to 55 - 60 degrees.
How: Dig a 4 - 6" deep hole and place the tuber horizontally with the eye (sprout) facing up if possible. Cover with soil and place a plant label.
Space dahlias 12 - 18 inches apart.
Sprinkle Sluggo around the planting area or the slugs may enjoy your sprouts before you see them.
Don't water dahlia tubers until you see sprouts emerge from the soil (usually takes 2 - 4 weeks after planting).
Staking: Dahlias appreciate staking to help support their blooms. You can use a tomato cage or tie the main stalk to a wood or metal stake.
For a large amount of dahlias, use the corral method. Place t-posts every 10 feet with two layers of polypropylene twine wrapped around the outside edges and criss-crossed between the t-posts at 18" and 36" above the ground.
Growing
Pinching: If you'd like a stockier plant with more blooms (who doesn't want this?), pinch off the top of your plant right above a set of leaves when plants have 5 - 6 sets of leaves.
Fertilizing: Check out our "Fertilizing...or Not" section on our Farm Practices page to learn how we feed our soil microbes which in turn "feed" our dahlias.
Watering: Once sprouted, water deeply 2 times per week, possibly more in hot dry climates. You'll know it's time to water if you stick your finger down into the soil and the soil feels dry.
Weeding: Dahlias have shallow roots and are particularly susceptible to herbicides, so hand weed only. Use mulch to cut down on weeding, cover your bare soil and feed soil microbes.
Pest & Disease Management: Insects such as aphids, thrips and tarnished plant bugs can carry dahlia viruses from infected plants to healthy ones while feeding.
You can make your dahlias less palatable to pests and more disease resistant by following our practices under "Soil Care" and "Pests & Disease."
Harvesting
Harvesting: For more blooms with long strong stems, harvest every 3 days making deep 14 - 18" (or more) cuts right above a set of leaves with floral snips.
If you're growing dahlias to give away or sell tubers, you'll want to be conscientious of limiting the spread of dahlia viruses by sanitizing your snips after harvesting on each plant. Although there are many ways to do this, I carry a plastic caddy with snips in each compartment all soaking in Virkon. After I use snips, I put them back in their caddy space and move to the next snips. By the time I rotate back through, each snip has been soaking in Virkon for at least the 5 minute recommended sanitizing time.
Harvest flowers in the cooler parts of the day (early morning or evening). Strip the leaves and other buds from the stem so there's less to re-hydrate and plunge immediately into clean water for longer lasting blooms.
Move blooms indoors out of direct sunlight as soon as possible and let them re-hydrate for a few hours before arranging them. Add a floral preservative to your water and change your water daily to help preserve your blooms.
Deadheading: Remove spent blooms from your plant to keep it growing and blooming all season long. If you planted your dahlias to enjoy their cut flowers, you don't want to leave spent, open-centered blooms on your plant or they'll be pollinated and your plant will shift its bloom-producing energy into seed-making.
Remember to cut deeply into the plant when deadheading just as you would when harvesting ripe flowers. This encourages branching and more blooms.
Digging & Storing
Unless you live in USDA hardiness zones 8 - 11, you'll want to dig up and store your dahlia tubers if you want to replant them next season.
If you're in zone 7 and below and don't want to go through the trouble of digging and storing your tubers, leave them in the ground to decompose and nourish your soil for next season's dahlias. Just be sure to sign up for our mailing list below to be notified of next season's tuber sale so you can replace them!
Take care that the tubers don't freeze at any point during the digging, washing, dividing and storing process because a frozen tuber is a dead tuber.
Digging: After the first frost, cut the plants back 3 - 4 inches above the ground. If there's no rain in your forecast, wait a week to begin digging tubers, if possible, to allow eyes to swell and make dividing easier.
When ready to dig, carefully loosen the soil 12" out from the plant with a digging fork then gently lift the tuber clump out of the soil. Don't shake the dirt off of it because you could break tuber necks.
Washing: Having dirt on your tubers helps retain moisture so they store better but...it can make seeing eyes difficult when you're dividing your tuber clumps. If you decide to wash the clumps, let them air dry (not overly dry that they start shriveling and never on cement) before dividing and storing. If your soil is sandy-ish, you can also try using compressed air to get excess dirt off your tuber clumps so dividing is easier without having to dry them.
Dividing: If you want to increase the amount of dahlia plants you'll have for next season, you'll want to divide your tuber clumps. Tubers may be divided at this point, or you can wait and do it during the winter or early next spring. To cut down on virus and disease transfer, sanitize shears between each clump. This video demonstrates how to locate the eyes and make cuts accordingly.
Storing: Tubers can be stored in several ways; cardboard boxes, paper bags, plastic bags, plastic wrap or large plastic storage tubs with peat moss or coarse vermiculite.
They store best in a cool, dark, humid place where the temperature stays between 40 and 50 degrees F. Unfinished basements, cold storage areas or corners of heated garages where they're protected from freezing are all good options.
The goal for dahlia storage is to keep them moist enough they don't shrivel and dry enough they don't rot. This depends largely on your climate and storing location. If you live in a dry, arid climate, go for the plastic options to retain moisture. If you live in a really humid environment, you could try the cardboard or paper bag options first to cut down on moisture levels.
Check your tubers often during storage to make adjustments as need--more ventilation for too much moisture and more water (sprinkling) for conditions that are too dry.
The Dahlia Doctor has some great information on the storage of dahlia tubers. You can read it here.
