DAHLIA CARE
Growing dahlias at home is a rewarding way to add color and texture to your
garden from midsummer through fall. Check out the tips below!
Planting
If possible, get your soil tested by your local county extension office 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.
Getting your soil tested for macro and micronutrients and then adding the recommended amendments to bring your soil nutrients into balance will be the biggest difference maker in the growth and health of your dahlias.
Read more about soil testing here.
Where: Pick an area with well-draining soil that gets at least 6 - 8 hours of full sun. If you live in an especially hot climate, dahlias appreciate afternoon shade.
When: Plant in late spring after all danger of frost has passed and the soil has warmed to 55 - 60 degrees.
How: Space dahlias 12 inches apart. Dig a 4 - 5" deep hole and place the tuber horizontally with the eye (sprout) facing up if possible. Cover with soil and place a plant label.
If you have slugs, sprinkle Sluggo around the planting area or the slugs may enjoy your sprouts before you see them.
Watering: A good rule of thumb is to avoid letting tubers sit in either soggy soil (which can cause tubers to rot before they establish roots to take in water) or bone-dry soil.
Waiting to water until you see growth is a common approach and works well in humid climates with occasional rain. In very dry regions though, you’ll want to lightly moisten the soil now and then so it doesn’t dry out completely.
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 placed at planting.
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: Pinch off the top of your plant right above a set of leaves when plants have 5 - 6 sets of leaves. This will give you a stockier plant with more blooms.
Fertilizing: Dahlias are heavy feeders—it takes a lot of nutrients to produce those big beautiful blooms!
Check out our "Natural Fertilizing" section on our Farm Practices page to learn how we feed our soil microbes which in turn "feed" our dahlias.
If you prefer a more conventional approach, there are plenty flower fertilizers available but again, I recommend a soil test first to determine your soil's specific needs so you're not overdoing it on nutrients that can build up in the soil.
Generally speaking, a balanced fertilizer (close-to-equal NPK numbers) promotes strong early growth.
When you start to see buds forming, switch to a fertilizer where nitrogen (N) is lower than phosphorus (P) and potassium (K). This encourages flowering over leafy growth (the opposite will be true if you don't switch to a lower nitrogen fertilizer once you see buds forming).
Fertilize every 4 - 6 weeks (or as directed on your fertilizer). Stop fertilizing dahlias about one month before your first frost date so as not to interfere with tuber production.
This article from the National Capital Dahlia website has some super specific fertilization tips if you want a deep dive.
Watering: Watering needs vary widely based on climate and soil type.
Generally speaking, once your dahlias have sprouted, plan to water deeply 2–3 times per week throughout the season—possibly more often in hot, dry conditions.
The best way to dial in your watering is with a quick soil check. On a day you’d normally water, stick your finger all the way into the soil. If the soil feels soaked from the last watering, space your watering days farther apart. If the soil feels bone dry, you’ll want to water more frequently.
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. They can also stress your plants and impact your blooms.
You can make your dahlias less palatable to pests and more disease resistant by following our practices under "Soil Care" and "Pests, Disease & BRIX."
If you prefer a more traditional approach, a preventative spray of insecticidal soap and neem oil every two weeks can help keep pests at bay. If you notice damage on leaves or blooms, increase the spray to once a week until the problem is under control.
Although both products are natural, they can still harm beneficial insects and may burn leaves if applied in hot sun. For best results, spray in the early morning or evening (when beneficials are less active), and avoid applying during the heat of the day.
Harvesting
Harvesting: For more blooms with long strong stems, harvest every 3 days making deep 18" (or more) cuts right above a set of leaves with floral snips.
If you're growing dahlias to sell tubers, you'll want to be conscientious of limiting the spread of dahlia viruses and gall by sanitizing your snips after harvesting on each plant.
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.
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 subscribe to our newsletter 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 your dahlias have been in the ground for at least 120 days, you're free to dig them up! You can wait until after the first frost but you certainly don't have to. When you're ready to start digging, start by cutting the plants back to 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: Wash your tuber clumps before dividing and storing. If your soil is sandy, you could try using compressed air to get excess dirt off your tuber clumps instead of water so you can skip the drying process.
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 right after you've washed them, 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.
Drying: Once they've been washed and divided, let them air dry and your recent cuts heal over until dry to the touch (not overly dry that they start shriveling and never on cement).
Storing: Tubers can be stored in many ways; cardboard boxes, paper bags, plastic bags, plastic wrap or large plastic storage tubs with coarse vermiculite, peat moss or wood shavings. I would suggest asking other dahlias growers in your same area (you can find them on FB) how they store their tubers to get an idea of what works best in your climate.
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 garages where they're protected from freezing are all good options.
The goal for dahlia tuber storage is to help them retain their moisture so they don't shrivel, while keeping them dry so they don't rot. How to achieve this balance depends largely on your climate and storing location.
If you live in a dry, arid climate, go for the plastic options to help retain moisture. If you live in a really humid environment, you could try the cardboard and wood shavings 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.
