Dahlia Growing & Storage Guide
Our farm specializes in dahlia growing for both cut flowers and tuber production. We are currently growing 35+ varieties.
Dahlias are grown from a tuberous root. They take about 6-8 weeks to start blooming and they are a cut and come again flower. After 4+ months in the ground, a single tuber will multiply into a tuber clump containing on average between 4-20 tubers. In the fall or spring, these tuber clumps can be dug up and divided into single tubers, multiplying your stock for the next season.
Planting - Plant out dahlia tubers in well draining, fertile soil once the danger of frost has passed and the soil temps reach 60 degrees F. Plant each tuber 12-18 inches apart in a location that gets at least 8 hours of sun. Do not water them in when planting to avoid tubers rotting. Start watering once dahlias have sprouted.
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Staking - We recommend staking dahlia plants at a young age to prevent plants and blooms from toppling over. The most common methods are metal or wood posts with 6 inch hortonova netting or twine.
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We use netting with 6" holes. Check out the hortonova netting we use here.
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Pinching - To promote lateral branching and more blooms, pinch back your plants when they are young and have 4-5 sets of leaves. After pinching, plants will take about 4 weeks to bloom.
Watering - Start watering your dahlias when they start sprouting. Dahlias need at least 1" of water per week.
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Fertilizing - Dahlias are heavy feeders. We use a combination of all natural top dress fertilizers and liquid fertilizers.
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Example Feeding schedule -
At pinching time and every 4 weeks, feed an all purpose, nitrogen rich top dress fertilizer
(4-4-4 npk)
Once you cut your first blooms, feed plants with a fertilizer rich in phosphorous and potassium and magnesium to give plants a boost and help the plants uptake all of the nutrients (0-10-10 npk). Feed with liquid flower fertilizer every 2 weeks until about 2 weeks before your first frost.
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Here are our favorites -
Alaska Morbloom Liquid Fertilizer
Harvesting - The best time to harvest dahlias is in the early morning before the sun gets too intense and before it gets too hot. When harvesting, cut the stem at a 45 degree angle and put into clean water. Cut deep, 18”-24”, to promote longer stems. Once cut, keep blooms out of intense heat and sun and if you are not using a cooler, place them in the coolest, darkest room of your house. For longer vase life, change vase water daily and give stems a fresh cut every other day.
Digging & Dividing - When you plant a single tuber, over the course of the growing season it multiplies and creates a tuber clump. Each clump can consist of anywhere from 4-20 + tubers. Each clump can then be dug up in the fall time or even the spring, to divide and re-plant your now multiplied stock. Simply use a pitchfork and dig out about 12 inches from the stalk. Cut stalk down to prevent rotting tubers.
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When dividing, use a sharp pair of scissors to divide your tuber clump. Look for eyes and divide each tuber with at least one eye and a good strong neck.
Storage Over Winter - Once dug up in the fall, you will need to store your tubers in a semi controlled area until planting time in the spring. Ideal conditions are between 40-50 degrees F with humidity levels of about 70-80%. Store as unwashed, whole clumps or wash, divide and store in a medium such as peat moss, vermiculite, or fine pine shavings.
If you would like to overwinter in the ground, simply cut down the main stalk as low as you can and cover with mulch, hay, and/or tarp to withstand freezing temps.
Virus & Disease - Dahlias can be affected by many viruses and diseases that are naturally occurring in nature but can also be spread from poor sanitation practices. We recommend getting familiar with the most common diseases/viruses and what signs and symptoms to look for. Some of the most common are Leafy Gall, Crown Gall, and Dahlia Mosaic Virus. When we see virus or diseased plants or tubers, we discard the whole plant/tuber clump.
An important part of controlling and limiting the spread of diseases and viruses to your dahlia garden and tubers is to sanitize your tools. Use 70% isopropyl alcohol or a 1:10 bleach water solution to sanitize your snips between cuts (we sanitize between each plant and tuber clump.)
Where to purchase - Big box stores often sell Holland grown dahlia tubers that have been riddled with disease and virus, and poorly taken care of, causing poor quality tubers. We recommend purchasing from small farms across the US for the best chance of getting high quality dahlia tubers of known variety.