Dahlia Growing Guide
Plant Dahlia's when soil has warmed to 60°F., and when the danger of further frost has passed. Dahlias require well drained, rich, organic soil with no less than 6 hours of sunlight, 10 hours is optimum. Loosen 8-12” of soil to create a hole and sprinkle a dusting of bone meal into each hole. Plant the tuber horizontally with eye facing upward, or keeping the stem(s) or sprouts upright. The top of the tubers, where the sprout emerge, should be positioned 3-4" below the soil surface when the hole is filled in. Fill in around the tuber, firmly pressing down the soil. Plant dahlias 12-15” apart. Once the dahlia emerges, add compost to level the hole with surrounding bed and add all-purpose granular fertilizer to the planting area and mix well.
Keep in mind underground critters love the dahlia diet! We mix crushed oyster shells around our tubers to help deter the nibbles or theft of our beauties. Earwigs and slugs also have a hearty appetite for dahlia stems and leaves! We sprinkle the soil beneath our plants with Slugo Plus pellets. Our field is visited by deer, moose and marmots who also like to take nibble along their trek. We use granular Repels All around the boundary lines of our rows.
Other Tid-bits:
To get a jump start to the flowering season, you can plant the tubers in pots indoors 6-8 weeks before transplanting into the garden. Once the shoots appear, provide light with indoor grow lights or south-facing window,. Offer sprinkle of water if you see developing roots.
When the plants are 12" tall, or have at least three sets of nodes, pinch off the top of the main stem. This will fill out the plant with even more vertical stem, offering a fuller plant, more blooms and more wind resistance.
A common mistake when growing dahlias is overwatering tubers you have just planted. Too much water at this early stage can lead to rot. Wait to water until dahlia sprouts are a few inches tall with growing leaves. Do not overwater young plants. If you live in an area with heavy rainy springs, you may want to consider covered hoop rows until your dahlias can drink up the water om their own. Tubers without roots do not need watered.
Routine watering depends on your climate. Water deeply 2 - 3 times a week, allowing the top 1" of soil to dry out in between waterings. Our climate is not humid in summer, so we dont have challenges with powdery mildew. Plant your tuber 12 - 15 “ to allow for airflow and allow your plant leaves to dry before night time temps so water doesn’t sit on leaves.
Dahlia plants will benefit from foliar, water-soluble fertilizer every 2 - 3 weeks from July to September. Stop fertilizing in lane September to help tubers prepare for dormancy.
Deadheading is important to promote new blooms. If you don't do it, the plant will stop flowering and focus on making seeds. Use clean, sharp garden scissors to cut off wilted dahlia flowers just above where the flower stem meets a leaf.
Dahlia tubers can be lifted for winter storage at any time, as long as the plant had been growing for over 120 days.
Overwintering:
In fall, after the first frost has blackened the foliage, cut off all but 2 to 4 inches of top growth, and carefully dig tubers without damaging them. Allow to dry for a few days in a frost-free location, out of direct sunlight. Once dried, remove any excess soil, leaving 1 to 2 inches of stem. Store each clump of tubers in a ventilated bin or basket. Fill the box with peat moss, clean wood shavings or vermiculite and place it in a cool, dry location. Saran wrapping individual tubers is also a great overwintering option, recommended by American Dahlia Society.
Optimal temperature for overwintering is 44 - 50°F. Don't allow your tubers to freeze.. If temperature is too warm however, they may start to sprout in storage.
Maintaining proper humidity is crucial. If stored wet, tubers will mold and possibly rot. If they are stored too dry, they will shrivel up and may die. A little shriveling is perfectly normal and won't affect the viability of the tubers.
Check tubers periodically through winter for rotting and drying out. If the tubers appear shriveled, mist them lightly with water. If any start to rot, trim the rotted portion of the clump so it won't spread. The tubers are fragile, so be careful when handling them.
When warm weather arrives, you can plant the overwintered tubers and begin the growing cycle again.
Happy Gardening!
