Planting and Caring for Dahlias
Dahlias are a sought after, gorgeous flowers that come in a variety of shapes, sizes and colors. They are not super difficult to grow and care for, in this article we share some tips and tricks that have helped us grow better dahlias over the years. Not all the tips below will work for everyone, so try some and see if they work for you.
Planting Your Dahlias:
Timing: It’s important to plant your dahlias out after your last frost of the season. You can plant before the last frost, but you do risk your dahlia tuber freezing and rotting. The soil needs to be above freezing levels, and a good rule of thumb is to plant after the last frost to ensure your soil is warm enough.
Soil: Ideal soil for your dahlias is a well draining soil high in organic matter, but most of the time we don’t have ideal soil conditions. If you have heavy clay soil (like we do), add some compost or a cover crop to try to add nutrients back into the soil. It takes years and lots of time and effort to get your soil to great growing conditions, so be patient. You can always get a soil test done for a small fee, we use the University of Minnesota for soil testing.
Light: You’ll want to choose a spot that has full sun. Some shade is OK for your dahlias, but choose a spot that has at least 6 hours of good daylight.
Water (Irrigation): Dahlias need quite a bit of water, so choose a spot that is close to irrigation or easy to water. Watering your dahlias in the morning is best. You can water your dahlias overhead (like a sprinkler) but ideally you are watering your dahlias at the base of the plant to prevent water sitting on the plant.
Planting: Plant your dahlia tubers about 6” deep, if you have heavy clay soil you can plant them a little shallower (around 4”-5” deep). If your dahlia tuber has a sprout, you can plant that sprout facing upward so it grows upward. If the Dahlia tuber does not have a sprout, do not worry. As long as the tuber has an eye it should grow, you can simply plant your tuber in your hole (the sprout will grow upward regardless of how you plant it). DO NOT water your dahlia tubers until you start to see growth above the soil, if you water your dahlias before you see growth your tuber could rot. If it rains before you see growth above the soil, don’t worry. As long as there isn’t torrential downpours for days, your tuber should be just fine. Once you start to see growth above the soil, water your dahlia plants throughout the season.
Caring For Your Dahlias:
Fertilizing: Choose a well balanced fertilizer at the beginning of the growing season higher in nitrogen, this will give the plants food to grow more greenery and get larger. Once you have larger, established plants, switch to a fertilizer that is higher in phosphorus which will promote more blooms. If you notice your dahlia leaves start to yellow and look diseased in the season, try adding some magnesium (Epsom salt). Sometimes your soil is deficient of magnesium which can impact your dahlias, but simply adding Epsom salt during the season will help.
Pinching: When your plants are about 6-12” tall, you can pinch the plants back. Simply cut right above a set of leaves to pinch your dahlias. What this does is encourage your dahlia plants to branch out and create more flowers. If you don’t pinch your plants, they’ll still produce flowers. The stems may be larger and you won’t get as many side shoots that produce flowers. I recommend pinching so you can get as many flowers as possible.
Harvesting: Dahlias are flowers that do great the more you cut! Cut them deep, above a set of leaves and they’ll produce long, strong blooms. Harvest your dahlias early in the morning when it is cool, and place them in cold water. They’ll last 5-7 days once harvested. Harvest them when they are fully open because they do not continue to open once cut. You should check the back of the dahlia to make sure the petals haven’t started to fade. If the back petals are fading, brown, or unhealthy, the bloom will not last as long. They’ll still be beautiful but die quicker once cut.
Plant Care: To promote good airflow, you can remove the bottom leaves of the dahlia plant. This will allow air to flow freely throughout your plants and prevent disease like powdery mildew. Dead head (meaning, remove flowers that are faded) as often as possible to promote more blooms.
