Tips for getting more blooms from your dahlias
Dahlias are a beautiful addition to summer gardens. Grown from tuberous roots planted in the spring, dahlia blooms come in a near endless array of colors and forms. From spiky-petaled cactus-types to round and tight pom-pom dahlias, this tender plant brings some serious bloom power to the garden.
Planting dahlias each spring is fairly easy, as long as you remember to plant the tubers just a few inches beneath the soil, but caring for them throughout the summer months can be a bit more challenging, if you don’t keep a few things in mind. Today, I’d like to share some great tips for growing healthy and productive dahlia plants from now until the first frost of autumn.
Tip 1: Keep the plants upright. Dahlia blooms are easily spoiled if the plants are left to flop on the ground. Use a 1-inch-by-1-inch hardwood stake to keep the stems straight and upright. You’ll need some strong jute twine to fasten the plant’s branches to the stake. Since dahlia plants are fairly fast growers, check the plants once a week to see if they need to be tied higher up on the stems. For large dahlia varieties with a lot of branches, consider using a heavy wire tomato cage to keep the plants upright. If you go this route, you’ll need to insert the tomato cage over the plant when it’s just a few inches tall. If you wait too long to put the cage on, you’ll have to wrestle the plant to corral it inside.
Tip 2: Deadhead. Dahlia blooms are beautiful, but they don’t last forever. As soon as the flower has faded, use a sharp pair of pruners to trim the flower stem off just above the point where it emerges from the main stem. Don’t leave a stump behind when deadheading. Removing spent flowers regularly encourages the production of more blooms and eliminates seed production, a process that saps a lot of energy from the plants and reduces future blooms.
Tip 3: Fertilize. I fertilize my dahlias with a liquid organic fertilizer every two weeks, at the same time I feed my container plantings. Liquid fertilizers are absorbed by both the roots and the leaves, so don’t hesitate to apply it to the foliage, too, as you saturate the soil. A liquid organic fertilizer that’s slightly higher in phosphorous promotes good flower production and keeps the plants from developing weak, spindly stems.
Tip 4: Watch for fungal diseases. While dahlias are fairly trouble-free, fungal issues do sometimes strike. Bud blast will cause the flower buds to flop over and rot before they open, and leaf spot foliar diseases can easily mar the foliage. To keep these issues at bay, give your dahlia plants plenty of room to grow and be sure to keep other plants from crowding in around them. Trim nearby foliage to increase air circulation around the plants. If you happen to spot any diseased foliage on your dahlias, promptly trim it off and discard it in the trash.
Tip 5: Irrigate. Larger species of dahlias can grow quite tall, and they get thirsty as they grow. Be sure to keep your dahlia plants well watered, especially during times of drought. Mulch the plants with a few inches of shredded leaves, leaf mold or compost to help retain soil moisture. When you water the plants, apply a deep, soaking amount of water once a week, rather than a light spritz of water every day or two. Deep irrigation encourages deep root systems that are better able to access their own moisture and nutrients.
With these tips, your dahlias are sure to produce oodles of gorgeous blooms for months to come!
Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio with Doug Oster. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden,” “Good Bug, Bad Bug,” and her newest title, “Container Gardening Complete.” Her website is jessicawalliser.com. Send your gardening or landscaping questions to [email protected] or The Good Earth, 622 Cabin Hill Drive, Greensburg, PA 15601.