How to Care For Your Dahlias After Planting: Tips for Pruning, Watering, Fertilizing & Pest Management
We’ve said it before, and we’ll say it again: dahlias are one of our favorite flowers here at Sweet Earth. There are endless varieties of dahlias, available in a multitude of styles, sizes, and colors.
Curious about the basics of dahlias? Check out our Flower Focus post to learn more about these flowers.
We’ve shared on the blog before some of our favorite varieties to design with, along with how to pot up dahlia tubers, but today we want to dive into how to best care for your dahlias after planting. We’re going to cover pinching, watering, fertilizing, and pest management.
You may also be interested in our YouTube video all about dahlia TLC:
Watering
Caitlin’s Joy Dahlia
After planting our dahlia tubers, we wait until after the first green shoot pokes through the ground and the plant has its first set of leaves before watering. Watering before shoots are visible can lead to rot.
From that point forward, dahlias need deep watering at least 3 times per week. They are deep-rooted and setting an irrigation schedule for 30 minutes to 1 hour at least 3 times per week is ideal for ensuring water gets down to the roots. Because of this, drip lines or soaker hoses are the best option; hand watering is not efficient or effective. Drip irrigation is also ideal because it keeps the foliage dry. Overhead watering can promote fungal issues and spotting on leaves and blooms. Of course, the watering schedule should be adjusted for soil type and rainfall.
Pinching & Pruning
Myrthe Dahlia
After plants reach about 1 foot in height, I give them a hard pinch by snipping the growing center down to the 3rd or 4th set of leaves; this prevents getting a thick center stem (which is not ideal for bouquets) and encourages more branching. More branching means more flower production.
We also strip the bottom leaves of the dahlia plants. Doing so improves air flow and mitigates fungal issues. It also helps with pest pressure, especially slugs, earwigs and other pests that hide in the soil at the base of the plant. It also gives us a clear line of sight for when we apply soil drenches.
Staking
Since dahlia plants can get very tall with heavy blooms, it is important to stake them. I have tried several methods and because I grow a lot of dahlias (about 800-900 plants), what works the best for me and is most efficient is placing stakes about 5 ft apart along the edge of either side of the bed and then corralling the plants with twine. As the plants grow taller you may need to add another layer of twine. For those who are growing a small patch of dahlias, I recommend placing a stake in the hole when planting the tuber, giving each plant a stake.
Chat Noir Dahlia
Mondriaan Dahlia
Fertilizing
Dahlias are heavy feaders, meaning they require and pull a heavy nutrient load from the soil. Soil microbes are tiny, yet incredibly important organisms that play a vital role in the health and fertility of your garden. These microscopic life forms, including bacteria, fungi, protozoa, and nematodes, contribute significantly to nutrient cycling, soil structure improvement, and overall plant growth.
Golden Scepter Dahlia
Like all living organisms, soil microbes require a source of energy to carry out their functions effectively. Sugar and carbohydrates serve as the primary energy sources for these microorganisms. By providing a steady source of sugar through molasses, you can help support and boost the activities of these beneficial microorganisms, ultimately leading to healthier soil and more productive plants.
I fertilize my dahlias regularly. Once a month I give them a soil drench of molasses and Neptunes’ Fish & Seaweed (affiliate link). During the height of the blooming season and when they seem to be under stress, I also give them a foliar spray of the molasses and fish/seaweed fertilizer.
Pest Management
The major pests I have encountered growing dahlias are thrips, Japanese beetles, earwigs, slugs, and grasshoppers; aphids can also be an issue. My first line of defense against pests is a focus on soil health. As noted above in the section about fertilizing, that entails feeding the soil microbes and ensuring that the nutrients in the soil are well-balanced. My second line of defense is incorporating herbs, such as basil and parsley to help control/repel pests. Lastly, I turn to organic pesticide options such as Sluggo+ and Diatomaceous Earth (affiliate links).
Danique Dahlia
Whether you’re brand new to dahlias, or just wanting to improve your current crop, I hope you found this blog post helpful. Take a look below for a few more resources we’ve put together on growing and maintaining dahlias.
Check out this blog post about how we grow our dahlias here at Sweet Earth Co.
This blog post gives you tips about extending the vase life of your dahlias
Watch this YouTube video showing you how we divide dahlia tubers
Curious why we have so many dahlia plants? In addition to using them in designs, we have a CSA share featuring dahlias each fall. Take a look and claim your share (or get on the waitlist if the spots are sold out)!
Get on our newsletter below to be the first to hear about our annual dahlia tuber sale each spring (and get lots more garden education delivered right to your inbox)
