Dahlia Growing 101

Choose a full sun area with 6-8+ hours of direct sunlight, sheltered from high winds, and well-draining, fertile soil.

Also, dahlia tubers/plants are best when kept out of a low spot, where water may pool during an unexpected weather event.

Dahlia Tubers can be planted after all threat of frost has passed. Typically from Mid-April until Early June, depending on your location and your climate. Dahlia's prefer a soil temperature of 60°F.

Visit The Farmer's Almanac to check your last frost date by zip code.

YES! Dahlias can be planted in 1-2 gallon pots, all the way up to a 10 gallon pot per plant. Containers must have good drainage!

In 2024, we chose to grow all of our dahlias in 7 gallon grow bags, 1 tuber per bag. For more in-depth learning about our process, visit our instagram post: All About Grow Bags.

Dahlias grow best in loamy, well-draining, rich soil with a pH level of 6.5. to 7.

For heavy clay or sandy soil, amend the area with organic leaf compost, worm castings, or other aged, organic material. Planting a cover crop in the "off or pre-season" will also help break up the soil, and add more organic matter and beneficial microbes into the soil.

We highly recommend a soil test to truly pinpoint nutrient deficiencies and ensure you're getting the most out of your garden. Check with your local extension office or university for available options.

First, ensure your soil is gently moistened. When squeezed, the soil should stick together but not drip any water.

Next, dig a hole 6" deep and lay the dahlia tuber horizontally. If you can see the bud or sprout on the dahlia, plant it facing upwards. If not, do not fret, the dahlia sprout will grow upright on its own.

*Optional Step* Add a small sprinkle of Mykos and worm castings next to the tuber. This gives a little nutrient boost to the dahlia while the forming roots.

Lastly, cover the hole and lightly press soil. Be sure to add in a plant tag, stake or marker during this step too!

IMPORTANT NOTE: Do not fully water again until the first sprout appears, as too much water without roots, will lead to rot.

Fertilizer largely depends on your soil.

As a general rule of thumb, apply a balanced fertilizer early in the season (10-10-10), and taper to a lower-nitrogen product once blooms start forming. Too much nitrogen mid-season can lead to more leaf growth and less blooms.

Newly planted tubers should not be watered much (if at all) until they've sprouted. If your soil becomes very dry, water gently. Too much water without root development, and your tuber will rot.

Overhead or drip, dahlias need deep water to reach their roots, but not stay soggy. Avoid consistent overwatering, which leads to tuber rot. Frequency per week depends on your zone and weather. Our normal in Zone 5a is every other day for temps between 70-80°F.

Dahlias need support, as many reach heights between 4 to 6 feet, and even up to 8+ feet!

How you stake is personal preference. We like using T-posts (inserted at planting time) with bailing twine, wrapping every 18 inches to support the dahlia as it grows.

Other options include bamboo rods, green garden stakes, cages, or wooden grade stakes. I would still highly recommend using bailing twine over other strings or yarn however, because of its strength.

Dahlias take an average of 120 days to fully mature and produce tubers. Tuber production heavily varies with each variety.

"Pinching" is the action of cutting off the main growth stem of a developing sprout to increase yield. For dahlias, pinching is best done when the plant has grown at least 4 sets of leaves, and is 12 to 16 inches tall. For pompom varieties, pinch when 5 leaf sets have developed.

Using a set of sanitized snips (or your fingers) break off the center stem right above the fourth leaf set. This will signal the dahlia to push lateral growth between each remaining leaf set, gifting you two to four times the blooms. Pinching also helps keep stems manageable size for bouquet use.

Please note, pinching plants will set the development time back a few weeks. We see this a minor trade for a large, vigorous, and healthy dahlia plant.

YES! One of the best perks of growing dahlias is their "cut and come again" nature. The more you harvest stems and trim dead heads (spent blooms), the happier they become... putting extra energy into tuber production, and encouraging a bounty blooms.

Pests are area and zone dependent.

The majority of dahlia growers battle insects like aphids, thrips, spider mites, grasshoppers, and Japanese beetles (which thankfully haven't made it to our area yet). Arbico Organics has a variety of products and information as well as beneficial insects for purchase. We LOVE adding ladybugs, lacewings, beneficial nematodes, and assasin bugs to our garden each season.

As far as critters go - your typical rabbit, mice and vole can cause damage to tubers. Deer also love munching on dahlia leaves. Control of these mammals come at individual discretion.

To combat both mammal and insect pressure, consider companion planting with alliums, marigolds, and other unpleasant tasting plants. You can also experiment with "trap crops" which attract insects away from your dahlias.

Another newer discovery is the study of BRIX levels (sugar levels) in plants. Listen to The No-Till Flowers Podcast episode here: The Magical Brix Number that Stops Pests with Dr. Tom Dykstra

Just like humans, dahlias are susceptible to virus. Once sick however, the virus attaches to the plant tissue and remains in the dahlia causing vein clearing, stunted growth, yellow necrotic spots, and discoloration. Currently, there is no cure.

Virus is transported through piercing or sucking mouthparts of insects, and transferred via unsanitized snips during harvest and tuber division. Think plant juices coming in contact with other plant juices. Virus is not transported through soil.

The virus issue is not just for dahlias, thousands of other plants also carry the same viruses that affects dahlias. Yes, virus can come from an aphid on another plant and spread it to your dahlia.

The American Dahlia Society has spent thousands of dollars on trying to understand virus, specifically Dahlia Mosaic Virus. Their recent findings concluded 87% of dahlias sampled (even healthy looking, vigorous plants) had at least one virus.

If you're interested in testing your garden, at-home kits can be purchased through Agdia, but note they are costly.

Here's our take. We live in an always moving, growing, and ever evolving climate. Your plant can test negative, and be bitten by an infected aphid the next day. Maintaining perfectly clean stock is challenging, expensive, and nearly impossible given all of the current data available. However, that doesn't give us a free pass to not care.

At Golden Hour Gardens, we follow ADS guidelines by culling suspicious looking plants and sanitizing snips in a 10% bleach solution for two full minutes between plants when trimming, harvesting blooms, and dividing tubers. We also minimize pest pressure by releasing beneficial insects multiple times throughout the season and applying organic pest control solutions when needed.

Our farm is inspected by the Montana Department of Agriculture every growing season, and passes with flying colors. We're committed to do our part in maintaining healthy plants, while being realistic about current virus statistics and solutions.

Fear does not belong in the garden, so regardless of viral chance, we will keep growing and sharing these beautiful blooms for future generations.

Yes, dahlias can contract diseases too. You may have heard of leafy or crown gall. Both are bacterial diseases that are transferred via soil, plant material, or tools. They are truly terrible, and can remain in the soil for years.

If you're looking to avoid gall contamination, stay away from big box stores, and dutch import tubers from larger online sources. Harvest methods, quality control slips, and disease issues are more common when growing on a massive scale.

We LOVE supporting SMALL FARMS + other family run flower businesses. Every single new variety we purchase is directly benefitting another hardworking, farming family. Choices can become overwhelming when shopping small, so we use word of mouth and the Dahlia Addicts Supplier List to help direct our search.

Shopping small is a rewarding in both plant health + ethics.