Growers FAQ

Don’t go for suppliers who carry imported dahlia tubers including importers and big box stores. They very often carry disease, are poor quality, and can be mislabeled.

Dahlia growers can purchase dahlias in the fall or spring but be sure that the seller ships them in spring. Avoid imported tubers and tubers from big box stores; they often have diseased, poor quality, and often mislabeled. Instead, purchase from growers and suppliers in the U.S.

Our sale starts March 1 of each year, so mark it on your calendar to take advantage of our season sale! Shipping begins in April, we ship to all 50 states.

We would love to help answer this, check DahliaSearch, the online dahlia database.

We recommend doing a one-time pinch of the central stem when you see 4-5 leaf sets, or when your plant is about 12″ tall; removing the tip off the central stem, which enables your plant to branch out laterally providing more foliage and more blooms. If you don’t pinch your dahlia plant, you will end up with a single stalk with blooms at the very top.

Wait for the first bloom at the top, then cut the stem 15″ down which acts like a pinch, enabling the plant to spread out.

It depends on your growing zone, but generally in early spring after your last frost. The ground temperature should be at least 50f or warmer.

4-6″ deep no matter if you plant directly in the ground, in pots, or in clumps. It is a good time fertilize with Osmokote for the hole you make in for your tuber. Osmokote is a granular, slow release fertilizer that gives your dahlia tubers a good start and leads to a healthy plant. Give one heaping table spoon of blood meal for each plant, scratch it into the surface with a plastic fork (or something like it).

Never. Soak. Tubers. Even if your tubers seem dry and shriveled up, they will get enough moisture from the soil.

We recommend using straw over shredded bark. Moist, shredded bark attracts earwigs which can crawl up your plant and chew your leaves and blooms. Straw provides some earwig protection for newly planted sprouts, and some protection from the heat.

We follow what Swan Island dahlias recommends, which is two parts top soil, mixed with one part potting soil. You can add compost or bagged cow manurer (not fresh cow manurer). Mix about a cup in your container.

Extreme high heat can slow down growth of your dahlias. They can become wilted. Some of the new sprouts can burn at the soil line. We recommend using shade cloths, which can be found on Amazon. They come in different sizes. Look for a 40-60% shade cloth with grommet edges. Use it as a canopy over your plants. Your plants will love growing in the filtered sunlight without taking all the heat. The cloths are a lightweight shade fabric that allow breeze and water to pass through it, without the harmful effects of the sun.

No. Wait until the sprout is 3″ above the ground to water, then gradually increase water as stalk grows taller.

This is caused by tarnish plant bugs. When you see them, pick them off and drop them in a bucket of soapy water. We also recommend using organza bags and tying them over the bugs. The blooms can open inside the bags without receiving insect damage. We use the 10×14″ organza bags for the largest blooms, then folder them in half inside for the small and medium sized blooms.

Use Sluggo Plus, available at Swan Island Dahlias.

The first 8 weeks of a plant’s development, the tuber concentrates on creating a root system to support the leaves, followed by blooms. It can be about 12 weeks before you see blooms. Some of the largest dahlias bloom late in the season (August, September, October).

Fertilizer is very important from the very beginning. You want to start with the Osmokote at planting time, along with a heaping tablespoon of blood meal per plant, scratching it into the surface with a plastic fork or similar. Once the plant is 12″ high, start giving them Miracle Grow Bloom Booster up until July 1; feeding them once every 3 weeks. Then, switch to Alaska More Bloom (0 – 10 – 10); we give that to them once a week. We stop fertilizing a month before harvesting the tubers.

Tubers need at least 6 hours of sun. If they are planted in a shady location, they won’t do as well, as they will be reaching for light and become very leggy; they need sun.

It’s an easy fix. It’s caused by lack of air circulation, warm temperatures, and moisture. You can spray it with Lysol Disinfectant Spray, let them dry to touch, or you can use a Lysol Disinfectant Wipe to wipe them off. Vent the top of your container for a few days and make sure they’re in a cool, dark place.

If you are in a growing zone with freezing temperatures and/or snow, you will need to store them inside over winter. We usually harvest ours in late fall, between October 15 and 30 is when we dig them up, rinse them with a hose on jet spray, let them dry out for 24 hours.

You can put them in a plastic container with a top. You need a packing medium to layer your tubers in. You can use peat moss, vermiculite, hamster shavings bedding, or white pine needles. Start by putting packing medium in the bottom of the container, then a layer of tuber clumps, then more packing medium, and keep repeating this. You should finish with your packing medium on top.

All dahlia tubers need to be completely covered. Vent the top for a week (keep the top on your container half open, letting some of the moisture escape, then close the top). The container should be in a cool, dark room. The ideal temperature is 45f.

Check on your dahlias every 3 weeks until you take them out to start waking them up 4-6 weeks before your last frost. Check for moldy, shriveled, or rotten tubers.