How to Grow Dahlias | Beautiful Flowers for the Garden

Here are some easy tips on how to plant dahlia tubers and how to grow dahlias from seeds in the garden this spring.

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Are you looking for a beautiful flower to grow in your spring garden? Here are some tips on how to grow dahlias from both tubers and seeds.

With their tall stems and large blooms, dahlias are sure to make a bold statement in the garden. They are a good replacement for roses in areas where it’s hard to grow roses.

There are more than 100 varieties of dahlias to grow, including the cactus dahlias. There are plenty of colors to choose from if you are trying to get a certain look or aesthetic for your garden or home.

Dahlias often bloom from midsummer until fall, providing color over a long gardening season. They come in a variety of colors, including vibrant reds, pinks, oranges, and bicolors.

Growing bunches of dahlia plants can be a great way to fill in space and make your garden a memorable place for years to come.

Interesting varieties like the cactus dahlia “Nuit d’été” (“Summer Night”) are perfect for adding both unique color and petal shapes to a garden. For a real showstopper, check out the dinner plate dahlias for extraordinary, large blooms.

In addition to being quite hardy, dahlias can be a low maintenance plant to grow—with some exceptions.

Here are some tips for how to grow dahlias from tubers and how to grow dahlias from seeds.

How to Grow Dahlias from Tubers

Starting dahlia plants from tubers is one of the most popular ways to grow dahlias. You can often order dahlia tubers from online catalogs or mail order catalogs or buy them from a garden center.

Start with fresh dahlia tubers. When choosing dahlia tubers to purchase or plant, it can be a good idea to avoid tubers that look dried out or withered.

Soil temperature is an important factor when it comes to growing dahlias from tubers. Make sure the soil temperature is consistently at around 60 degrees Fahrenheit before planting the dahlia tubers. Dahlias generally do not grow in cold soil, and they are sensitive to frost.

Provide dahlia tubers with at least 6 to 8 hours of full sun each day. (Dahlias growing in hot climates may benefit from afternoon shade, however.)

Choose a spot with fertile, well-drained soil and located in full sun to plant dahlia tubers. Dig a hole that is about 6 inches deep for each tuber, and space each hole 12 to 18 inches apart (use wider spacing for larger varieties).

Use a garden fork to loosen the soil to about 12 inches deep in the spot where you want to plant the tuber. Add a granular, all-purpose fertilizer or compost to the soil and mix in with the soil before planting the tubers.

Place a tuber in each hole, with the stem or sprout “eye” side facing upwards. Cover with about 1 to 2 inches of rich, loose soil, but don’t bury the tubers too deeply. The dahlia tubers should sprout in about 4 weeks, but sometimes it takes longer.

In cool wet climates, you may not need to water the tubers until they sprout. But in hot dry climates or places experiencing drought, it can be a good idea to sprinkle a small amount of water over the areas where the tubers are planted, to help keep the soil moist.

Do not overwater the dahlias, as too much water can cause the tubers to rot.

Once the dahlia plants appear above ground, water regularly to keep them happy. Fertilize the plants throughout the season to encourage them to grow and bloom. A low nitrogen, 5-10-10 fertilizer may be a good choice for using to feed dahlia plants. A general rule of thumb is to fertilize dahlias once a month from the time the plants appear until early fall.

Potential dahlia diseases include powdery mildew, botrytis blight (grey mold), and rot. Avoid overwatering plants and prune regularly to encourage air circulation. Remove debris from around plants.

Dahlia pests include aphids, earwigs, thrips, and slugs and snails. Spraying regularly with organic insect spray or insecticidal soap may help to control certain pests. Sluggo may help to control slugs and snails.

Keep an eye out for animals who may decide that your dahlia tubers would make a great meal. Voles and other rodents will sometimes go after dahlias and tubers. Avoid placing mulch around dahlia plants, as this can be a breeding ground for earwigs and other dahlia pests.

How to Grow Dahlias from Seeds

Growing dahlias from seed can be cheaper than growing dahlias from tubers, and it is a fun experiment to try.

Dahlia seeds can be tricky to start. Starting dahlia seeds using the paper towel method is one way to encourage dahlia seeds to germinate.

To try this method, sprinkle dahlia seeds onto a paper towel, cover them with another paper towel, and mist with water to wet the towels.

Carefully place the seeds in a large sealable bag or container, loosely seal, and place the bag in a warm, sunny place until the seeds start to germinate.

As the seeds start to germinate, prepare a home for them by filling the individual cells of a seed starting tray with sterile seed starting mix. Use a dowel or pencil to make small holes for planting tiny, sprouted seeds.

Once the dahlia seeds germinate, prick the tiny plants from the paper towels and gently plant them in the seed starting cells. Leave the green parts of the plant above the soil line.

Place the seed starting tray under a grow light to encourage the seedlings to grow. Once the seedlings are a about 2 to 3 inches tall, transfer them to bigger pots.

Continue potting up plants as needed to provide dahlia plants room to grow while you wait for the weather to warm up outside.

You can also start dahlia seeds directly in a tray of cells filled seed starting mix. Place the tray under a grow light to help encourage growth. A seed heating mix may be placed under the tray to help encourage germination.

Start dahlia seeds indoors 6 to 8 weeks before the last frost date in your area, or direct sow dahlia seeds after the danger of frost has passed. Dahlias are sensitive to cold, and prefer warm soil (60 degrees Fahrenheit or above) and warm ambient temperatures.

It can take 100 to 120 days for dahlias to produce blooms when grown from seed, so allow plenty of time for your plants to grow during the season. Depending on where and how you grow, dahlia blooms may start to appear between mid-July and August.

By the end of the season, dahlias grown from seed may produce tubers that you can dig up to store indoors during winter. These dahlia tubers can be planted in the garden the following spring.

Popular Dahlia Varieties to Grow

Here are some dahlia varieties that can be productive and/or relatively easy to grow.

The best time to order dahlia tubers or dahlia seeds is late winter, when new seed catalogs are published and shipped. Dahlias are popular flowers to grow, and tubers and seeds can sell out quickly.

Diva

Diva is a tall dahlia variety that has purple blossoms. The plants are often productive from midsummer to frost. Grow this plant at the back of a garden (it can grow quite tall) for luxurious blooms during summer.

Meagan Dean

Meagan Dean dahlias produce a light lavender bloom that is pretty for flower arrangements and bouquets.

Unwin’s Mix

This cheerful mix of dahlias can be grown from seed. A mixture of colorful single and double blooms, Unwin’s Mix dahlias are a great choice for borders and containers.

More Tips on Growing Dahlias

  • Dahlias are members of the Asteraceae family, which also includes asters, chrysanthemums, daisies, sunflowers, and zinnias.
  • Dahlias come in all shapes and sizes, and some varieties are more prolific than others. Some dahlia varieties may be prone to powdery mildew.
  • It can be a good idea to check with your local extension service or master gardeners club to find out about dahlia varieties that may be good to grow in your area. Many dahlia varieties can be grown in zones 6 to 11. Dahlias may be grown as perennials in zone 8 and above.
  • Border dahlias can be a good variety to grow in small spaces and containers. Prune plants regularly and keep them watered and fertilized. Mixing a small amount of compost into the soil of your container grown plants may help the dahlias to grow. Use a good quality soil mix that is made for growing plants in pots and containers.
  • For a bushier dahlia plant, cut the central stem just above the third or fourth set of true leaves once the plant reaches 12 inches tall. This helps to produce a stocky plant with more branches, and sometimes more blooms.
  • Full sized dahlia plants can reach 3 to 4 feet tall or more, and the plants may benefit from being staked or caged for support.
  • As dahlia plants grow, prune the lower branches and leaves from the plant to encourage air circulation. Remove old flowers from the plants and clip regularly to encourage new blooms.
  • Slugs and snails love dahlia plants and can destroy plants quickly. Earwigs are another common dahlia pest. Use protective barriers or other forms of pest control to help prevent slugs, snails, and other bugs from destroying your plants. Keep the area around your dahlias free from leaves and other garden debris to give garden pests fewer places to hide.
  • Dahlias typically don’t survive winter in cold places, and are grown as annuals, instead. To grow dahlias from year to year, you can try digging up the tubers and storing them indoors over winter, to be replanted outside in the garden the following spring.

This post was all about how to grow dahlias.

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Credits
  • Photo by Tiffany Rebecca / Unsplash
  • Photos are for illustrative purposes only.

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