How to Grow and Care for Dahlias

With so many varieties, you're sure to find a dahlia you'll love growing in your garden!

Choose dahlias that will grow well in the space you have available for them.
Use Miracle-Gro Organic™ Raised Bed & Garden Soil to plant dahlias in in-ground gardens or Miracle-Gro Organic™ Outdoor Potting Mix for outdoor containers.
Plant dahlias in full sun in the spring.
Place stakes next to dahlia tubers at the time of planting or when the plants are small.
Water dahlias once they begin to grow, keeping the soil about as moist as a wrung-out sponge.
A month after planting, feed dahlias with Miracle-Gro Organic™ All Purpose Plant Food to replenish nutrients in the soil.
Deadhead dahlias to encourage more blooms.
Dig up dahlia tubers after the first frost of the year and divide them in the spring before planting.

Dahlia blooms come in all sizes and many colors. They can be as large as a dinner plate or as small as a golf ball. There are single flowers with one row of petals and a big center, double flowers with lots of petals in multiple rows, or even pom-pom shaped dahlia flowers. You'll find them in shades of pink, purple, red, yellow, orange, and white—some are even multi-colored. In other words, there are many different varieties! Dahlias are beautiful as cut flowers and last for several days in a vase, and you'll often see them included in wedding bouquets.

It's no surprise, then, that there are dahlia societies and clubs, dahlia shows, and dahlia collectors. Start growing dahlias and you might find yourself swept up in the urge to find and nurture hard-to-find varieties. No two look just alike and they're all gorgeous, so who could blame you?

How to Choose Dahlias

The main thing to consider when choosing dahlias is the space you have available to grow them. Some dahlias can grow to heights of 5 or 6 feet, while others are much shorter and will live happily in a pot. Because there are hundreds of different cultivars and varieties, the only way to know the eventual size of a dahlia is to read the plant tag or the description in the catalog or online—something you should definitely do. When growing dahlias in pots, choose varieties that top out at 2 feet or less when fully grown.

Most dahlias have the same planting, watering, and feeding needs, so your space and which variety you prefer are the biggest factors in deciding which dahlia to get. To help narrow down your options, here are some the basic types of dahlia flowers you'll find:

Ball dahlias. Like the name suggests, these dahlia flowers have a rounded shape that looks like a golf, tennis, or even softball depending on size. Look for the tightly packed, rounded petals that give these dahlias their signature look. Many ball dahlia varieties have a reputation for producing lots of flowers, making a great choice for beginners. Also be on the lookout for their miniature cousins, pompon dahlias.
Cactus dahlias. With their distinctive long, spiky petals, you can't miss cactus dahlias! You can also find semi-cactus dahlias, which feature similar long petals, only wider at the center of the flower.
Decorative dahlias. Between the rounded ball dahlia and spiky cactus dahlia, you'll find decorative dahlias. Often divided into formal and informal decorative dahlias, these lush, full blooms come in a wide range of colors and sizes.
Waterlily dahlias. With layers of flat rounded-edge petals, these dahlias resemble their namesake, the waterlily. These flowers grow on long, sturdy stems, making them a cut-flower favorite.
Anemone and collarette dahlias. Due to their unique centers, these two dahlias often get grouped together. Anemone dahlias are recognizable by the cushion-like cluster of small, tubular petals at the center while collarette dahlias have a layer of small, flat petals around the center.
Dinnerplate Dahlias. The showstoppers of dahlias, dinnerplate blooms can grow to be quite large—between 8 and 10 inches across! Getting those big, gorgeous blooms does mean a little extra work on your part, but the rewards are stunning.
Single dahlias. Don't underestimate simple! Even though single dahlias only have a single row of petals, these blooms can be just as stunning as their fuller many-layered cousins.

Planting Dahlias

Understanding Dahlia Tubers

While "baby" dahlias are sometimes called bulbs, they're really tuberous roots. Healthy dahlia tubers have long bodies with narrow necks and a head or crown at the top. The crown is where you'll find the "eyes"—tiny bumps or raised areas that'll eventually sprout your plant. The eyes can sometimes be red or pink, but often they're a similar color to the rest of the tuber. Without eyes, your tuber will not grow into a beautiful dahlia plant. Unless your tubers are very dried out, you typically don't need to soak them before planting.

When to Plant Dahlias

Look for dahlias when you shop for summer flowering bulbs. Plant dahlia tubers outside after the final frost of the year, which can be early as mid-April in the South or as late as June in colder climates. If you live where you can't plant until early summer, you can give your dahlias a head start by planting them in pots indoors in April. Once warm weather arrives, you can either move the pots outside or transplant the dahlias into the ground or a raised bed.

Where to Plant Dahlias

Dahlias are sun lovers, so plant them where they'll receive at least 6 hours of sunlight per day. In the South and other warm climates, a bit of afternoon shade during the hottest part of the day is fine, as long as they receive sun the rest of the day. If you're planting in containers, be sure to place them where they’ll receive plenty of sunshine.

Soil for Dahlias

While easy to grow, dahlias do appreciate and thrive in soil that's right for them, which means no heavy clay or soils with standing water. If you're planting in-ground, you can amend your soil with Miracle Gro® Garden Soil All Purpose, our garden soil that gives you bigger, more beautiful (vs unfed plants). If you prefer an organic option, try Miracle-Gro Organic™ Raised Bed & Garden Soil, which is crafted with organic compost to help rejuvenate native soils.

For container planting, you can't go wrong with Miracle-Gro® Moisture Control® Potting Mix, our potting mix that protects against over- and underwatering. Organic growers may prefer Miracle-Gro Organic™ Outdoor Potting Mix with compost to boost water and nutrient retention.

How to Plant Dahlias

In-Ground Planting

First, determine the ideal spacing for the types of dahlias you plan to grow. Remember to review plant tags for the expected mature size and proper spacing.
Prepare the soil by mixing 3 inches of Miracle Gro® Garden Soil All Purpose or Miracle-Gro Organic™ Raised Bed & Garden Soil into the top 6 inches of existing soil, or focus on individual planting holes by blending equal amounts of garden soil and native soil.
Lay the dahlia tubers out on the soil, properly spaced, then bury them 4 to 6 inches deep with the eyes facing upward.
Next, put down a thin layer (1 to 2 inches) of mulch to help keep the soil consistently moist. We like Miracle-Gro Organic™ All Natural Mulch.

Note: If you're transplanting or purchasing a young plant, you can follow the same directions as above. Just make sure that the hole is big enough to fit your plant and that you've spaced your plants properly.

Containers

Choose a pot that is about 3 to 4 times as wide as the tuber or clump of tubers.
Fill the pot with either Miracle-Gro® Moisture Control® Potting Mix or Miracle-Gro Organic™ Outdoor Potting Mix, leaving space to bury your tuber 4-6 inches deep with an inch of space at the top (to prevent spillage when watering the plant).
Place tubers in the soil with the eyes facing upward.
Cover with additional potting mix. Gently tap down.
Place your pot where it will receive at least 6 hours of sunlight per day.

Dahlia Care

How to Stake Dahlias

Since dahlia flowers can be heavy and you don't want the stems to break just as the blooms are about to open, you'll want to give each plant some support. For best results, do this either at planting time or before the plants are over 6 inches tall. Simply use a wooden or bamboo stake or a tomato cage for individual plants. Growing a bunch of dahlias in a row? Use stakes and twine to create a lattice system along the row by weaving the twine between the stakes, leaving holes for the dahlias to grow through.

How to Water Dahlias

Dahlia's watering needs change as the plant grows. After planting, only mist the ground lightly (or not at all)—dahlia tubers are susceptible to rot. Once you see new growth, start watering regularly, keeping the soil about as damp as a well wrung-out sponge. The bigger the plant, the more water it will use, so you will likely have to water more as the summer progresses.

How to Feed Dahlias

To maximize blooms, you'll want to complement the great soil with just the right plant food. Formulated for blooming plants, Miracle-Gro® Water Soluble Bloom Booster® Flower Food can be used every 7-14 days to provide essential nutrients to your dahlias. For those who prefer an organic solution, Miracle-Gro Organic™ All Purpose Plant Food grows healthier, more resilient plants (vs unfed, when used as directed). Simply sprinkle this granular organic plant food around your plants to feed them for up to 3 months. When using any plant food, remember to follow all label directions so your plants can reap the most benefit.

How to Prevent Problems with Dahlias

Snails and slugs are the biggest pest problems for dahlias, and they can be controlled by sprinkling diatomaceous earth or a snail and slug control product. Sometimes spider mites can be an issue, and neem oil can be used to take care of them.

In addition to garden bugs, hot, humid summers can cause powdery mildew to coat dahlia plant leaves. To prevent powdery mildew, keep leaves as dry as possible when you water the plants. Also, make sure to space them properly when you plant to allow for ample air flow. Whenever you see diseased or damaged leaves or flowers, remove them as quickly as possible.

How to Deadhead and Disbud Dahlias

Want more dahlia flowers for a longer period of time? Snip off flowers as soon as they begin to fade. Using a sharp knife or sheers, cut the flower stem all the way back to a leaf. This encourages new flowers and also keeps your plant looking its best.

You can also try "disbudding," which is when you remove some flower buds so the plant can put its energy into growing fewer, but larger, flowers. This is especially important for those dinnerplate varieties. To disbud, just pinch off the two buds near the base of the main flower stem and let the main flower open. You'll be able to recognize the main flower because it grows on a longer stem than the side buds. When you remove the side buds, remember to pinch or use sharp sheers to snip at the base where it connects to the main stem.

How to Harvest Dahlias

You can enjoy your dahlia blooms on the plant, or bring them inside to brighten your space with a beautiful bouquet! Cut dahlias in the morning before the heat of the day sets in. Use a sharp pair of shears or harvest snips and make sure to choose blooms that are fully open, with no green center visible. Unlike peonies, dahlia buds won't open after they're cut. Be sure to change the water every 2 to 3 days.

How to Overwinter and Divide Dahlias

Dahlias are a perennial plant in zones 8 and higher, which means those in warmer regions can leave their dahlia tubers in the ground and wait for them to come back next year. In colder areas, though, you'll need to bring tubers inside and replant them next year. One advantage of saving tubers is that you may find yourself with more plants than you started with by dividing your tubers. If you don't have room in your garden, give a few away to friends!

For those in warmer climates, your dahlia tubers can still rot during winter rains. Also, tubers need to be divided every 2-3 years to avoid overcrowding plants. Keep an eye on weather patterns in your area, and watch out for weak plants that aren't producing as many blooms.

Here's how to overwinter and divide dahlias:

After the first frost in late summer or early fall, dig up the dahlia tubers and cut off the stems and excess roots.
Let the tubers sit in a dark, cool place for a few days to dry out.
Pack tubers between sheets of newspaper and store them in a cool, dry spot, such as a closet or insulated garage.
After the last frost of the season, take out your tubers and decide if you need to divide them. If your tubers are in a big clump, it may be best to divide them.
To divide dahlias, simply break apart the clump of tubers. Each tuber should have a body, a neck, and, most importantly, eyes on the crown. If a tuber does not have eyes, it will not grow into a new plant.
Replant your dahlia tubers using the instructions above. Watch your dahlias come back to life!

Dahlias are a wonderful addition to any garden. By following these simple tips, you'll enjoy beautiful blooms all season long.