Gardening Gardening Basics Container Gardening

How to Grow Dahlias in Pots

dahlias growing in a pot

The Spruce / Adrienne Legault

Growing dahlias in pots is easy with the right watering techniques, soil, and light exposure that results in blooms that can go from simple to almost psychedelic in color and form. Dahlias make luxurious cut flowers, and as perennials, they are normally planted in the ground. Depending on the size of the variety, they can also play the role of a thriller or filler plant in a mixed container.

Most dahlias bloom from midsummer through fall in most areas, so you must expect your container plants to be without color until bloom time. The foliage, however, can provide a nice architectural structure in a mixed planting in a large pot. Read on for all the steps to growing dahlias in pots.

Best Dahlias to Grow in Pots

Buy dahlia tubers online or in nurseries and some big box stores. Many nurseries also sell dahlias already started in containers. Dahlias come in a huge range of flower sizes as well as plant sizes. If you are looking for very large flowers, look for "dinner plate" dahlias. If you are looking for shorter plants look for miniatures, or "low-growing" dahlias. Short, dwarf, and compact dahlia varieties are best for growing in pots. Here are a few to try:

  • 'Sunshine': Yellow petals and orange centers, up to 24 inches tall
  • 'Star's Favorite': Pink petals growing to 2 feet high
  • 'Scura': Compact with tangerine blooms, up to 18 inches tall
  • 'Park Princess': Pink petals, up to 24 inches tall
  • 'Impression Fuego': Bright red and gold petals, up to 20 inches tall

Growing Dahlias in Pots

Dahlias grow well in pots, though you need to be very careful not to let them repeatedly dry out. They also will need to be regularly fertilized during the growing season, and many will need to be staked so they don't fall over. It's also a good idea to put the taller varieties in heavy pots, so a stiff wind doesn't blow them over. Repotting dahlias in heavy-duty plastic containers is a must if the plant becomes too large for its current container.

dahlias growing in a pot

The Spruce / Adrienne Legault

Planting in Pots

Know When to Plant

If you live in a colder climate and want your dahlias to bloom earlier, you can plant them indoors about six weeks before the last frost. However, if you do plant them inside, it's a good idea to provide supplemental lighting once the plant breaks through to the surface of your soil. For lighting, you can either use shop lights fitted with one cool and one warm fluorescent bulb or special "grow lights."​ If you are starting your dahlias in pots outside, wait until all danger of frost has passed, or make sure you can move your pot inside if frost is predicted.

Choose a Pot Size

For most dahlias, you want a large pot, though it doesn't need to be very deep. Many varieties would do well in a 12- to 14-inch diameter pot, at least 12 inches deep. Also, make sure the pot has good drainage because the tubers will rot if left to sit in water.

Use the Right Soil

Choose a good all-purpose, fast-draining potting mix and stir in a slow-release fertilizer, following the label for directions on quantity. Dahlia tubers can be a bit unwieldy and large so unless you are going to separate them, you will need to be careful when planting in containers.

Make sure that the potting mix surrounds all the parts of the tuber without leaving any air pockets, and that the top of the plant is pointing upward (look for eyes, like you would find on a potato or where the stem used to come out of the bunch). Mound a few inches of potting soil on the bottom of the pot, forming a little bit of a hill, and balance the tuber on the mound. Then carefully fill in around the tuber with potting soil, firming it around the tuber gently to avoid breaking them. Some people recommend layering the soil and slowly filling up the pot as the plant grows.

How to Care for Dahlias in Pots

Water

After planting dahlia tubers in containers in the spring, do not water them until you spot green growth sprouting above the surface. Dahlias do not need water until their root system develops or root rot can develop.

Once sprouted, begin watering once or twice a week to keep the soil moist but not soggy. Water the container deeply, especially if you have planted large tubers 6 inches deep. If summer days are especially hot and dry, you may need to water container plants more frequently, possibly daily, to ensure that you never let the soil dry out.

Light

Dahlias like full sun, though they don't like to get searingly hot. If you live in a warm climate or your pot is in a hot spot (in a corner or on concrete where the surface gets hot) move your pot into a shady spot during the heat of the day.

Stakes and Support

Most dahlias will have to be staked so they don't fall over. Also, depending on the depth of your pot, a single stake might not do the trick of holding up the plant either—particularly in a stiff breeze. You can make a teepee out of bamboo, or, use garden plant ring stakes to hold up the flowers.

Pruning

Pinch the top tips off dahlias, right above a set of healthy leaves, when they reach about 16 inches tall, This helps multiple new stems grow in place of the pinched central stem.

Good nurseries often sell dahlias already potted. This can be an advantage, particularly for the dinner plate variety because they will typically be properly pruned for the best and biggest blossoms.

Deadheading

For more flowers and fuller blooms, deadhead dahlias regularly after they die back.

Overwintering Dahlias in Pots

If you live in a cold climate it's best to overwinter dahlia tubers in pots. Wait until after a couple of frosts, then follow these steps:

  1. Cut off the dead foliage a few inches above the soil.
  2. Let the pot dry out in your garage or shed.
  3. After drying, carefully dig up the tubers and brush off all the extra dirt.
  4. Put brushed-off tubers in a cardboard box. Storing dahlias in dry, cool conditions is best, such as an open basement with good air circulation.
  5. In the spring, carefully inspect the tubers and replant only those that are firm and not desiccated or soft.
dahlia tubers

The Spruce / Kerry Michaels

dahlia close up

The Spruce / Adrienne Legault

FAQ
  • Will potted dahlias come back every year?

    Dahlias in pots can be perennials and will come back in pots every year if they are correctly overwintered.

  • Do dahlias like sun or shade?

    Dahlias prefer full sun for better blooms.

  • How long do potted dahlias last?

    If the tubers are properly overwintered, they can last a couple of seasons or more. When overwintering, dig them up or keep them in a pot that's located in a cool, dry, dark place that won't freeze. You do not need to water the pot, just let the tubers stay dry as they are dormant.

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  1. Dahlias. University of Georgia Extension.