How to Grow Dahlias in Pots

Overview

Dahlias, discovered by the Swedish botanist Anders Dahl in the mountains of Mexico, are cheery pom-poms of color in the summer. These tuberous perennials range in size from dwarf 6-inch plants to bushes reaching 4 feet high. The flowers come in red, orange, purple, lavender, yellow--almost every color except brown, green and true blue, according to Iowa State University Extension. The dwarf or smaller varieties make excellent container plants, and varying the heights of your dahlias adds texture and interest to your patio.

Planting

Step 1

Choose your dahlia variety. While dwarf or low-growing varieties work best in containers, you can grow full-sized plants if your pot is large enough. You'll need to stake cultivars that grow taller than 2 or 3 feet.

Step 2

Choose your container. Dahlia tubers require pots at least 8 inches wide. A pot that is wider than it is tall will give the wide-spreading tubers room to grow.

Step 3

Rinse your pot with a 10 percent solution of bleach to get rid of any diseases or pests that may have lingered from previous uses.

Step 4

Fill your container half-full with commercial potting mix. If you prefer to make your own, Iowa State University Extension recommends combining equal amounts of sterilized soil, perlite and peat moss. Add a slow-release, all-purpose fertilizer (5-10-5 or 5-10-10) to the mix.

Step 5

Place the tuber on the soil, and cover it with soil. Add 2 more inches of soil on top of the tuber, then water thoroughly.

Step 6

Place the pot in full sun when the plant begins to emerge from the soil.

Care

Step 1

Keep your tubers indoors until after the final spring frost date for your area. Frost can damage or even kill your dahlias.

Step 2

Fertilize with a liquid all-purpose fertilizer (5-10-5 or 5-10-10) in July.

Step 3

Water twice a week, giving your dahlias at least 1 inch of water. If your plants start to wilt in the heat of the summer, water more frequently. Adding mulch to the top of your container will help retain moisture.

Step 4

Get the best blooms, ISU Extension notes, by removing the axillary buds just beneath the main bud on the stem where the leaves meet. If the axillary buds are left on the plant, they will develop and flower--but this reduces the quality of the bloom and leads to weaker stems. Remove all spent blooms to promote flowering.

Step 5

Remove the brown leaves and stems from your dahlia after the first killing frost. Leave the tubers in the soil for two weeks. Then remove them and wash off as much soil as possible, taking off the rest of the stalk.

Step 6

Let the tubers dry for a day, then store them upside down in a box and cover them with peat moss, wood shavings or vermiculite.

Step 7

Label the boxes with the name of each variety, then store them in your basement or a garage, where the temperature won't drop below 40 degrees F.