Can I Plant Dahlia in a Pot?

Choosing the Right Variety

• Dahlias suitable for containers are known as low-growing or border dahlias. They produce short, bushy plants 12 to 18 inches tall. Examples of low-growing dahlia varieties available in the nursery trade are Singer, Art Deco or Monet. Although all dahlias will grow in a suitable container, keep in mind taller varieties need to be staked or protected from high winds as dahlia plants are notoriously brittle.

Choosing a Container

• Choose a container that is clean, well-draining and at least 12 inches in diameter for each tuber you are planting. Dahlias must have plenty of space and well-drained soil as dahlia bulbs easily rot if soil conditions are too moist or the tubers are crowded. A container with several drainage holes along the bottom side of the container is better than a container with one drainage hole in the bottom that is easily clogged by roots and compacted soil.

Planting Instructions

• Plant dahlias in the spring after all danger of frost has passed. The potting soil should contain vermiculite or perlite to allow for easy drainage. Do not use garden soil because it may contain disease-causing organisms or insect eggs. Avoid using soil containing clay as clay holds water and does not drain easily. Cover the drainage holes of the container with a section of a coffee filter so soil will not escape. Fill the container with enough potting soil so the tubers are planted 4 inches deep counting from the growing bud.

  Place the tuber in the container on top of the layer of potting soil so the eyes or buds are facing up. A tuber may be round or tapered with the buds along the side. Cover with potting soil and water gently to settle the soil. Place the container where it receives at least eight hours of direct sunlight each day. You may find that the location is too warm and the potting soil dries out quickly or the dahlias wilt from the heat. If this is the case, be prepared to move the container where the dahlias are protected from the hottest afternoon sun. An ideal location is where dahlias receive their required amount of sunlight in the first part of the day.

  Keep the soil barely moist until new growth appears, and water as needed to keep the plants vigorous and prevent wilting. Do not overwater the tubers before new growth appears or the tubers will rot.

Plant Care

• Fertilize every 10 days with a water-soluble fertilizer diluted to half-strength. Frequent applications of a diluted fertilizer are better than occasional heavy applications. Always water the plants before adding fertilizer. For best results, use a time-release granular fertilizer appropriate for container plants. Time-release fertilizers provide a constant source of nutrition during the entire growing season without numerous applications. Use fertilizers as directed and never over-fertilize plants.

  In the fall, withhold any new fertilizer applications beginning 30 days from the first average freeze date. Allow the plants to die back without pruning as they will naturally decline as the days shorten. Once the foliage is dead, trim off the foliage at soil level and withhold water and fertilizer until spring when new growth appears.

  If you live where the soil in the pot can freeze solid, remove tubers from the container, wash the dirt off and place them in a warm, well-ventilated location where they can dry. Store the tubers in a well-ventilated location where the temperatures are 33 to 35 degrees Fahrenheit until spring when they can be replanted.

Pruning

• Prune or pinch off the tip of the main stem of the dahlia plant when the main stem has three sets of leaves. This is done by pinching back the stem to a place that is 1/4 inch above the third set of leaves counting up from the soil.

  Remove spent blossoms by cutting the stem back to a point 1/4 inch above a leaf node, which is the raised area on the branch where leaves are growing. The farther back you prune, the bushier and sturdier the plant will become. Don't cut the stem back to the main branch or the plant will grow tall and lanky.