How to Grow Dahlias Indoors

A showy dahlia bloom

Dahlias are popular perennial landscaping plants because of their beautiful foliage, bushing nature, and their showy blooms. Originally native to Mexico, Central America and Columbia, dahlias grow to 3 to 4 feet tall in the garden, and sport a wide variety of blossom sizes and colors. From the small button sized pom pom varieties to the large dinner plate sized varieties, dahlias come in colors ranging from white to red and everything in between with the exception of green and blue. While dahlias can grow large when planted in the yard, with care and pruning dahlias can be grown indoors as well.

Things You'll Need

• Dahlia tubers
• Containers
• Bleach
• Knife
• Drill with 1/8 inch bit
• Soil-less potting mix
• Biodegradable coffee filters
• All-purpose fertilizer (5-10-5 or 5-10-10)
• Garden stakes
• Garden ties

Instructions

Planting Preparation

1. Divide the tubers using a sharp knife, cutting carefully to ensure that at least one eye and one tuber is attached to each piece. Shoots emerge from the eyes, which are not in the tubers, but on the crown. To determine where the eyes are, place the crown and tubers in a shallow pot with a moist soil-less gardening mix for one or two weeks; shoots that begin growing from the crown are the eyes.

2. Wash all containers thoroughly with a diluted solution of one part bleach to ten parts water in order to kill any organisms that may inhibit dahlia growth or cause infestations or plant disease. Let dry.

3. Drill holes in the bottom of the containers if they do not have plenty of drainage. The containers must be at least 8 inches wide, but preferably 12 inches wide. Pots that are wider than they are tall are best for dahlias.

4. Cover the bottom of the pots with one to two layers of coffee filters, to keep soil from draining from the pot, and to keep insect pests from invading your pots.

5. Fill the containers with moist potting soil until 1/3 full.

Planting and Growing

1. Place one to three tubers with crown eyes in the center of each pot, making sure that the sprouting eyes are facing upward. Cover tubers with potting mix until barely covered. If the eyes have already begun to sprout, do not cover the sprout entirely with soil.

2. Add more potting soil to the containers as they grow, making sure not to cover the shoots. After a couple of weeks, the dahlia tubers will begin to grow grow leaves.

3. Water lightly. Every week or so add more soil and water lightly, allowing to dry out to a depth of 1 inch between watering.

4. Stake the dahlia when stems are 6 inches tall. Push stakes down firmly into the container, avoiding the tubers. Tie the stems loosely to the stakes with plant ties.

5. Fertilize the plants with an all-purpose fertilizer every three to four weeks during the growing season.

Tips & Warnings

• Place your dahlia in a sunny location away from drafts, where the temperature maintains about 55 degrees F, on pans or trays to protect furniture or floors from drainage water damage.

• Stake your dahlias well to prevent stem bending and breakage.

• Cut stems before they break and display in vases.

• Division of the tubers (roots and crown/bulb) is the easiest method of dahlia propagation, but they can also be grown from seed or cutting.

• Do not over water dahlias; tubers will rot if sitting in water.

References

• The Ohio State University Extension Fact Sheet: Growing Dahlias
• Oregon State University Extension Service: Dahlia Culture

Resources

• Swan Island Dahlias: How To Grow Dahlias
• The American Dahlia Society: Fundamentals of Growing Dahlias