Grow Dahlias in Pots
Dahlias are bright, beautiful flowers that come in a wide variety of colors. Due to their height, however, many gardeners may feel skeptical about planting them in pots. Dahlias can thrive in pots as long as the container is large enough, but varieties that are three feet in height or taller may need additional support from stakes.
Contents
Steps
Preparation
- Select a variety of dahlia suited for container growing. Dwarf and low-growing varieties work best, but nearly any type can be grown if you have a large enough pot.
- Pick out a large pot. A good container to start with should be approximately 12 inches (30.5 cm) deep by 12 inches (30.5 cm) in diameter. Larger varieties may need even larger containers, however, especially if the flowers exceed 3 feet (0.91 m) in height.
- Choose a heavy pot. A light pot may not be sturdy enough, and the dahlia could become top heavy as a result.
- Drill additional drainage holes. This step may not be necessary if the container you use already has several large drainage holes that allow excess moisture to drain quickly. If your pot has small holes or only has one center hole, you may need to drill a few extra holes to improve drainage.
- Clean the pot. A dirty pot could spread disease, and hidden insect eggs may be lying in wait at the bottom of the pot. Remove these threats by cleaning the container before you plant. Simple soap and water will usually do the trick.
- Pick out a coarse potting mix. Standard potting soil alone is too porous and may lead to pour bud formation. A good potting mix includes both potting soil and garden soil, or potting soil and compost. Alternatively, non-soil mixes made of fine bark, peat, and various minerals may also work.
Planting
- Plant the tubers before the roots start to grow too long. Long roots will become entangled, and separating the roots will damage them. If the tubers need to spend time forming new roots, the flower's upward growth and bloom will be delayed and may be minimized for the season.
- Start sometime in April or May.
- If starting the dahlias in pots that sit outdoors, wait until mid-April through all of May.
- If starting the flowers indoors, you can plant the tubers in early April.
- Place one or two biodegradable coffee filters over the holes in the bottom of your pot. Filters wick away moisture, preventing the roots from drowning. Placing gravel at the bottom of your pot will accomplish the same task, but a dahlia's roots need all the space they can get to grow, and the coffee filter method takes up much less room than gravel would. Placing filters over the holes may also prevent bugs from getting in.
- Fill your container a third way full with your potting mix. Do not pack it tightly; allow the soil to remain loose.
- If using a pot deeper than 12 inches, you may need to fill it with more soil. When all is said and done, dahlias need to be planted about 6 inches deep, and there should be an inch between the surface of the soil and the rim of the pot at the end of the potting process.
- Moisten the soil. Make it damp, but do not soak.
- Mix a handful of bone meal and fertilizer into the soil. Dahlias require a lot of nutrients to thrive. Fish or seaweed fertilizer can provide additional micro nutrients, as well.
- You can also purchase a copolymer slurry from a gardening store instead of using bone meal and fertilizer. Follow the package for usage directions.
- If mixing the slurry, fertilizer, or bone meal into the soil causes the coffee filters to move from the bottom of the pot, remove the soil from the pot and mix the elements together that way. Simply add it back in, over the repositioned filters, once everything is combined.
- Plant the tuber in the soil. Lay it down horizontally and leave at least 1/4 inch space between the root end of the tuber and the side of the pot. If an eye has already developed, center the eye in the middle of the pot and allow it to face upward. The sprout will come through from this eye.
- Cover the dahlia tuber with pre-moistened soil. Do not bury the tuber at this time, however. Instead, cover it with a minimal amount of soil so that you may monitor its growth.
- Allow any exposed eyes to remain above the soil. Lightly spritz the exposed surface of the tuber with just enough warm water to moisten the surface.
- Add more soil as the stalk grows. Do so carefully to avoid damaging the stalk, since the stalk is still fairly fragile at this stage. Never cover the top set of leaves. Continue adding soil until only an inch of empty space remains between the top of the soil and the rim of the pot.
- Insert a stake into the pot, and tie the stalk to the stake. Large dahlia varieties need extra support to prevent the stalks from breaking off. Use a four foot stake with most varieties. Metal works best due to its sturdiness. The base of the stake should touch the bottom of the pot, and the stake itself should be firmly held in place by the soil and/or wires tied to holes drilled into the sides of the pot.
Care
- Water the tubers deeply once the stalk extends above the rim of the pot. Give them a thorough watering two or three times a week. Dahlias growing in hot, dry climates may need daily watering. Never allow the soil to get soggy, however.
- Place the pot in full sun. Dahlias grow best with six to eight hours of direct sunlight.
- Supplement sunlight with fluorescent plant lights if started indoors. Many indoor dahlias do not receive enough light from the sun, and a plant light may be necessary to spur proper growth. Set the light about six inches above the top rim of the pot for newly planted tubers and raise the light as the plants grow.
- Fertilize the flowers once every two weeks from June through September. Use a low nitrogen fertilizer, and avoiding over-feeding.
- Remove bottom leaves late in the season, usually around mid-July. The removal of these leaves improves air circulation, which reduces the risk of mildew.
- Spray your dahlia with fungicide or insecticide as needed. Dahlias are subject to attacks from mold, earwigs, slugs, spider mites, aphids, and cucumber beetles.
Tips
- When you are using dahlias as cut flowers, run the ends of the flowers through hot water just on the cut part.This helps seal in moisture, which help prolong your cut flowers life.
- If you live in a cold climate, over-winter your dahlia tubers indoors. Dig up the tubers two weeks after the first frost kills the tops of the plants. Wash off the dirt and air dry for a day. Wrap them in paper and store in a cool, dry area.
Things You'll Need
- Dahlia tubers
- Large, heavy pot
- Potting soil
- Low-nitrogen fertilizer
- Fluorescent plant light
- Metal stake
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