Dahlias Are The Perfect Flowering Plants for Small Spaces—How to Grow Them (2024)

Growing dahlias in pots is an easy way to enjoy these colorful flowers, even if you're short on space. The right watering techniques, soil, and light exposure will give you abundant blooms from midsummer until fall. Dahlias make excellent cut flowers and can play the role of a thriller or filler plant in your container.

Their foliage provides a welcome architectural structure in a mixed planting in a large pot. Read on to learn about growing dahlias in pots, plus tips for planting, care, and more.

How to Plant Dahlias in Pots

Plant dahlias outdoors in pots once all danger of frost in your area has passed. Put each tuber in a container that is at least 12 inches deep, 12 inches tall, and 12 inches wide so plants have plenty of space to develop their roots. Use a pot with plenty of drainage holes in the bottom.

When to Plant

If you are starting your dahlias in pots outside,wait until after your region's last frost date, or make sure you can move your pot inside if a late frost is predicted. Ideally, the soil temperature should be at least 60°F. 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 plant them inside, it's a good idea to provide supplemental lighting once the plant breaks through the soil surface. Use shop lights fitted with one cool and one warm fluorescent bulb or grow lights designed for plants.​

Pot Size

Use a pot that's 12 to 14 inches in diameter and at least 12 inchesdeep. Plant taller varieties in heavy pots to keepa stiff wind fromblowing them over.

Make sure the pot has good drainage; the tubers will rot if left to sit in water. Repot dahlias in a heavy-duty plastic container if the plant becomes too large for its current container.

Tuber Spacing

Plant just one dahlia tuber per container to avoid overcrowding, as hahlia tubers can be a bit unwieldy and large. Position tubers in the soil with the stem end facing up. Cover with soil so the top of the stem end is just barely below the soil line.

Soil

Use an all-purpose, fast-draining potting mix amended with slow-release fertilizer granules according to the directions on the label. Mound a few inchesof 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 gently around the tubers to avoid breaking them. Make sure that the potting mix surrounds all the parts of the tuber without any air pockets.

How to Care for Dahlias in Pots

Water

Water immediately after planting dahlia tubers in containers. After that, wait to water them until you see green growth above the soil surface. Watering too much before your dahlias have developed their root system can cause tubers to rot.

Once the plants have sprouted, water often enough to keep the soil moist but not soggy, around one or two times per week. Check soil moisture regularly to keep the soil from drying out completely. If summer days are especially hot and dry, you may need to water container plants more frequently, possibly daily.

Light

Dahlias like full sun, though they don't thrive in excessive heat. Keep your potted dahlias in a spot that gets at least 6 hours of direct sunlight per day. If you live in a warm, sunny region, consider keeping your container in a place that gets some afternoon shade to protect your dahlias during the hottest part of the day.

Stakes and Support

Most full-sized dahlias, especially those with large blooms, need stakes to keep them from falling over. Add stakes at or shortly after planting. Use sturdy stakes made from wood, bamboo, or even metal rebar to ensure that they'll keep your plants upright. Tomato cages can even work in a pinch.

You may need more than one stake per plant, especially if using bamboo poles. Tie the plant's stems loosely to your stakes with twine, garden clips, or twist ties as they grow.

Pruning

Pinch the tips off of dahlias when plants reach about 16 inches tall. Remove the growth at the very end of the stem, just above a set of healthy leaves. This will encourage multiple new stems grow in place of the pinched central stem.

Deadheading

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

Best Dahlias to Grow in Pots

Buy dahlia tubers online or in nurseries and some big box stores. Many nurseries also sell dahliasalready 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
  

Starting Dahlia Seeds Indoors

Start dahlia seeds indoors 6 to 8 weeks before your region's last frost date. Use a seed starting potting mix and seed trays with drainage. Moisten the growing medium with water, press the seeds into the soil surface, and cover them with a very thin layer of soil.

Since the germination rate for dahlia seeds can be as low as 30 percent, it's a good idea to sow more seeds than you'll need to ensure you get enough plants. Spritz the soil to keep the growing medium moist, and use clear plastic covers or plastic wrap to hold in moisture. Keep the plants in a warm place or use a heat mat during germination.

Once seeds germinate, position a grow light about 2 inches from the seedlings and set it to run for 14 to 16 hours each day. Begin hardening off dahlia seedlings a few weeks before your last frost date. Wait to transplant seedlings outdoors until the soil temperature is at least 60°F.

Note that dahlias grown from seed won't be identical clones of their parent plants the way dahlias grown from tubers would be, so expect to see some variation in seed-grown dahlias.

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 fall frosts, then follow these steps:

1. Cut off the dead foliage a few inches above the soil.
2. Bring containers indoors and let the pot dry out in your garage or shed.
3. Dig up the tubers and brush off excess soil. Place tubers in a paper bag, cardboard box, milk crate, bin, or other well-ventilated container.
4. Store dahlias in dry, cool, dark conditions through winter.
5. Inspect the tubers in spring and replant only those that are firm and not desiccated or soft.