Growing dahlias in containers is a great way to have colorful flowers at home even if you don’t have enough space. By providing the right watering techniques, soil, and light exposure you will get abundant blooms from mid-summer until fall. These excellent cut flowers can be a thriller or filler plant in your pot.
Their foliage gives a great architectural structure in a mixed planting in a large pot. Below, we give you the tips and tricks about growing these dahlias in pots, and how to take care of them for healthy growth.
How to plant dahlias in pots
Plant dahlias outdoors in pots once the cold has passed. Put each tuber in a pot at least 12 inches deep, 12 inches tall, and 12 inches wide so that these plants have enough space to expand their roots. It would be best if you used a pot with plenty of drainage holes in the bottom.
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When to plant dahlias
If you’re planting your dahlias in pots outside, we recommend waiting until after your region’s last frost. Alternatively, you can also move your pot inside if a late frost is predicted. For dahlias to bloom properly, the ideal soil temperature should be at least 60°F. If the place where you live is colder and you want your flowers to bloom earlier, you can plant them indoors about six weeks before the last frost.
Having said that, if you plant them inside, it’s a great idea to give them supplemental lighting once the plant surfaces through the soil. You can use shop lights fitted with one cool and one warm fluorescent bulb or grow lights designed for plants.
Pot Size
You can use a pot that is 12 to 14 inches in diameter and at least 12 inches deep. It is best to plant taller varieties in heavy pots to keep a strong wind from knocking them over. Also, make sure that the pot has some good drainage because the tubers will start rotting if left in water for long. It is suggested to repot the plant in a heavy-duty container if the plant is too big for its existing container.
Tuber Spacing
It is necessary to remember to plant just one dahlia tuber per pot as it avoids overcrowding as dahlia tubers can be a bit large and messy. Keep tubers in the soil with the stem end facing up. Finally, cover with soil so the top of the stem end is just below the soil line.
Soil
For Dahlia’s growth, use an all-purpose, fast-draining potting mix that contains slow-release fertilizer granules as per the directions on the label. Pile a few inches of potting soil on the bottom of the container, forming a hill-like look, and balance the tuber on the mound.
After that, carefully fill the potting soil around the tuber and gently firm it around the tubers to avoid breaking them. Ensure that the potting mix surrounds all the parts of the tuber without any air pockets.
How to care for Dahlias in pot
Water
It is essential to water the dahlias immediately after planting dahlia tubers in pots. After watering, wait to water them until you notice green growth above the soil surface. If you overwater your dahlias that have already developed their root system, it might cause root rot.
Once you see that the plants have sprouted, water them often to keep the soil moist but not soggy. It should be around once or twice a week. Keep a check on the soil moisture regularly to keep the soil from drying out completely. If the summers are scorching hot, then you need to water the container plants more often, daily if needed.
Light
Dahlias prefer full sun, but they don’t do well in excess heat. Keep your potted dahlias in a place that gets at least a good 6 hours of direct sunlight per day. If your region is warm and sunny, it would be best if you keep your pot in a place that gets some afternoon shade. It protects your dahlias during the hottest time of the day.
Stakes and support
Most mature dahlias, especially the ones that have large blooms, need support to prevent them from falling over. So, you can add stakes at or shortly after planting. Use sturdy stakes made from wood, bamboo, or even metal rebar to make sure that they will keep your plant straight and upright. Tomato cages will also come in handy in a pinch.
You may require more than one stake per plant if you’re using bamboo poles. Tie the dahlia plant’s stems loosely to your stakes with twine garden clips or try twisting ties as they grow bigger.
Pruning
Pinch off the tips of dahlias when the plant reaches about 16 inches tall. Remove the growth at the very end of the stem, just above a set of healthy, green leaves. Doing this will encourage many new stems to grow in place of the pinched central stem.
Deadheading
Once the dahlias die back, deadhead them regularly if you want fuller blooms and flowers.
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Best dahlias you can grow in pots
You can also purchase Dahlia tubers online or in nurseries and some big box stores. Many nurseries often sell dahlias in containers. These plants come in an extensive range of flower and plant sizes. If you love large flowers, look for dinner plate dahlias. And if you’re looking for shorter plants, short, dwarf, and compact dahlia varieties are great for growing in containers. Here are a few options 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. For this purpose, use a potting mix and seed trays that have proper drainage. The mix needs to be moist so spray it with water and press the seeds into the soil surface. After that, cover them with a thin layer of soil.
You have to know that the germination rate for dahlia seeds can be as low as 30%. That means sowing more seeds to ensure that you’re getting enough plants. Spritz the soil often to moisten the soil and use clear plastic to cover or to hold in moisture. During germination, keep the plants in a warm space or you could use a heat mat during germination as an alternative.
Once you realize the seeds have germinated, keep a grow light about 2 inches from the seedlings and let it be there for 14 to 16 hours each day. Hardening off dahlia seedlings a few weeks before your last frost date is important. You have to wait to transplant seedlings outdoors until the soil temperature is 60°F at minimum.
You have to know that the dahlias you grow from seed won’t be similar clones of their parents the way dahlias grown from tubers would be. You should not be surprised to see some variation in seed-grown dahlias.
Overwintering Dahlias in pots
If you live in a cold climate, overwintering dahlia tubers in pots would be the best idea. You will have to wait until after a couple of fall frosts and follow these simple steps.
- Cut off the dead foliage a few inches above the soil.
- Bring pots indoors and let them dry out.
- 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.
- Store dahlias in dry, cool, dark conditions through winter.
- Inspect the tubers in spring and replant only those that are firm and not desiccated or soft.
FAQs
Q: Will potted dahlias come back every year?
A: Dahlias are regarded as winter-hardy and can grow as perennials in USDA zones 8 and warmer. In cooler climates, dahlias will come back every year if the tubers are correctly overwintered and replanted in spring.
Q: What do dahlias like sun or shade?
A: Dahlias need full sun to thrive. In very hot, sunny climates, plant them in a spot with a little afternoon shade to protect them from excessive heat.
Q: How long do potted dahlias last?
A: If the tubers are properly overwintered, they can last a couple of seasons or more. When overwintering, dig them up or keep them in a pot that’s located in a cool, dry, dark place that won’t freeze. You do not need to water the pot, just let the tubers stay dry as they are dormant.