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How to grow Dahlias in pots

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How to grow Dahlias in pots
Photo by Timo C. Dinger on Unsplash

While dahlias are commonly planted in outdoor grounds flowering beds, it is possible and beneficial to grow these stunning flowers in pots or any other suitable container. But as with any plant, there are things to be aware of before you start your propagation project! To plant dahlias in a pot, use a big container that’s 30cm wide and deep. Fill it with multipurpose compost and organic matter like well rotted manure.

Many people call planting dahlias in pots as balcony dahlias, because they can be planted in a small sized pot, so they can be fitted even on a compact, balcony. First things first! Be mindful when picking your dahlia variety – some are bigger than others. So, a Dinnerplate Dahlia that grows up to 5 feet might not be suitable for the 12-inch pot you have waiting at home. And, of course, learn about the proper care and maintenance of the plant. The depth depends on the species of dahlia you are growing. The roots of a taller plant can grow as deep as 6 to 7 inches, while shorter varieties produce roots of 2 to 3 inches.

What does planting in pots mean?

Planting in pots means that instead of planting the plant in the ground, you are using a pot to plant directly inside them. This planting method is efficient, when you don’t want to mess up your garden or you don’t have enough space and pots can defend the plants against pets.

When should you plant in pots?

You should plant in pots when you don’t have space to plant in the ground. If you live in a flat, you won’t have a garden with grass, so you want to have you plants inside the flat. In addition, if you have a pet and you want to defend the plants from them, you cannot have you plants in the ground, because without a proper fence, the plants will be destroyed eventually. You can use better potting mix than you ground might be, so the plant will grow more effieciently.

How to grow potted dahlias from tubers?

Like we said, first choose your desired dahlia variety. Smaller and medium-sized flowers perform well in a pot of 12-inch diameter and 12 inches depth. It’s not impossible to grow bigger species in container, either. The key is to use a heavy pot – dahlias can weigh quite a bit. The most common way for starting dahlias is with the use of dahlia tubers.

Dahlia tubers, sometimes called bulbs, are clumps growing under the soil. You can find them at most garden centers for a reasonable price. If you want to start your dahlias outdoors, wait until the last frost has passed before planting dahlia tubers. However, you can get a head start by planting the dahlia tubers in pots and keeping them indoors until late May/early June.

  1. Use a peat-free, all-purpose well-draining potting mix. A good tip is to mix some fertilizer in your soil.
  2. Put a bit of the potting mix on the bottom of your pot and mold it into a hill. 
  3. Balance your tuber on the soil with its central stem pointing upwards.
  4. Fill the rest of the container with soil, lightly tapping it to break any air pockets. The planted dahlia tubers should be fully under the ground.
  5. Water the planted tuber, and don’t water again before the dahlia tubers sprout.
  6. It takes 2 to 3 weeks for the shoots to appear. Once the shoots have grown a bit bigger, pinch down the tips of the main shoot.
  7. (Optional). Remove some of the stems from the soil leaving around five. This allows the stems remaining in the container to get more nutrients and energy, resulting in many flowers.

When growing dahlias indoors, it’s a good idea to use the help of artificial lights. Dahlias want a lot of light, and getting full sun indoors can be challenging.

How to grow potted dahlias from seeds?

As we just mentioned, dahlias are generally grown from dahlia tubers, as this is the most reliable way to go about it. But it is certainly not the only way to do it! It is possible to grow dahlias from seed. This is a perfect method for those who don’t already have a parent plant to take dahlia tubers from. So, how exactly do you grow dahlias from seed?

  1. Fill a container or seedling tray with moist compost and lightly tap the surface to firm the potting soil.
  2. Sow your dahlia seeds.
  3. (Optional). Cover with a plastic bag or a lid. Indicating a greenhouse effect will potentially speed up the germination process.
  4. Germination generally takes around two weeks. You’ll know your dahlia has germinated when it sprouts. Gardeners often call those sprouts true leaves.
  5. Transplant your seedlings into individual plants. Make sure you use peat-free compost and water well.
  6. Around mid-May, start hardening off the plants by leaving them outside during the day. Don’t leave the plants out during the night before the last frost has passed. Unless you want your plant to die.

Care for potted dahlias

Dahlias thrive in a soil that is consistently moist. During periods of drought, it is recommended to water them once a week with a generous amount of water, rather than a light sprinkle. For potted dahlias, frequent watering is necessary, especially during dry spells, with a daily watering routine being ideal. These plants have a high water requirement.

How much water do dahlias need?

After the dahlia has been planted, it should not be watered as this is when the root system is developing. Watering should only be started when the first green sprouts appear on the surface.

How much light do dahlias need?

Dahlias like warm temperatures and full sun, but not full heat and drought. It will be fine if you leave it outside in full sun for a day, but after that, find a slightly cooler place out of direct sunlight to avoid burning the leaves.

Can dahlias overwinter?

Yes, dahlias can overwinter in container by saving the tubers. At the first frost in autumn, you may notice that the plant is not in good condition, with a rapid weakening. It is then necessary to start preparing the dahlia for overwintering.

How to prepare dahlias to overwinter?

Separate the stem and tubers first. Afterwards, the rotten parts should be examined and cut off. Treat the tuber with antibacterial disinfectants. Hang it on a string in a cool, dry and well-ventilated room and protect it from direct light. Wait until spring when there are no more frosts and replant the tubers in the ground.