Dahlias can be grown in three ways; from tubers, rooted cuttings and seed. Dahlia tubers are the roots of mature dahlias, and look like a cluster of brown, carrot-like roots joined by the previous year’s dried stem.
When to plant
A great way to get dahlias growing earlier in the season is by starting them in pots in March or early-April. Starting dahlias in pots also encourages them to develop quickly, icreasing the likeliness of them flowering early. When all risk of frost has passed, they can then start to be hardened off and planted outdoors.
Step-by-step guide to planting Dahlia tubers
- Dahlia tubers
- Large pots
- Peat-free multi-purpose compost
- Plant labels (optional)
- Pen (optional)
- Pruning snips/ sharp scissors
- Garden hand trowel
- Well-rotted organic matter
- Horticultural grit (optional)
- Stout stake or bamboo canes
- Slow-release plant food (optional)
1 – Starting in pots
If you want to grow dahlias early, you can start by planting their tubers in big pots filled with peat-free multi-purpose compost in March or early April. But before you do that, soak the tubers in a bucket of warm water for an hour. This will help them get enough water. When you plant them, make sure the joint where the roots meet the stem is facing up. This is important. Then, label the pot so you know which one has dahlias in it, and put it on a windowsill or in a frost-free greenhouse. And don’t forget to water the tubers regularly.
2 – Staring to grow
When you notice the tuber has started to grow, you can start pinching off the tips of the main shoot all the way down to the top pair of leaves. You should also remove most of the other shoots growing from the tuber, leaving only five. This helps the plants become bushy and grow strong and healthy. As a result, you’ll get a lot more flowers.
3 – Hardening off
After the frost risk has passed, it’s time to harden off your dahlias. This means you should gradually get them used to being outside. You can start by putting them outside during the day and bringing them back in at night. Do this for a week, and then they’ll be ready to be planted in their final spots where they’ll grow.
4 – Planting in the garden
You can plant your dahlias in the garden in mid to late May, once you’re sure there won’t be any more frosts. But before you do that, remove some shoots from the tuber, leaving around five remaining. This will help the plants become bushy and produce lots of flowers.
When planting, dig a hole at the same depth the plant was in the pot. Then, add a bucket of well-rotted organic matter to the soil to make it more fertile. If your soil is heavy clay, you can add some horticultural grit to the base of the planting hole to improve drainage. Dahlias like a lot of room to grow, so make sure to plant them about 60cm apart.
5 – Adding supports
Dahlias grow quickly and may start to droop, especially if their flower heads are large. To prevent this, you can add a sturdy stake or bamboo canes at each corner of the plant (don’t worry, they’ll be hidden as the plant grows). Then, tie the new growth to the stakes every couple of weeks to keep the plant upright and well-supported.
6 – Planting in containers
If you want to grow dahlias in a container, choose a big one that’s at least 30cm wide and deep. Fill it up with multipurpose compost mixed with organic matter, such as well-rotted manure. You can also add some slow-release plant food to the mix. When planting the dahlias, make sure to plant them at the same depth as they were in their original pot.
Caring for Dahlias
At the point when your dahlia plant has developed to around 20cm tall, you can support more blossoms by squeezing out the super developing tip. Using a sharp knife or your thumb and forefinger, cut the main shoot in the center of the plant, which is growing upright, down to the top pair of leaves. Then, every few weeks or so, connect fresh growth to the stake.
Every two weeks, give your dahlias a high potash feed, such as tomato feed, to keep the flowers coming. Make sure to water them well once a week too.
It’s important to deadhead your dahlias regularly to extend the flowering season. To do this, remove the whole flowering stem, making sure to distinguish between buds (round) and spent flower heads (pointed).
Dahlias may not survive in very frosty or wet conditions during winter. To keep them safe, it’s best to lift the tubers once the foliage has been blackened by frost. First, cut the stems back to about 12cm. After that, use a garden fork to gently lift the tuber and remove the soil with your fingers. Place the tubers upside down in a tray lined with newspaper, and let them dry out for a couple of weeks in a dry place.
After the tubers have dried out, place them in a cool, frost-free place in a shallow tray of dry compost or horticultural sand. Do not water them and they do not need light during this time. When it’s time to pot them up again, keep them there until late March or early spring.
On the off chance that you live in a space with gentle winters and very much depleted soil, or on the other hand in the event that you don’t have the space to lift and store dahlia tubers, you can cover the dirt with a thick layer of mushroom manure or potentially straw to keep ice from entering the tubers. In the spring, essentially rake away the overabundance manure.
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