How To Plant & Pot Dahlias

4 October 2022 | Matt

pink dahlia

When frosty nights turn warmer, the time has come for dahlia planting and potting plans.

So, the sorting out commences somewhat later than anticipated, as there are always so many gardening tasks to complete, especially if you have multiple allotments or a large garden in desperate need of vegetables.

You can actually dig up and store dahlias over winter, by tidying them up and removing the dirt, cutting off the waste parts, and placing them in boxes wrapped in newspaper stored in the garage.

If you’re planting dahlia bulbs, keep them refrigerated before planting, as this will encourage longer stems.

How To Pot Dahlias

Dahlias should be potted between March and early April, so getting organised is essential.

Steps to do before starting:

Scissors, trowel, small garden fork, labels, gloves, and a watering can.
Clean Dahlias - Look for new shoots - these are the stems.
One pot per tuber - Pots should be clean and two to three litres.
Multi-purpose compost - You can mix compost with soil from the bed.
A frost-free area for the potted dahlias - change between in or out of the greenhouse at first.
Control of slugs and snails – they love dahlias, so you need to protect them.

Steps to pot Dahlias:

Select a suitable fitting pot where your tuber will grow. Your pot should be about twice the size. Dahlias with elongated stems need tall pots. Make sure the new shoots remain above the soil line.
Trim any hair-like or dishevelled roots with scissors. Take care to avoid any new shoots.
Suspend the tuber in the pot and fill it with the compost with gentle pressure on the surrounding area. Water it, label and place it in your frost-free area.
As the tubers become fleshy, new shoots will appear. The optimal number of projections is no more than five to have happy, solid and flowering tubers. Take off any wayward or excessive shoots. To promote flowering, remove the tops of new stems once they have two or three sets of leaves with a knife or snip.
Remove slugs and snails often. They will cause lots of damage to the young growth
Once there is no longer any risk of frost, plant outside into your borders or pots.

white and pink dahlia

How To Take Dahlia Cuttings

It's easy to take cuttings. Juicy, healthy shoots taken from your potted tuber are favourable. Remove all the leaves leaving the top pair whilst keeping the length of the stem intact. Make a hole in a small pot of fresh compost and place the stem inside. Make sure to firm the stem and leaf nodes gently. Water it and put it on a cool windowsill away from direct sunlight. It should root easily, creating a new plant which will develop a tuber.

How To Plant Dahlias In Your Garden

Should you wish to plant straight into the ground, wait until the risk of frost has passed. Depending on location, this is generally from late April onwards.

Steps to do before starting:

Fork, gloves, shovel, tape measure, and a label.
Stakes of canes
Multi-purpose compost
Gravel – useful for clay soil.
Plant food
Mulch

Steps to plant Dahlias in the garden:

Dig a 30 x 30 cm hole and cover the bottom with compost. For clay soil, add a handful of grit. Then water abundantly.
Position the dahlia tuber in the hole, ensuring the shoots and base of the stem are just above the soil level. Fill with compost and firm the surrounding soil. Give it plenty of water.
At the same time, position the stake next to the tuber to prevent damage and place the bamboo canes around the plant.
Give plenty of water and wait for new shoots to appear. As previously mentioned, five shoots are optimal for a good flowering plant. Remove any excess shoots, the stronger of which may you can keep as cuttings. Take off the tops once approximately three sets of leaves appear
Dahlias should be placed about 45 cm to 60 cm apart according to size and need. I use smaller tubers to start with to grow for cuttings, and these will be 45 cm apart approximately; however, I may alter this distance.
Feeding should begin one to three weeks later and continue every three weeks from then on. I usually surround each plant without touching it with mulch from my garden compost.
Tie the stems in once growth becomes established. Dahlias should be in full flower before taking cuts for the vase. Place into a bucket of water immediately after cutting and leave overnight, or, at least, a couple of hours to take in enough water for condition before use. If not cut, flowers will need to be frequent deadheading. Unless the seeds are wanted, don't leave finished flowers as dahlias will cross-pollinate.
Dahlias are best when watered in the early morning. Starchy tubers must be drenched with water to prevent them from becoming stressed and drying out. (They are edible). As slugs are nocturnal and love the wet (Party time for them), avoid watering in the evening. This year, I will lay a leaky hose in favour of gradual early morning watering.

Growing Potted Dahlias

Potted dahlias in full bloom look fantastic and are well worth the effort, especially if you lack space in the garden, although diligent watering is necessary.

30 x 30 cm pots are helpful with good quality compost. Remove the tips, feed, water, cut stems and regular deadheading.

Browse our related growing content here:

Conclusion

We hope you enjoyed our article on how to pot and plant dahlias.

If you have any questions, leave them in the comments, or email info@swgreenhouses.co.uk.