Our Essential Guide: How to Plant & Pot Up Dahlias

Our Essential Guide: How to Plant & Pot Up Dahlias

Once the overnight frosts come to an end where you are, it'll be time to start thinking about potting up and planting out your Dahlias!

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And so the great unravel and unpacking begins, a little later than anticipated of course. There is always so much to do in the garden and I also have two allotments that in dire need of vegetables. On the allotment I like to grow lots of different things – four different types of cucumbers and beans, two of beetroot, eight of potatoes and five of squash. Taste over yield is key for me and I like to trial things. I can’t tell you the number of dahlias I grow because I honestly don't know.

My dahlia tubers have been sat in their boxes over winter and new boxes have been added, mainly from Peter Nyssen. I also had one sent to me on Valentine’s Day and still have no idea who it is from. It is very pretty though and I am looking forward to planting it.

As you’ll know from my blog a few months ago, I diligently dug the dahlias up, with help from my wonderful father in November, where they then sat in wheelbarrows in the greenhouse. My post shows you what to do if you want to dig up your dahlias and store over winter. I cleaned off the dirt, tidied them up, cut them up, discarded bits I didn’t want, wrapped them in newspaper and stored them in boxes in the frost-free garage.

dahlia tuber snipped and tidy after overwintering
Dahlia tuber unwrapped after overwintering, trimmed and cleaned

Digging up your dahlias isn’t essential, it is purely a personal choice, but given the rain we get here in south Wales, my concern is that they could have rotted in the ground and developed some nasty diseases. I like my tubers to be as clean as possible before I pot them up. I also needed to use the bed for tulips in the spring. In December I planted about 700 tulips, in trenches, and have been selling them locally in mixed bouquets. It’s amazing what you learn isn't it? This year I will be planting my tulips earlier, at the proper suggested time, in an effort to end up with longer stems.


Consider keeping bulbs in the fridge for a cold spell in advance of planting, to initiate longer stems.

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How to pot up Dahlias & how many Dahlias per pot

overwintered dahlias potted up and labelled in April
Dahlia tubers potted up and labelled, showing above the compost

This should be done in March to Early April.

You will need:

  • Clean Dahlias (See if they have any little shoots appearing - these will be your flower stems)
  • A pot for each tuber - 2 and 3 litre pots if you have them (washed and cleaned)
  • Multi-purpose compost (I use a mixture of compost along with soil from their bed)
  • Tools - scissors, hand fork, trowel, gloves, labels, watering can
  • Somewhere to put your dahlia pots, which is frost free (I will be moving mine in and out of the greenhouse in the early stages)
  • Strategy for dealing with slugs and snails (I’m not joking - Dahlias are a veritable smorgasbord for them)


It’s very simple and satisfying.

First select your tuber and find a pot into which it will easily fit and grow. One that is about twice the size is good. Some dahlias have very elongated stems and will need a tall pot. Make sure that the top of the tuber where the shoots are, will sit at or above the soil level - not below.

Make sure that your tuber is nice and clean so with a pair of scissors trim off any straggly hairy roots. Take care not to damage any shoots appearing.

Hold the tuber in the pot and carefully fill with your compost firming gently round the tuber. Add water, label it, and sit in a frost free area.

As the tubers plump up, shoots will appear. Best practice seems to be that if you want strong happy flowering tubers, then you should have no more than five shoots growing off your tuber. First of all, take off any straggly shoots and then the others. As the remaining strong shoots grow, I like to nip (with knife or snips) the tops off the new stems when there are about two or three sets of leaves to promote flowering stems.

Do check regularly for slugs and snails and get rid of them if you can. They can do a lot of damage to tender foliage.

When there is no risk of frost, it will be time to plant out into your borders or pots.

How to Take Cuttings

Taking cuttings is very simple and allows you to make use of any juicy healthy shoots that you took off your potted tuber. Take your healthy shoot and remove all but the top pair of leaves, but keep the full length of the stem in-tact, from tip to base where it joined the main plant. Place the stem into a hole made in a small fresh pot of compost. Make sure that you have stem and leaf nodes in the soil and gently firm them in. Water and leave on a cool window sill, out of direct light. They should root easily, giving you new plants that will develop tubers.

Planting Dahlias In The Garden

Bucket of dahlia bloooms
Bucket of freshly cut dahlias

If you are wanting to plant straight into the ground then you should wait until the risk of frost is over. This will depend on where you are, but is generally considered to be from late April onwards.

You will need:

  • Multi-purpose compost
  • Gravel (if in clay)
  • Tools - fork, spade, gloves, label, tape measure
  • Plant food - pelletised or otherwise (such as Gro-Char, Blood Fish and Bone, 6X)
  • Stake (wood or two or three bamboo canes)
  • Mulch


Dig a hole about 30cm across and 30cm deep. Add some compost to the bottom, and if your soil is clay, add a handful or two of grit. Water well.

Place your dahlia tuber in the hole, and position, so that any shoots or the base of the flower stem are at or just above the top of the soil. Fill in with the compost. Firm the soil and water well.

The stake should be positioned next to the tuber at the same time to avoid damage. Use the bamboo canes around the plant.

Water well and wait for shoots to start appearing. As with the earlier potting you don’t need more than five shoots for a strong flowering plant. So take them off and use the stronger ones as cuttings. Also nip the tops off the shoots when there are about three sets of leaves.

If you are growing a number of dahlias, space them about 45cm to 60cm apart, depending on their size and requirements. As I am looking to grow for cutting and use smaller tubers to start with, I will be planting at about 45cm apart, although this may change.

Commence with a first feed 1-3 weeks after planting and thereafter every three weeks or so. I also like to cover and raddle in a ground mulch from my garden compost bin, around each plant, but not touching.

As the dahlia grows, tie in the stems. When cutting stems for the vase, dahlia flowers needs to be pretty much in full flower. I cut and immediately place into a bucket of water and leave in a cool place for a couple of hours or overnight for a good drink and conditioning prior to use. If you aren’t cutting flowers for use then they will definitely need regular deadheading. Don’t leave any finished flowers on the plant, unless you are looking for seeds. Dahlias are great cross pollinators.

Watering is important for dahlias and is best done early in the morning as they need a good flood to stop those starchy tubers stressing and drying out (did you know they are edible?). Try to avoid watering in the evening as the slugs love a wet night - it’s like the best party ever for them. This year I’m going to lay a leaky hose and do some gradual watering in the early morning.

Growing Your Dahlias In Pots

Dahlias in full flower look amazing in pots and worth doing if you don’t have garden space although you will need to be more assiduous about watering.

Use a pot about 30cm wide and 30cm deep with good compost. And don't forget to nip the tips, feed, water, cut stems and deadhead.

Here’s to some very happy dahlia days.

Field of Dahlias

Field of Dahlias

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