Growing Dahlias in Pots and Patio Containers

March is delivery time for dahlia tubers, which are too tender to plant out any earlier in most of the UK, apart from the mildest coastal South.
Because it’s still too cold in most areas to plant them out until April, the best thing to do is pot them up and store them somewhere frost free, then plant them out later.
That way, you are sure to get your varieties of choice before someone else does, and then your darlings get off to a dashing start in your border.

So, an obvious question arises: are Dahlias suitable for pots? Why bother planting them out at all?

With a bit of planning and attention to ensure their success, your patio can be a real Dahlia display in the style of Claus Dalby’s, here lavishly presented by the Middle Sized Garden:

Note that Claus is in Denmark where Spring warms up a bit later than the UK, so he starts his Dahlias in pots at the start of April – we like to start anytime in March

Which Dahlia Variety Will Suit My Pot?

Your first consideration is the type of dahlia: the larger the variety, the larger the container needs to be.
Large dahlias (many of which are known as “dinner plates”) in a small pot will look out of proportion, become top-heavy, and could even topple over in the wind!
Small dahlias in a really large pot will probably also look out of proportion, and it’s using up more compost, water, and fertiliser than necessary (with that said, big pots also dry out slower in mid-summer when you want a weekend away).

What Size Pot do I Need for Growing Dahlias?

Even dwarf cultivars will require a 30cm (about 10 litres) pot.
Dwarf cultivars are probably the easiest choice for containers, but when paired with an appropriately sized pot, then a mid-size Dahlia will be absolutely fine.

If you happen to have very large containers then why not give a giant dinner plate Dahlia a go?

Sturdy Supports:

No matter what the Dahlia, you will have to provide strong supports up to the mature height of your cultivar, and this can be done in various ways.

Claus has the best Dahlia support rings we’ve ever seen or dreamt of, so we skipped to the end of this video for you to see them.
The trick is that they are sturdy, rusted metal, which blends well with the foliage, and they are a generous sized open ring (no grid in the middle), so the Dahlia can move in the breeze, rather than looking all trussed up.


At the height of summer, Dahlias become heavily laden with leaves and blooms and thus require a good deal of water. This is less true in the spring when they are first becoming established. Ordinarily, overwatering during this time should be avoided, but in the case of containers, this is not necessarily the case. Pots have a tendency to dry out quickly depending on a few variables – the type of pot, the potting mix, the pot’s position, the strength of the sun, and the drying effects of the wind, to name a few – so be sure to monitor your pots and adjust your irrigation schedule accordingly. Be prepared to water them more regularly than you may be used to when planted out directly in your garden. This will certainly become a regular chore in the summer months.


Use a well-draining potting mix enriched with organic matter to promote healthy growth. Mulching the surface of the potting mix will help retain moisture and regulate soil temperature.


As with all container planting, an important factor is a feeding schedule. When we plant in rich garden soil, full of organic matter, microorganisms, and plant nutrients, we can often get away without supplementing with fertilizers and still yield a satisfactory result. Be aware that this is not the case with container planting – after the first approximately 6 weeks of growth, that sterilized potting compost is completely spent, and the Dahlia will be almost fully dependent on your supplemental feeding schedule.

Dahlias will require a balanced NPK feed of 10:10:10 during the first stage of establishing. But once they start to flower, it is important to switch to a potassium-rich fertilizer applied as a root drench approximately twice a week at a minimum. If time allows, then a pro-tip here applies equally well to dahlias in containers as they do to, say, growing tomatoes in bags. Double the frequency of the liquid feeding (therefore weekly in this case), but half the dilution rate of your mix. This will ensure a more regular availability of plant nutrients while avoiding the risk of over-applying fertilizer. While liquid feeding is probably the best approach, not all of us have time to do this with regularity. In this case, it is well worth considering a slow-release granular fertilizer (article link – advice fertilizers)

Pruning and Deadheading:

Maintaining the vigour of your potted Dahlias calls for pruning and deadheading.

Pinching back the tips of young Dahlias when they reach around 15-20 cm in height encourages fuller, bushier growth. This technique should be repeated throughout the growing season, especially for the larger varieties.

Deadheading is absolutely essential, and you don’t need to be precious about this, just cut above the first set of leaves to keep things neat and redirect energy for new blooms.

Regular deadheading prevents seed formation, making your Dahlias bloom longer and as the season rolls on, consider giving the entire plant a trim to stimulate a fresh set of blooms.
For taller Dahlias, a trim of about one-third of the main stem height works well.

Try to make sure you have a regular deadheading schedule, especially when flowers are in full flow and if you are short on time, just prune them out when individual flowers start to fade- if you wait then it can be a chore to distinguish new buds from spent ones.

Key Takeaway

Dahlias can thrive in pots just as they do in the ground, but you have to be vigilant with watering, feeding, and it’s best to choose a cultivar that suits the size of your pot.

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