What to do with dahlias in June – 4 expert-approved ways to kickstart this year's flowers

Our dahlia plants are set to burst into bloom from next month, which is why this month is such a crucial one in the calendar. If you want them to flower right through to the autumn, you’ll need to know what to do with dahlias in June.

Whether you’re growing dahlias in pots or garden borders, they’ll need some extra TLC in the lead-up to their flowering period. That means planting them out before the window closes, offering them plenty of support, and a few other crucial tasks that will have them putting on their best displays.

Here’s a list of things to do with dahlias in June to get you started.

Latest Videos From

Watch full video here:

What you'll need

1. Plant them outside

If you potted up your dahlias (kudos if you did – it’s one of gardening expert and author Sarah Raven’s golden rules for growing dahlias) and haven’t planted them out yet, June is your last chance to move them outside.

‘If you haven't already done so, now is the time to plant out any remaining tubers or potted plants,’ says Jane Westoby, creative director at The Hampshire Seed Company. ‘At planting time, enrich the soil with organic matter and a slow-release fertiliser such as fish, blood and bone and a sprinkle of chicken manure pellets.’

You can order an 8kg bucket of Westland Organic Chicken Manure Pellets from Amazon.

'Plant them in fertile, well-drained soil, making sure the tubers are completely covered, along with the lower part of the stem,' adds Sarah Raven. 'This adds stability as the dahlia grows and stops the tubers from drying out in hotter summers. Mulch with compost and space them around 75cm apart.'

2. Know when to water them

If you’re wondering what to do with dahlias in June, your watering schedule could make all the difference to their health. Young dahlias are thirsty plants, so you’ll need to be extra attentive with the watering can at this time of the year.

‘Newly planted dahlias will need more frequent watering while they establish, particularly during hot or dry weather,’ explains Jane.

After the plants are settled in your garden, it’s quality over quantity.

‘Once established, I prefer to water deeply rather than little and often, encouraging roots to grow down into the soil,’ says Jane. ‘The exact frequency depends on your soil type and weather conditions, but a thorough soak once a week is usually better than a daily sprinkle.’

Jane also notes that container-grown dahlias will need more regular watering, even every day during warm spells. Just don't overdo it on cooler days – overwatering can cause dahlia leaves to turn yellow.

3. Offer them support

Many dahlia varieties grow tall, and when you pair that height with the huge blooms on some of the dinnerplate types, they can quickly become too big for their boots after flowering begins. That’s why you’ll need some of the best plant supports to hand before they burst into bloom.

‘In June, tall-growing plants like dahlias put on vigorous growth and can become top-heavy once they bloom,’ explains Paul Parker from perennials and annuals specialists J. Parker's.

‘This is why staking these plants now will help keep stems neat and protect them from sudden summer storms.’

This double ring dahlia plant support from Crocus is made from uncoated steel and can develop a rust effect.

4. Feed them

It's also a good idea to start feeding your dahlias in June to encourage strong plants and plenty of flowers.

'I suggest using a slow-release fertiliser or feeding dahlias in pots every fortnight with a liquid comfrey or seaweed fertiliser,' says Sarah. 'If you’ve used a slow-release fertiliser, there is no need to feed.'

The Shropshire Seaweed Company Organic Seaweed, which you can order from Amazon, is a certified organic plant food which promotes growth and enhances soil health. Just make sure you don't overfeed your dahlias, since that's one of the leading causes of dahlias not blooming.

If you're growing dahlias, add these tasks to your list of June garden jobs to encourage showstopping blooms.