How to deadhead dahlias – for a healthy, long-term show

Undeniable stars of the flower bed, knowing how to deadhead dahlias is crucial for keeping these showy and flamboyant blooms flowering.

There is such a wide variety of dahlias to enjoy that they can have a lead role in the late season garden flower bed ideas. Choose from the array of colors, varying flower sizes and shapes, multi-colored blooms or dark foliage cultivars. Growers across the world continue to introduce further variations and combinations to keep up with the trends – in fact, the range of sizes and colors is practically unmatched in the world of flowers. With the right care and attention, dahlias can keep flowering from summer into winter.

Once you learn how to grow dahlias, you'll soon become obsessed with them after  you witness the first blooms unfurl. So to keep dahlias blooming for longer, read on to find out how to deadhead dahlias and when.

How to deadhead dahlias

If you're new to dahlia growing, you will first have learned when to plant dahlias for the best results, and mastered step by step how to plant dahlia tubers. Once your blooms start to appear in mid summer, it's then time to learn how to deadhead dahlias.

Dahlias make wonderful cut-and-come-again blooms if you're planning a cut flower garden because they flower for months on end. Deadheading and picking these invaluable late summer flowers regularly encourages them to keep producing more flowers right up to the first frosts. 

As with deadheading or pruning any flowers, make sure you have the correct equipment to hand so as to avoid damaging the plants. 'You will need a sharp knife or pruning shears to deadhead dahlias,' explains Tye Abdul, CEO of Abdo Florist.

What is deadheading?

Deadheading dahlias involves only removing the spent flower buds. This does not harm the plant, but instead, by removing the dying blooms, you encourage the plant to put its energy into root and flower development.

'Unless you’re leaving seedpods to mature on the plants for breeding purposes or collecting seeds, be sure to remove any spent blooms so that the plants continue to put energy into flower production rather than making seeds. This practice is an important ritual in the cutting garden if you want a steady stream of beautiful blooms for the longest amount of time, ' explains Erin Benzakein, author of Floret's Farm's Discovering Dahlias.

Where do you cut when deadheading dahlias?

Where you cut when deadheading dahlias is important.

Once your dahlias begin to bloom, then Inspect the flowers at least once a week to check if there are any dead or dying flowers. You want to remove flowers as they begin to wilt and any that have completely wilted and are beginning to form seed pods.

You'll soon find when learning how to deadhead dahlias that it's easy to identify spent blooms where the petals are wilting and starting to fall off. But if you miss that stage, it isn't always as easy to identify which buds you should deadhead and which are on their way to producing blooms.

'It can be tricky to tell spent buds from new ones sometimes – the key is in the bud shape. If it’s pointed – and a bit squishy – it has gone over; if it is round and perky, it is a new bud,' explains Pippa Blenkinsopp, Homes & Gardens Content Editor, and an expert in growing dahlias in her beautiful cutting flower garden.

After you’ve identified which flowers are wilting or buds you need to deadhead, then using a pruner, cut the flower stem as its intersection to a leaf. This will promote more blooms and avoid the sight of flowerless stems sticking out all over the place.

Where do you deadhead dahlias if a stem has more than one bloom?

'The tricky part of deadheading dahlias is when there are multiple heads on one stem. If one of the flowers has gone over you have two choices: you can either take off the dead flower by cutting back to the bud joint, leaving the other buds to bloom, or, you can make the decision to cut further back down the stem at the next set of leaves,' explains Pippa.

'If the flower stems are short, I often tend to cut the dahlia back further down the stem to encourage longer new shoots for cutting to create a summer flower display. Having one of the short flowers cut off from a three-headed flower stem might not look great in a vase. But if you are growing dahlias for color in the border for garden color schemes, then this may not be an issue,’ she adds.

When should I deadhead dahlias?

When you should deadhead dahlias will depend on when they start blooming, which will differ depending on the hardiness zone where you live.

'It helps if you deadheaded dahlias every few weeks to keep them blooming,' explains Tye Abdul, although in high season this can increase to every few days.

You need to deadhead dahlia flowers once they have wilted and the buds are spent.

How do I keep my dahlia blooming?

The best way to keep your dahlia blooming is to deadhead spent blooms regularly, and also cutting flowers for floral displays around the house, which will encourage your plants to produce more blooms.

'Like any plants, dahlias are prone to bacterial, viral, and fungal diseases when stressed,' explains Erin Benzakein, so make sure you keep your plants happy and healthy, by planting in the right spot, allowing lots of airflow and caring for and watering them correctly. Where you do encounter pests or diseases, 'I advise using organic methods as much as possible. Growing naturally takes more effort and attention, but pays off in the quality of the flowers,' Erin adds.

Deadheading, however, is one of the most crucial elements in keeping your dahlias blooming for longer.