Horticulture Magazine

How To Deadhead Dahlias

secateurs held horizontally while deadheading spent dahlia blooms

Dahlias are a popular perennial plant that has seen a huge resurgence in recent years and for good reason – they bring a variety of colours to the garden for months on end.

Whether you grow the large and ornate dinner plate or the bountiful single varieties loved by pollinators, all dahlias need deadheading to look their best and grow well.

DifficultyEasy
Equipment RequiredSecateurs or snips, gloves
When To DeadheadJuly, August, September, October, November

Deadheading dahlias can keep them blooming from mid-summer right up until the first frosts, often as late as November here in the United Kingdom.

Imagery and video featured in this article was commissioned by Horticulture.co.uk in collaboration with Organic Gardener Emily Cupit.

Deadheading dahlias is a straight-forward process and should be undertaken from when the first flowers finish onwards:

  1. Identify spent flower heads from the new blooms
  2. Use a sharp implement such as secateurs to remove the spent flower heads

This process is explained in more depth below –

When To Deadhead Dahlias

globe shaped dahlia flower in bloom with dark red petals

Dahlias should be deadheaded as soon as the first flowers finish, which can be as early as July and until they finish flowering at the beginning of winter.

1) Identify Spent Flower Heads From New Buds

yellow secateurs held in hands and shown in front of dahlia plant

The trick to successfully deadheading dahlias is to first identify the spent flower heads from the new flower buds, as once the spent flowers’ petals have finished and dropped, they can look rather similar.

However, there is thankfully a sure-fire way to help differentiate between them.

New flower buds are slightly flat and round, a bit like a miniature satsuma, whereas finished flower heads are cone-shaped and almost pointed.

2) Remove The Spent Flower Heads

hands shown deadheading a potted dahlia plant

Once the spent flower heads have been identified, use a clean and sharp pair of secateurs or snips and cut off the dead flower and its stem just above a leaf or where it joins a main stem.

Otherwise, the flower’s stem will be left in place to die back and look unsightly.

spent pink blooms of a dahlia flower that has wilted

Tiny new buds may be seen just below where the cut is to be made, which will encourage these new buds to burst forth.

To promote continuous flowering, dahlias need to be deadheaded regularly, especially the smaller flowered varieties that produce copious amounts of blooms all at once.

taking the flower head from a dahlia plant with secateurs

Every 2 – 3 days is ideal or once a week at the very least.

Deadheading dahlias for months on end can seem a bit of a chore, especially when planted en masse.

another angle of dahlia plant deadheading

However it’s worth it to have them bloom all season, especially into the autumn when most other perennials have finished, and the spent blooms are perfect for adding to the compost.

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