How to stop or pinch dahlias for bushier plants and more flowers

stopping or topping dahlias

Stopping/topping dahlias, as well as disbudding and deadheading are all techniques that enable us to get the best out of our dahlia plants.

They each have a slightly different purpose but all are ways in which we can influence the production of flowers by the dahlia plant. Here we focus on stopping or topping.

Stopping, topping or pinching out dahlias?

But first, I’ll clear up some terminology issues. There are various ways that this technique is described. In the USA, it is mostly known as topping, pinching, or pinching out dahlias. In the UK, and other parts of the world, the technique is called stopping dahlias.

I tend to use the term ‘stopping’. I guess that is mainly because it is what I am used to. But it is also because I always use the secateurs or snips to do the job as you can see in the video below, rather than simply pinching the stems between thumb and forefinger.

Why do we stop or pinch dahlias?

Stopping or pinching dahlias allows us to create a bushy plant with more blooms. It is carried out earlier in the growth cycle of the plant than disbudding and deadheading.

In order to understand what stopping is all about, it is worth understanding a little bit of the science behind it, so I’ll summarise this below.

As a matter of evolution, any plant’s principal purpose is to regenerate in order to maintain the species. For the most part, this means growing efficiently, flowering and setting seeds. The seeds will be dispersed into the soil, and then germinate and grow into a new plant to repeat the cycle.

How dahlias grow

With dahlias, if left to grow naturally, growing efficiently means the production of a strong main stem that will produce a large, single flower bloom.

At the tip of the growing stem is the growing point – this is technically called the apical meristem. In all plants, the apical meristem leads the growth, producing new leaves and stem sections (or nodes) and, ultimately, the flower(s).

At the junction of each node you will usually find leaves and, between the base of the leaf stalk and the main stem, buds. These are side shoot buds, which are properly called axillary buds.

Growth at the growing point or apical meristem is driven by the production and presence of the hormone auxin. Auxin works by inhibiting the growth of the axillary buds. If the growing point is removed, the production of auxin is stopped and the axillary buds will no longer be inhibited and will then begin to grow – creating new side shoots.

how to stop dahlias
Cut or pinch out the growing points, two or three leaf nodes up the stem

How to stop or pinch dahlias

As you’ve probably realised, the removal of the growing point is what, in the context of dahlias, we call stopping (topping or pinching out). Doing so, encourages the plant to create more shoots branching off from the main stem. This will create a bushier plant, with more flowering stems and, therefore, more flowers.

For garden purposes, you should stop your dahlias once the plant is well established with several pairs of leaves on the main stem. Where you cut depends on how elongated the space is between the nodes on the stem (this is known as the internode).

Cut above the second or third pairs of leaves where the internode is quite large, like the dahlia in the video. Cut at the fourth or fifth leaf node where the internode is small.

You can pinch out the growing point by hand, but it is usually better to use a sharp knife or secateurs, as you can see me doing in the video on this page.

Disinfect your tools between plants, so that there is no risk of disease being spread. It is worth also noting that if your plant puts up multiple stems from soil level, each of those should be stopped.

Once you have removed the growing point, you should see some new stems buds in a few weeks. You can choose to let all the side shoots develop and produce blooms, or you can restrict the number of developing shoots.

stopping dahlias - new shoots

On smaller varieties, it is less important, but on larger varieties, the size of the blooms will be affected by the amount of energy the plant is putting in to growing multiple stems and flowers.

Put simply, the fewer the stems that are allowed to flower, the larger the blooms will be. Conversely, of course, the more flowering stems the plant has, the more flowers it will produce, but the smaller those flowers will be.

Dahlia growers who are aiming to exhibit their flowers will normally restrict their plants to four stems on large cultivars, six stems on medium cultivars and eight stems on small cultivars.

The results

Below is the dahlia I stopped/pinched out in the video, flowering at the end of summer. As you can see, the original two or three spindly stems have multiplied to give a plant with a nice shape and plenty of flowering potential.

Dahlia after stopping/pinching out.

What do you need to stop dahlias?

As indicated above, some people simply pinch out the growing point. So, if you do it that way, you don’t need any tools.

I always use my trusty Felco no 2 secateurs:

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Frequently asked questions

What is stopping or topping dahlias?

Stopping or topping dahlias is a technique that involves removing the growing point of the main stem to encourage the plant to produce more side shoots and flowers.

Why do dahlias need to be stopped?

Dahlias need to be stopped to prevent them from becoming too tall and top-heavy, which can make them prone to wind damage and flopping over. Stopping also creates a more compact and bushy plant with more blooms.

When should I stop my dahlias?

You should stop your dahlias once the plant is well established with several pairs of leaves on the main stem. This is usually done in late spring or early summer, depending on the climate where you live and the variety of dahlia.

How do I stop my dahlias correctly?

You can stop your dahlias by pinching out the growing point by hand, or by using a sharp and clean tool such as a knife or secateurs. You should remove the growing point above the second to fifth pair of leaves. You should also disinfect your tools between plants to avoid spreading diseases.

How does stopping affect the flowering of dahlias?

Stopping delays the first blooms by a few weeks, but increases the number of later flowers. You can ultimately exercise some control over the size and shape of the blooms by choosing the number of side shoots that are allowed to flower.

Stopping will give you more stems, but you in due course can select the best of these and prune out the rest. The fewer the stems, the larger the blooms, and vice versa.

Which types of dahlias benefit more from stopping?

Cactus and decorative dahlias, which have large and showy flowers, benefit more from stopping than single and collarette dahlias, which have smaller and simpler flowers. Stopping also helps to improve the form and symmetry of ball and pompon dahlias, which have spherical flowers.

Can I stop my dahlias more than once?

Yes, you can stop your dahlias more than once if you want to create a very bushy plant with many small flowers. However, this will delay the flowering even more and may reduce the quality of the blooms. It is recommended to stop your dahlias only once for most varieties and where the summer growing season is not especially long.

What should I do with the growing point that I removed?

You can discard the growing point that you removed, or you can use it to propagate new dahlia plants. To do this, you need to dip the cut end in rooting hormone and insert it into moist potting soil. Keep it in a warm humid place until it roots, then transplant it into a larger pot and grow on before planting out into the garden.

More on growing dahlias

You can also get much more guidance on growing dahlias in these posts:

Love Dahlias?I've written the book on them

Check out my comprehensive step by step guide, with plain language explanations and ultra-useful images and illustrations. This is for you if you love dahlias and want to the best out of the dahlias you grow.

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