Pinching Out Dahlias Early Can Change Everything

An early, radical cut can change everything.

Anyone who loves dahlias will know the problem: the plants shoot upwards, the foliage looks impressive, yet only a few flowers appear in the end and the long stems topple in the first strong gust of wind. Garden professionals therefore use a technique that initially seems harsh: they simply remove young, healthy shoots – and can often get three to four times as many blooms from the same plant.

Why an early cut makes young dahlias stronger

Left untreated, a dahlia follows its natural hierarchy: one dominant main shoot grows upwards, taking most of the plant’s energy and allowing only a few side shoots to develop. The result is tall, leggy growth, fewer flowers and an unstable plant.

Early intervention changes this completely. Once the dahlia is around 20 to 30 centimetres tall and has four to five pairs of true leaves, the tip of the main shoot is removed. This small action overturns the plant’s internal “power structure”.

A young shoot pinched out early forces the dahlia to produce several strong side shoots – one flowering axis becomes four to six.

Plant trials at major gardening institutes show that dahlias pinched out while young produce considerably more flowering stems over the season. Rather than becoming a thin pole carrying just a few large flowers, the plant branches out, stays more compact and develops greater stability.

There is a trade-off: the first flowers usually open 10 to 15 days later than on uncut plants. Across the whole season, however, home gardeners gain significantly more: instead of a handful of spectacular blooms, they get a genuine cloud of flowers that is easier to cut and use in bouquets.

What happens inside the plant during so-called “pinching out”

There is a clear botanical process behind it. The tip of the main shoot produces the plant hormone auxin. This hormone favours growth of the leading shoot while suppressing lateral buds. Specialists call this “apical dominance”.

When the shoot tip is removed, auxin production at that point stops abruptly. The buds in the leaf axils, previously held back, become active and start growing. Rather than one stem, several vigorous side shoots suddenly develop, all of which will later carry flowers.

In practical garden terms, this means more potential flowering points, more evenly distributed weight and a plant that is less likely to snap or bend over. Large-flowered varieties benefit particularly strongly, as their heavy flower heads need a sturdy framework to support them.

The ideal time: when dahlias should be pinched out

Getting the timing right determines whether the plant benefits or suffers. Gardeners should not follow a calendar date, but instead assess the dahlia’s stage of development.

• Plant height: around 20–30 centimetres
• Present: 4–5 pairs of fully developed true leaves
• Stem: still comparatively thin, green and solid rather than hollow
• Weather: a dry day, with no rain expected

In most areas, this stage arrives roughly three to four weeks after planting the tubers, depending on soil temperature and weather conditions. Dahlias started in pots often reach this point sooner in a warm greenhouse or on a windowsill.

How home gardeners pinch out dahlias step by step

The technique itself is straightforward, but it requires precision. Cutting too low removes unnecessary plant material, while cutting too late can even put the tuber at risk.

Tools and preparation

Some gardeners use only their fingers, while others prefer tools. Either method works provided it is carried out cleanly.

• Small, sharp secateurs or nail scissors
• Disinfectant, such as 70% alcohol
• Disposable gloves, if needed, to prevent the spread of disease organisms

Before every cut, wipe the cutting surface of the scissors briefly with alcohol. This prevents fungal spores or bacteria from entering the fresh wound.

Making the cut

First, locate the central main shoot. On this shoot, count the fully developed pairs of leaves upwards.

• Find the second or third well-developed pair of leaves.
• Position the cut directly above that leaf pair.
• Remove the tip with a clean, straight cut.

Gardeners with practised fingers can simply pinch off the tip between thumb and forefinger. The plant will pause slightly over the next few days before new side shoots gradually become visible.

Do not cut too low: the upper leaf pairs remain as the plant’s engine, supplying energy for new branching.

These cutting mistakes can put dahlias at risk

The most common mistake is poor timing: many home gardeners only reach for the scissors once the dahlia already looks very vigorous. By then, it is usually too late.

As soon as the shoot reaches a diameter of around one centimetre, its centre becomes hollow. Cutting at this stage creates a kind of small chimney. Rainwater can collect in the opening, slowly travel downwards and cause the tuber to rot within a few days.

Anyone who has missed this window should avoid cutting and support the plant instead. A sturdy cane and several soft ties will then save far more than a late intervention with scissors.

Further common pitfalls

• Cutting too low: If there are hardly any leaves left above the cut, the plant later lacks the “solar panel area” needed for fresh growth.
• Wet weather: Cutting during rain gives fungi an easy route into the plant.
• Dirty tools: Bacteria can enter the conducting tissue directly through the cut surface.
• Weak plants: Dahlias that are unhealthy or weakened by slugs should first be allowed to regain strength.

When cutting is worthwhile – and when it is not

Not every dahlia responds to the same degree. Large-flowered varieties for beds and borders benefit most clearly. With these plants, dense colour impact is usually the priority rather than record-breaking diameter in individual flowers.

Anyone aiming to grow enormous individual blooms, for example for exhibitions, sometimes does the opposite: side shoots are removed and only a few flowers are retained so that all the plant’s energy goes into those flower heads. For an ordinary home garden where cut flowers are wanted, pinching out young plants is considerably more useful.

Garden aim	Recommended technique
Many flowers for beds and bouquets	Pinch out early at a height of 20–30 cm
Few, very large exhibition blooms	Leave the main shoot, limit side shoots
Weak-growing or diseased plants	Stabilise first, cut very little

Care after cutting: getting the most from your dahlias

After the intervention, it is worth paying close attention to the soil and nutrients. The plant needs energy and consistent conditions to produce many new shoots.

• Water to keep the soil lightly moist, but never waterlogged
• Apply a mulch layer of grass clippings or leaves to prevent drying out
• Feed moderately, ideally with an organic flower fertiliser
• Secure exposed, windy positions with canes or support frames

Once the new side shoots start to form buds, particularly weak shoots can be selectively removed once more. This directs more energy into the remaining, stronger stems.

Why having the confidence to cut early pays off

Many home gardeners hesitate to cut into a seemingly healthy, vigorous young plant. The instinct is understandable: nobody wants to “damage” it. Yet those who take the step will usually experience the opposite – the dahlia later looks far more impressive, flowers for longer and is less likely to fall over.

The method also offers a useful opportunity to become familiar with plant physiology. You can see directly how powerfully a single cut affects shape, stability and flower production. Anyone who has watched pinched-out and unpinched dahlias diverge so markedly side by side will usually not want to be without the trick the following year.

For beginners, it is worth treating only some of the plants this way at first. This creates a small practical experiment in your own garden, more illustrative than any theory – and ideally results in a summer in which dahlia beds and flower vases are noticeably fuller than in previous years.