Preparing Dahlias for a Local Flower Show

Late August and early September are when dahlias come into their own, just as village shows and horticultural society autumn events fill the marquees with colour. A little quiet preparation in the days beforehand is the difference between a stem that catches a judge's eye and one that quietly fades on the bench. Judges score on four things above all: condition, form, colour and uniformity. Everything below is aimed at those four.

Start with the Schedule, Not the Plants

Before you cut a single stem, read the show schedule properly. It tells you far more than the date and the venue.

• Class definitions. A class asking for "three blooms, one cultivar" is judged on uniformity, so all three must come from the same plant or, at least, the same variety grown under the same conditions. "One vase of dahlias, mixed" is a very different task.
• Numbers and vases. Some shows supply vases and staging rings; others expect you to bring your own. Check whether the class asks for one bloom, three, or five, and whether foliage is permitted.
• Naming. Many classes require the cultivar name on a label. Write it clearly and legibly — "Bishop of Llandaff" rather than "red one".
• Staging times. Note when you must have your entry on the bench, and work backwards from there.

Deadhead and Disbud Through the Season

Show-quality blooms are made weeks in advance. Deadhead every two or three days, cutting spent flowers back to a strong pair of leaves rather than snapping the head off. This stops the plant pouring energy into seed and keeps a steady supply of fresh buds coming.

For large decorative, semi-cactus and cactus types, disbudding is the trick that produces a single big bloom per stem. Remove the two side buds either side of the central one while they are still small, leaving one flower to develop without competition. For pompons, ball dahlias and the smaller bedding types, leave the sprays alone — uniformity across a spray is what earns points there.

Feed sensibly. A high-potassium tomato feed from midsummer onwards hardens stems and deepens colour. Too much nitrogen late in the season gives you floppy stems and soft, short-lived petals.

Support Stems and Shield Blooms

A bent neck is one of the most common reasons a lovely dahlia loses marks, and it is entirely avoidable. Stake each plant early with a cane and tie it in with soft twine in a figure-of-eight, so the stem is held but never pinched. Check ties after wind.

British weather being what it is, some protection pays. If heavy rain is forecast, slip a paper bag or a piece of fleece over promising blooms and remove it once the shower passes — water sitting in the petals marks them and can rot the centre. In a heatwave, a little shade netting over the best plants keeps petals from scorching.

Cut at Peak Freshness

Timing your cut is everything. Dahlias are at their most turgid in the early morning, so aim to cut before nine o'clock, or go out again in the cool of the evening.

• Take a bucket of cool water to the plot with you, and sharp, clean secateurs.
• Cut on a slant, leaving a stem long enough for the vase — usually 30 to 45cm.
• Plunge the stem straight into the water. Never let air travel up the hollow stem.
• Strip the lower leaves that would sit below the waterline, as they sour the water quickly.
• Condition the blooms in a cool, dark shed or garage for twelve to twenty-four hours at around 10–15°C. Avoid a domestic fridge, which is often too cold for dahlias and can blacken the petals.

Don't cut too far ahead. A bloom cut three or four days before the show will be past its best on the bench. Overnight conditioning is ideal.

Clean and Groom Before Staging

Presentation is where careful growers quietly gain ground. Earwigs love dahlias and will happily sit deep in the flower head, so tap each stem gently over a bucket and shake them out before you travel.

Use a soft artist's brush or a barely damp cotton bud to lift specks of grit, stray pollen and insect damage from the petals. Work from the centre outwards, supporting the bloom with your other hand. Don't wash the whole head — water leaves marks and encourages botrytis. Snip out any bruised or torn ray florets with fine scissors, and handle blooms by the stem only, never by the petals.

Choose for Uniformity and Stage It Well

When you have several candidates, lay them side by side and be ruthless. Select blooms of the same size, the same depth of colour and the same stage of opening — roughly half to three-quarters open. Fully blown flowers flag within hours, while tight buds simply look unfinished. Check the centre of each bloom: a green core or a split centre is a fault judges will spot immediately.

Arrange your stems so the heads sit at a consistent height and face outwards without crowding. Fill the vase to the required level, remove any foliage below the waterline, and carry everything in a box with crumpled newspaper packed around the stems so nothing shifts in the car. Keep the box out of direct sun and arrive in good time to stage calmly.

Once on the bench, a final few minutes with a damp brush and a careful tweak of a petal is all that is needed. Then step back, let the blooms do the talking, and enjoy the rest of the show — you have earned it.