Clean up the rhododendrons, de-stress tomatoes and cut back seeding columbines: Nigel Colborn’s essential jobs for your garden this week

  •  pruning peony tree – Rhododendrons will soon be over and may benefit from light pruning
  • If tomatoes overheat or become drought-stressed, the fruit can develop physiological disorders
  • Hard areas develop on the uppermost sides of the fruit, then refuse to ripen

DE-STRESS TOMATOES

As we approach 2016’s longest day, on Monday, greenhouse temperatures can rise to dangerous levels – 40c or more. Even with all vents open, nonshaded structures can become solar ovens.

If tomatoes overheat or become drought-stressed, the fruit can develop physiological disorders such as greenback.

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If tomatoes overheat or become drought-stressed, the fruit can develop physiological disorders such as greenback

Hard areas develop on the uppermost sides of the fruit and then refuse to ripen, often staying green and fibrous. Prevent this by arranging shading on your greenhouse.

Use shade netting or paint the glass with a material such as Coolglass. Water tomato plants frequently, never letting them dry out too much.

Try to keep the greenhouse humid by damping down. And don’t forget to leave vents and doors open

CUT BACK SEEDING COLUMBINES

Columbines and other early perennials have run to seed. If you allow these to shed naturally, seedlings will sprout in their thousands. Thus, a cherished plant becomes a weed problem.

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Columbines and other early perennials have run to seed. If you allow these to shed naturally, seedlings will sprout in their thousands. Thus, a cherished plant becomes a weed problem

To control self-seeding, cut spent stems back to ground level before the seed capsules ripen. Early perennials will benefit from this and produce larger, more prolific flowers next spring.

If you want to allow controlled, natural seeding, then leave a few capsules on each plant – but remove most as described.

Do this only with plants whose flowers are well-coloured or elegantly shaped. You can collect the ripe seed later, or allow remaining pods to self-seed.

READER’S QUESTION

Is it true that there’s a butterfly which predates geraniums? If so, how do I identify it and what damage can it do? Mrs I. Royston, address supplied.

Perfectly true. The Geranium Bronze Cacyreus marshalli is a South African butterfly species probably introduced along with imported plants. It was first recorded in Sussex in the Nineties and is spreading.

The adult is a small butterfly – wingspan up to 25mm – related to our native Common Blue. Its wings are dark brown above, with thin, white margins.

Their undersides have brown, grey and cream markings. The tiny caterpillars feed on pelargoniums, eating their way down the insides of the flower stalks, causing damage when large numbers are present.

For this species, there are no specific insecticides, but it’s wise to pick off and destroy damaged flowers and stems.

PLANT OF THE WEEK: PELARGONIUM CALIENTE FIRE

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Most so-called ‘red’ geraniums have a hint of orange in their scarlet blooms. But I’ve stumbled on one with truly deep red flowers

Most so-called ‘red’ geraniums have a hint of orange in their scarlet blooms. But I’ve stumbled on one with truly deep red flowers.

Pelargonium Caliente Fire has both ivy-leaved and zonal varieties in its bloodlines. The blooms are a unique, sultry, glowing red.

Flowering is constant, and the single petals fall easily, making the plants virtually self-cleaning – even after wet weather. That semi-procumbent habit makes it perfect not just for large containers, but also for use in bedding schemes or even dotted about a border.

It would make a pretty house plant, too.

SPECIAL OFFER: HALF-PRICE AZALEA

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Dwarf evergreen Japanese azaleas are a compact plant perfect for borders or growing in pots on the patio

Dwarf evergreen Japanese azaleas are a compact plant perfect for borders or growing in pots on the patio. 

They flower in April and May, and will reach a height of 60-90cm. Grow them in containers if you have limey soil. Pot-grown plants supplied. 

Categories: care of tree peonies, azalea fertilizer tips, pruning azaleas and rhododendrons, pianese flower delivery