Monthly Masterclass: July

Do it: trim box hedging

Cutting box hedging in the Walled Garden

Step 1

Box plants (Buxus sempervirens) can help create formal structure in the garden. Their neat evergreen leaves and naturally dense habit mean they are perfect for clipping into a low hedge or topiarised shape. Not only this, but they also grow happily in awkward dry and shady spots. Box plants can be cut at anytime during the growing season but are best trimmed from mid-summer onwards when the foliage has begun to harden. Cutting too early will leave soft new growth vulnerable to late frosts and sun scorch. Box plants cut in July and August will likely need trimming again before autumn to tidy up the re-growth which follows.

Mark a cane at the height you wish to cut your hedge

Step 2

Cutting box hedging can be a nerve-racking task. Use these tips to help you get it right. For larger hedges a string line can be erected across the face, held between two bamboo canes. For smaller hedges, simply marking the desired height on a stick or cane with a pen is sufficient. This can then be held against the hedge at various points for comparison. Powered hedge cutters are great for getting through long hedges that take lots of time but handheld shears are better for the nervous gardener. Using non-powered tools forces you to slow down and pay closer attention to the task at hand.

Clean with garden disinfectant followed by oil

Step 3

And if straight lines aren’t enough to contend with – there’s also the threat of box blight to consider! Box blight can quickly decimate whole hedges causing unsightly bare patches to form where foliage blackens and dies. Box blight is a fungal disease. The spores travel in moist conditions; particularly wind-blown rain. Choose a dry afternoon to cut your hedge when morning dew has disappeared and there is little chance of rain. The early stages of box blight are difficult to detect so even if your plants look healthy, clippings should be cleared from the top and base of the hedge and kept away from the compost. Hedge cutters, shears and secateurs should then be cleaned with a garden disinfectant followed by oil for lubrication.

Grow it: Californian tree poppy

What: Californian tree poppies, or Romneya coulteri, are large sub-shrubs growing to about 2 metres tall with silvery-green foliage and white poppy-like flowers in summer.

Where: Grow in hot and dry borders with plenty of shelter from wind. A south or west facing wall, giving some protection and plenty of sun, is ideal.

How: Californian tree poppies require very little maintenance. Dead foliage should be pruned to ground level at the end of the season. Plants may be vulnerable to powdery mildew and verticillium wilt. They should be well watered and fed in response to both.

Californian tree poppy in the Top Border

When: Plant in spring and leave well alone; Californian tree poppies hate being disturbed once established. A protective mulch of organic matter can be applied before frosts arrive and root cuttings can also be taken in early-winter as insurance against losses.

The Gardener’s Verdict:

“Californian tree poppies are a true luxury plant. They need a little bit of special attention in the first instance and plenty of warm, still air, but once they are happy they become truly spectacular additions to the garden  – even a bit of a thug!

A better common name is the fried egg plant. The flowers have tissue-paper white petals surrounded by a mass of bright yellow stamens in the centre and look to all the world like a cracked egg, floating atop long narrow stems, sunny side up.

Once established the Californian tree poppy will spread underground by runners and sometimes multiply vigorously. A large border planted with plenty of other robust perennials and shrubs will help to keep it in check.

We grow ours in the Top Border where it is sheltered beneath a south-facing wall and terrace above. Here, with added warmth, some foliage even survives the winter where usually it would die and get cut back to the ground.

Other sun-loving plants with thick and succulent leaves make perfect partners. Sedum ‘Herbstfreude’ has fleshy, glaucous leaves, and pink flowers which remain dried throughout the winter.

Those grown in front of a wall for protection can also be paired with a suitable climber. Purple-leaved plants, such as Vitis vinifera ‘Purpurea’, will add to the luxuriant effect, combining well with the silver leaves of its companion.”

Daniel Cartwright, Horticultural Supervisor, Winterbourne House and Garden

The dreaded Himalayan balsam

Read it: Monthly Masterclass: June

Losing the war against weeds? Our gardeners get to grips with some of the worst in last month’s Monthly Masterclass: June. Find out how to tell your annuals and perennials apart and how to stop them coming back for good!

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