– The red and yellow foliage of rust-infected mahonias might be the most dramatic and intentional of variegations, did it not weaken the plant to death. If yours has it bad, spray it to save the new foliage, or think about getting rid of it.

– Go over colonies of that stalwart of dry shade, Euphorbia robbiae, cutting out the shabby flowered stems right at the base – next year’s display will look 100 per cent better for it. Wear gloves to protect against the sap.

– Phlox are thirsty beasts, but so invaluable in high summer. Peppery perfume, too. If they wilt, the flowers don’t last half as long. Make sure they never lack for water, especially in hot, windy weather – the test of all thirsty plants.

– Time to go over roses that have completed their flowering, taking off dead heads and shortening flowered shoots to a healthy bud.

– As long as the soil is moist, you can use a selective weedkiller on lawns sown this spring, to prevent broad-leaved weeds smothering seedling grasses.

Readers’ queries

I have two 4ft Japanese maples that are fighting for space. How and when should I prune them to maintain their mound shape? Mrs G. Fegan, Oldham

Everyone loves Japanese maples for their delicate leaves, poise and graceful mounding habit. And everyone forgets that, after two or three decades, they look like VW Beetles, even if the naked branch structure is elegant.

To keep that elegance, they need room to develop unrestricted and unpruned. The older they become, the slower they grow, which is helpful; you might just thin out an old one, perhaps, open up its branch structure a little in winter with secateurs, to stop it seeming so solid in summer. But if the problem is the sheer area covered, then either the design must change to accommodate the tree, or it has to go.

Maybe you should lose one of your maples; the other will cover its gap soon enough. Or just let them rub along together, self-limiting by root competition, overlapping hip to hip, like old folks on a bench sharing their sandwiches.

We’ve inherited a 30ft pear tree that is swathed in flourishing ivy up to about 20ft. The top of the tree appears to be fine and there is the odd healthy branch poking out below. What is the best way of preventing the ivy from killing the tree? Mr J. Howell, Sussex

Ivy kills trees not by strangling, but by its sheer weight, especially under rain, snow or wind. Left unchecked it can also shade out enough of a tree’s foliage that it dies. So, either saw through the ivy at the base or get up there and chop out all the bulk and freestanding growth.

Wild pears tend to be big, and their corrugated, twisting bark is one of the most attractive to be seen on a flowering tree. Their golden fruits are good, too. But, be warned: the wild pear is not a cuddly customer – it bears long, vicious spines as nasty as that produced by any robinia or thorn. In fact, perhaps spine is the wrong word, for the ends of the stubby little spur growths along the branches are more like skewers. On dead wood, they will be like iron.

stephen.anderton@thetimes.co.uk

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