WEEDS are springing up in flower beds, but it’s the persistent perennial weeds that cause most problems. While bindweed snakes its way through borders and up hedges, ground elder is emerging from under my neighbour’s fence and couch grass is appearing amid growing perennials and shrubs.

In the past, I’ve taken to zapping these difficult perennial nuisances with systemic weedkiller, which the plant ingests through its leaves and into its root system, killing it gradually over a week or two.

But is there any non-chemical way to be rid of invasive weeds?

“There is no easy solution to perennial weeds, but you can make your life slightly easier by containing the problem,”

says plant ecologist Ken Thompson, senior lecturer at the University of Sheffield and author of The Book Of Weeds.

“Assuming that the bindweed, or whatever, is confined to part of your garden, you should make strenuous efforts to ensure it stays there. Do not inadvertently move it around with other plants, or in soil or compost.

“You can compost roots or rhizomes of perennial weeds safely, but make sure they are dead first. Bake them, drown them in a bucket of water for at least six weeks or beat them to a pulp with a hammer.

“Another priority is speed.

The worst perennial weeds can spread metres in one season, so the time to act is now,” Thompson says.

Persistent weeds require persistent action. It’s no good neglecting perennial weeds for a long time and then going at them like a bull in a china shop.

“Rotavating the whole area generally makes it worse; every bit of root or rhizome will grow into a new plant,”

he warns.

Ground elder will be weakened with persistent hoeing, but that won’t kill it. The rhizomes are shallow, so digging them out is theoretically possible, though it tends to creep among other plants, which makes digging difficult.

It is possible to dig out the rhizomes of couch grass, as they are also shallow, but use a fork, loosening the soil as you go, to pull out long, intact lengths of rhizome.

Perennial nettle rhizomes are shallow and not very brittle, so can be dug out with a fork.

Pearlwort, often mistaken for moss, is almost impossible to hand-pull because bits of stem and root are always left behind. However, as it is so small, it can be controlled through mulching and by filling vacant space with other plants.

Perennial weeds usually pop up among flowers and shrubs, so hoeing is often not possible. If you pull up the weeds, you’ll always leave some shoots behind and even when you dig out as much root as you can, it generally won’t eliminate the problem.

“The only long-term solution is to remove everything – garden plants and weeds – from a bed or border and start again with clean soil,” says Thompson.

It sounds drastic and it is. You can try digging out every piece of weed root and rhizome as soon as you see any growth appearing, or you can cover the soil with a tough layer of old carpet to block out light and prevent weed growth. You’ll need patience, as total eradication is likely to take at least a year.

If you need to remove ornamentals that you want to save, remove all traces of weed root among the roots and temporarily plant them elsewhere. Once the area is weed-free, cover the bed with a permeable, weed-suppressing membrane and replant your saved plants through holes in it.

“Do not be tempted to cut corners by laying the antiweed membrane over an existing perennial weed problem,’ warns Thompson. “The weeds will find a way out through the planting holes and more vigorous weeds will even come through the membrane.”

Alternatively, you could put a thick layer of organic mulch such as compost or bark – at least 10cm (4in) – to prevent weed seedlings appearing.

The Book Of Weeds by Ken Thompson, published by Dorling Kindersley, £12.99.

Best of the bunch – Dicentra spectabilis

OTHERWISE known as Bleeding Heart, this reliable, elegant, clump-forming perennial bears fragile-looking, heart-shaped flowers with rose-pink outer petals and white inner ones, hanging from arching stems, in late spring and early summer.

Its leaves are finely cut and fern-like and it looks good planted with low-growing companions, such as mossy saxifrages, hardy geraniums and hostas, or others providing interest later on in the season. Dicentra spectabilis likes cool, moist and sheltered spots and will grow in partial shade or sun. By keeping the ground moist and sheltering it from the midday sun, the flowers will last longer. The plant grows up to 90cm (3ft) tall and will die down naturally in late summer.

For a smaller, more compact specimen growing 40- 45cm (16-18in) high, go for Snowflakes, which produces clusters of white flowers in late April, or Bacchanal, the darkest red dicentra.

WHAT TO DO THIS WEEK

● Plant summer-flowering bulbs such as acidanthera and tigridia.

● Apply rose fertiliser, gently hoeing it in and around the plants.

● Feed and water newly planted hedges.

● Plant sweet peas once they have been well hardened off.

● Thin hardy annuals sown in March before they become overcrowded.

● For bigger and better blooms in the perennial border, thin down the number of shoots to half a dozen per plant of delphiniums, heleniums, lupins and phlox.

● Continue sowing lettuces, radishes and spring onions for a succession of crops.

● Slip collars around the stems of cabbages, cauliflowers and Brussels sprouts to prevent cabbage root flies from laying their eggs.

● Sow broad beans directly into the ground.

THREE WAYS TO ... Support new climbers

● Tape ivy stems to walls with sticking plasters until they take hold and grow in the direction you want.

● Make a cut in a wirewool scouring pad and use this as a collar around the base of young climbers to keep slugs at bay.

● Fix trellis to battens on the wall. Never attach trellis flush to the wall, as the close quarters provide a disease breeding ground.

GOOD ENOUGH TO EAT... Florence fennel

For a slightly more unusual vegetable to add aniseed flavour to dishes, or simply to serve as an accompaniment, Florence fennel can be sown outdoors in May.

It should be sown in drills 60cm (24in) apart, then seedlings should be thinned to 38cm (15in) when they are large enough to handle.

Fennel is a pretty, decorative plant with feathery foliage, growing to 1.25-2m (4-6ft), but has a reputation for being difficult as it needs a warm summer and well-drained soil to produce the crisp, aniseedflavoured bulbs.

If sowing indoors, harden off seedlings carefully before planting in a greenhouse border or polytunnel in late spring, or outside in a sunny, sheltered spot from midsummer.

Fennel should be watered carefully and not allowed to dry out.

Use a general purpose feed while it is growing and cover outdoor-grown plants with fleece at night if it’s cold, even in summer.

Harvest them when they are the size of a tennis ball and don’t leave it too long or they will bolt.

Pull the whole plant up, cut off the root, lower leaves and top foliage back to a few centimetres above the top of the bulb.