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Two lawn invaders and a leylandii hedge dilemma, by garden expert Helen Yemm

The perfect lawn takes a lot of work
The perfect lawn takes a lot of work Credit: gapphotos.com

Every week, Telegraph gardening expert Helen Yemm gives tips and advice on all your gardening problems whether at home or on the allotment. If you have a question, see below for how to contact her.

An invasion of mind-your-own-business

I was recently sent a squashy little package by Diana Ashcroft, clearly at her wits’ end. It contained a nasty little weed with tiny leaves, Helxine soleirolii, more commonly known as mind-your-own-business or baby’s tears, that is invading all parts of her garden. It appears for sale frequently in florist’s shops, sold as a bit of interior potted flimflam with no hint of a warning that it should never be allowed outdoors, where it becomes a tough, rapidly-spreading invader, seemingly dispatched by frosts, only to reappear when everything warms up. So what can Diana do to get rid of it or try to get the upper hand?

Physical removal of patches in lawns has to be meticulous, followed by soil replacement, reseeding and constant hawk-eyed monitoring. Elsewhere, in beds and borders where appropriate, it can be starved of light under a deep mulch, which will kill it. In cracks between paving, I have heard that determined work with a hand-held steamer works.

Glyphosate weed killers (that will also kill any other greenery) do work well, but need a second application when scraps reappear. Meanwhile, you will be faced with otherwise “barren” patches in the garden.

I suspect Diana is going to have to live with this one, unless she is prepared to keep an armoury of products constantly to hand.

Is it worth reducing our leylandii hedge?

Would a 2.1m tall by 1.8m wide leylandii boundary hedge survive if we cut all the branches on our side back to the trunks, just leaving the branches on the neighbours’ side– thus giving us an extra 1m of border while maintaining our privacy?

John Elliott – via email

Trimming a leylandii hedge Credit: Christopher Jones for the Telegraph

From your email it is clear that you know that leylandii hedges do not sprout out from brown wood, so you presumably realise what ugliness would result if you cut your hedge back beyond the “green”.

The soil in that “extra 1m” would, furthermore, be very dry and inhospitable – and absolutely full of conifer roots. Even if you chopped at these and added enough organic matter to the soil to enable you to grow plants to hide the unsightliness, the remaining green parts of the hedge (including a ragged top) 
would also grow faster.

I would think very carefully about this and try to find a way of living with this hedge without butchering it. Can you perhaps trim it harder and more regularly while avoiding going into old wood (which will mean keeping a narrow service path at the back of your border) and perhaps bring the border forward a little by adjusting the line of the lawn?

The other option: start again with a more garden/neighbour-friendly evergreen.