Top tips for fences and hedges - and how to avoid common mistakes in the garden

Plus an expert guide for tackling an acanthus with mildew and restraining a passionflower

Taking control of your garden boundaries is easier than you might think

Many of us have decided that the time is right to tackle our gardens and outdoor spaces but don't know where to start. The solution to creating your own green oasis, however, might be simpler than you think.

Telegraph gardening expert Helen Yemm has given her top tips and advice for tackling your boundaries by using fences and hedges to create the perfect spot.

So, whether at home or on the allotment, take a look below to ensure that you avoid some of the most common mistakes.

Fences

Covering fences has its problems. If you must have climbers:

  • Don’t expect any of them to magically shinny, unaided, up a sheer 1.5m fence just to reach 30cm of trellis attached to the top of it. Slatted fencing, while being admirably windproof, is not very climber-friendly either. Therefore:
  • It pays to pre-install some appropriate support for climbers: a 15cm grid of wire suits most kinds, be they twiners (e.g. jasmine), or graspers (e.g. clematis). Train or spread their low growth sideways rather than just let everything shoot upwards.
  • Summer jasmine and so-called evergreen honeysuckle are particularly difficult, top-heavy plants for clothing fences. Neither flowers well after hard pruning (which they will eventually need). Check my planting suggestions for pergolas, below.
  • Evergreen flowering shrubs, or those with interesting leaves, appropriately pruned and trained, are a lower-maintenance solution than climbers for covering or hiding walls and boundary fences. Threading them through with late-flowering clematis (the “easy” ones that you can prune hard), gives them an extra dimension.
  • A word on pergolas, in similar vein: it would be short-sighted to plant high-maintenance climbers (e.g. rambling roses, wisteria) on pergolas to grow up the side of a building, especially if you are getting on in years, unless you have reliable, knowledgeable help. Instead, choose something slower growing and easier to manage (amenable trachelospermum or a small climbing rose, for example).

Hedges

If you are planning wildlife-friendly hedges, or are lucky enough to have them already:

  • Leave an access path if they back a border, so you can more easily gain access to cut hedges, prune climbers and support/fiddle around with back-row plants.
  • Buy a tripod ladder (with an adjustable front leg) for hedge cutting. Get one a size up from the one you first thought of.
  • Cut hedges every other year to a point lower than the height you like them to be, so that cuts in between times are into soft growth.
  • Don’t forget to also take some lower growth out of hedges, to encourage fresh growth that will help maintain their bulk.
  • Spare a thought for your own and your neighbours’ eardrums and use quiet battery power: I have had a Bosch AHS 52LI trimmer (with a spare battery as a backup), for several years and it is still going strong.

An acanthus with mildew

For two years, since it was planted, my Acanthus mollis has failed to make the kind of statement I expected in my admittedly rather shady garden. How can I persuade it to work?

Rosy Williams – via email

Acanthus mollis growing in shade in Brompton Cemetery Credit: Andrew Crowley

The picture you sent me, taken last summer, showed, as you describe, a complete lack of flowers and some grey and stunted leaves that are clearly suffering from powdery mildew, to which acanthus is particularly prone when grown in dry conditions. I should say here that it is not unusual that your plant has not produced any flowers in its first two years, as this is a perennial that needs to get its feet well down before it does so.

However, you can try to tackle the mildew. Shady gardens are often also, for obvious reasons, quite dry gardens, so mildew can present a problem, and not just for acanthus. This year, before your plant gets going, gently fork a little organic matter into the soil around its roots to enable the soil to retain moisture.

Should the new leaves show signs of mildew again this year, cut them back completely, apply a dilution of a seaweed fertiliser and also then spray the replacement foliage that will rapidly appear with a systemic ­fungicide (Provanto, for example).

Be sure to keep the plant well watered in hot, dry weather. Prevention of mildew is far easier than a cure, so a second spray with fungicide a few weeks after the first may be a sensible idea.

How to keep a passionfruit tidy

Emailer Ken Brown has been carefully training a much-beloved passionflower (the “common orange-fruited, inedible kind,” he says, presumably Passiflora caerulea) on support wires on the south-facing wall of his house for years, trimming back its extremities and wayward bits each spring. It then produces new leaves each spring, as well as masses of flowers all summer. Someone suggested that he should cut it back further each year as it would retrace its steps quickly and would look all the better for it. What do I think, he asks.

There really isn’t a right or wrong about this. While it generally does not die back in winter, a mature passionflower of this kind gradually starts to produce, as it ages, less greenery from its lower half and more from its extremities.

I grew one for a few years in a former garden. Personally, I didn’t like looking at its “in yer face”, scrappy, virtually leafless undercarriage at a time when everything else in a garden was starting to look glamorous, so I became a member of the “cut it back to about a metre from the ground to make it start again” gang. After all, I reasoned, after a few years a passionflower will have developed a mighty root system that will enable it to grow quickly and re-cover its support wires by the end of the year.

It did, although admittedly it flowered and fruited rather later than it would have done if it were treated more cautiously.