Garden advice: Thorny problems

Garden tips and advice from our resident expert Helen Yemm. This week: tidying up clematis, moth orchids and tarragon trials

Tidying-up clematis

This week's Big Query comes from our Gardeners' Forum. Roosje (no surname) has a Clematis 'Mrs Cholmondeley' that flowers prolifically each year. Aware that this belongs to the early flowering Clematis Group 2 (sometimes called Group B), Roosje knows that, according to accepted wisdom, it should be sparingly pruned with a minimal tidy-up in February.

	Free spirits: Orchids cope well with neglect

But, although it flowers well, her plant consists of a single stem from the ground, with few signs of life visible in its first 1.5m (5ft). Roosje wonders what will happen if she cuts the plant right down. Can she assume that it will make new shoots from the base and fill out?

Hidden in that innocent phrase "tidy-up in February" lurks a garden minefield: for the over-zealous, any brown-looking stems are fair game at this time of year.

Give them a pair of secateurs or some well-oiled loppers and the whole garden may end up looking as if it has been grazed by a herd of hungry rhino. Oh yes, February can be a difficult month for itchy-fingered action men and women.

"Tidying up" Group 2 clematis at this time of year is an extremely delicate operation, to be tackled only by those with a delicate touch and a lot of patience.

The best new shoots on the tangled, twiggy growth made the previous year will carry this year's flowers. You need only to snip away the most wayward extensions and hard-to-identify shoots that are damaged or dead, leaving intact as many of the new, fat green buds as possible.

But it is difficult to see what is what and cut important stems by mistake. Thus, too little is generally tidied. Or, worse, the plants are left alone to get even more tangled and messy. After a few years, the whole mass hangs tipsily off its original supports, making the pruning and general care of any plants over which it is clambering almost impossible.

Once things get to this stage - or if the flowering growth is all coming from a single, vulnerable lower shoot - complete renovation might be needed. The plant will not die if cut severely now - even to within a few inches of the ground.

Given a hefty mulch of something rich, the plant should produce masses of new growth from ground level. However, there will be absolutely no flowers on this new growth in May and June - and maybe only an odd smattering of blooms in early autumn.

It is a good idea to take the chance to renew old wires and supports and prune and tie up neighbouring plants. This is not the sort of operation that should need doing often, especially if you start being braver with the annual February tidy-up of the clematis thereafter.

Moth orchids

Catharine Bright from St Quentin in France loves her moth orchid (Phalaenopsis) but complains that no newspaper gives advice about getting them to flower every year. Well I do, quite often, but since emailer Liz Ockendon also asks about them, I will do so again.

The moth orchid is, as Sarah Raven pointed out last month, the easiest of all the orchids to grow because, unlike others, it tolerates the dry air of centrally heated houses.

It also seems to thrive on neglect - up to a point. Once plants have finished flowering, you should cut the flower stems down by about a third, to just above one of the small swellings or scars that will eventually turn into a bud. Then a new shoot should appear (if you are lucky, it may even produce two branch-lets).

Over-watering is to be avoided at all costs and the pot should dry out completely between watering and never be allowed to stand in water.

Liquid feed can be given monthly in the summer - or you could use a neat little slow-release Fito drip feeder for orchids (available from garden centres or www.theonlinegardener.com) that you up-end- in the soil.