e-mail Jane Owen with your gardening questions: jane.owen1@timesonline.co.uk

I recently purchased part of a neighbouring garden in order to enlarge ours. I have now made the discovery that the new land contains Japanese knotweed. How do I get rid of it please? Yolanda Jones, Herefordshire

As you probably know this is a serious weed in terms of its invasiveness and destructive powers: in some areas of the south west it is undermining motorways. Therefore it is important to get rid of the stuff completely. It is best to follow the advice from the Royal Horticultural Society which you will find on this link www.rhs.org.uk . Please take note of the fact that its remains cannot be put in household waste.

I recently planted a garden-centre bought courgette plant in my new vegetable bed. 12 hours later most of the leaves had been eaten, with only the skeletal structure remaining! The same happened to my radish plants. I can't see any greenfly, caterpillars or slugs, but the bed does rest against a portion of old red brick wall. Would ants eat plants like this, and what can I do about it without digging up all my plants? Catherine Watson, Swindon

Ants are not the culprits and it may be that some of the damage is by snails which love hiding in old brick walls, as I know to my cost. However, I bet that the main damage is caused by pigeons and, before you say that you can’t see beak marks, pigeons are as untidy when they come to eating as they are when they are crashing about in trees. Bird scarers, from cats to scarecrows, are the answer.

I am devastated, there is something wrong with my beautiful wisteria - last year it was a mass of flowers and leaves and this year there are a few mature blooms and the rest haven't developed at all. what do I do? Do I cut the plant, or do I leave it until next year and see what happens? C Adams, Bucks

These gorgeous plants give such delight when they’re growing well and such distress when they aren’t. I think drought may be the problem – and the damage may have occurred last year. So, what’s the next step? The problem about cutting it off at the point where the good growth begins is that this good growth may be coming from the rootstock which will provide only sparse flowers. Before cutting have a look to see if can see the union, or joint, which will tell you whether the growth is from rootstock (below the union) or the cultivar. If the former you may as well dig out the plant. If the latter it’s probably worth cutting the plant back, keeping it well watered and giving it a feed of superphosphate and sulphate of potash. Also, make sure the area hasn’t become shaded and, if it has, cut back whatever’s doing the shading.

I have some delphiniums which were just about to flower against a warm, westerly wall but they have just been snapped by the wind. Is it worth staking them at this stage? Simeon Lloyd, London

If the stems really are snapped and held on only by a few strands of stalk you should cut them off for a cut-flower arrangement. The cut stems will make multiple small flower heads later in the year. On the other hand if the stems are simply bent you can probably stake them to make a good display in the garden – and then cut them down as soon as they start to go over in order to get a second flush, as above.

For the second year running my rocket crop has lots of holes as if its been shot by a shot gun. L.Hawes, Staffs

This is not a shot gun attack, you will be relieved to hear, but attack by flea beetles which are small and jump in rather the same way as fleas. Derris dust will sort them out – and regular watering in dry spells will help keep infection at bay.

Is there such a thing as a continuous flow, fine-tuned applicator for weedkiller? I am having to paint weedkiller onto bindweed throughout a 2m by 1m bed which is packed with precious perennials. Daphne Streatly, Worcester

The sad thing is that, in the old days before the advent of the EU, I would have been able to suggest de-canting the herbicide into an old roll-on deodorant bottle. This makes application simple, accurate and safe so long as you wear rubber gloves and thoroughly wash the container afterwards. Given that I am no longer able to make such a suggestion without incurring the wrath of the EU police I am at a loss as to how you can solve your problem.

I’d like to give a tree and a rose for my parents’ silver wedding. The tree should not be too large. Their soil is slightly acid. Name and address withheld

It would be tempting to suggest the Wedding Cake Tree which is a favourite of mine with creamy-white and green leaves but I think its close relation, Cornus alternifolia ‘Argentea’, is even more attractive. Numerous magnolias would fit the bill by having creamy white flowers. So would a close cousin of the magnolia, Michelia doltsopa, which has large white scented flowers in winter. White Flowering cherries – like the scented Prunus ‘Shirotae’ are another good bet. Roses come in so many shades of white you are spoiled for choice. The rambler, Wedding Day is one thought or Silver Wedding from Peter Beales www.classicroses.co.uk

I went to your lecture a couple of weeks ago (which I enjoyed a lot by the way) and would like to know more about some of the plant hunters you mention. Marianne Davies, London

Robert Fortune and several others wrote books about their adventures and all can be found at the Royal Horticultural Society's wonderful library www.rhs.org.uk/learning/libraries in Vincent Square (which is FREE and open to anyone). ‘The Plant Hunters’ by Toby Musgrave, Chris Gardner and Will Musgrave gives a great overview of the subject and Maggie Campbell-Culver’s ‘The Origin of Plants’ does so in even more depth. Finally, and just out and so I have not yet read it: ‘Gifts from the Gardens of China’ by Jane Kilpatrick (Frances Lincoln) which traces the rich history of British plant hunting in China.

e-mail Jane Owen with your gardening questions: jane.owen1@timesonline.co.uk

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