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Gardeners' Question Time - Crickhowell

Eric Robson takes the Gardeners' Question Time team to Crickhowell in South Wales, with Bob Flowerdew, Matthew Biggs and Christine Walkden taking questions from the audience.

This week Eric Robson takes the Gardeners' Question Time team to Crickhowell in South Wales, with Bob Flowerdew, Matthew Biggs and Christine Walkden taking questions from the audience.

Produced by Howard Shannon. A Somethin' Else production for BBC Radio 4.

Q: I have some Photinia Red Robin plants that are losing their leaves and are covered in black spots. What is this and what can I do about it? A: This sounds like Photinia leaf spot, which is an extremely common fungal disease. You could try to use a general fungicide to clear it up, but the plant probably has a better chance of survival if you just concentrate on its general health, making sure it's well fed and vigorously growing.

Q: I use molehills as compost but a friend recently warned me that they are rotten with weed seeds, is this true? A: The soil brought up by molehills tends to be from lower down in the ground, so actually there might be fewer seeds in it than usual topsoil. It's already well worked and it may also contain some manure content, so there's no reason why you shouldn't be using it.

Q: Can you advise me how to grow lavender successfully from seeds or cuttings? A: English Lavender is probably the best variety to go for as it's the most likely to withstand the weather. Take semi-ripe cuttings from young growth from the end of July through to the start of September planting them in gritty compost at the base of a sunny wall, which will give them good protection from the rain. The more cuttings you take the better chances you have.

Q: I'm looking for some high-impact climbers to grow up a 10m tall north-facing fence. What would you recommend? A: Try Schizophragma integrifolia which has beautiful dark green foliage and white 'pocket handkerchief' flower heads that resemble Hydrangeas. Akebia quinata is also stunning with lovely purple flowers and produces a wonderful chocolately scent from early in the year. A new variety from Taiwan called Akebia longeracemosa is also very nice and has impressive clusters of flowers. Don't overlook more commonplace plants such as the Golden Hop and Honeysuckles such as late Dutch reds, ordinary English, and the Etruscan Honeysuckle which has beautiful golden yellow flowers.

Q: I have an allotment which I try to keep free of chemicals. With this in mind what flowers would you suggest I grow can that be used for both companion planting and cutting? A: Marigolds work well - the African variety is bigger and make good cut flowers whereas the French variety is a strong companion. They also give off substances that help get rid of nematodes in the soil. Cornflowers, Corn Cockles, Phacelias and Nigellas all have lovely flowers which are good for cutting and also attract lacewings and insects which will eat nasty greenfly. Herbs with flat flowering heads such as Dill, Sage and Fennel would also be nice.

Q: I've had an allotment for about four years and would like to know if I should start manipulating the pH of the soil? A: You can buy a cheap pH tester from the garden centre to check the soil and you should be aiming for it to be around pH 6 1/2 to 7 1/2. If it's slightly acidic it can easily be fixed by using garden lime, spreading a thin layer across the ground everywhere except your potato patch (as it will make potatoes look 'scabby'). When handling lime make sure to use gloves, and avoid using it at the same time as manure.

Q: We have an old bicycle that we'd like to put to use in the garden as a planting feature. Any ideas? A: Try sticking a wheel on a pole and running wires back down to the ground from the spokes - it would make a great teepee to train climbing plants up. You could always use the saddle as a garden stool too.

Q: My brother and sister-in-law brought me a small container of elephant dung back from a trip to South Africa. How can I use it productively in the garden? A: If it has come from Africa rather than a zoo over here- we'd suggest against releasing it in your garden incase it contains any foreign diseases which could be harmful. It should probably just be disposed of hygienically.

Q: I wish my lawn needed mowing less often - can you suggest ways to slow it up? A: If you want to turn it into a wildflower lawn, then you couldsow Yellow Rattle which is partially parasitic on grass and feeds from the roots which will certainly slow it down. Another simpler suggestion would be to treat yourself to a larger lawn mower, which will make it quicker to cut!

Q: Why can't I grow parsnips very well? A: Terry Walton's trick for the perfect parsnip is to sow the seeds on damp kitchen towel and place them in an airing cupboard. Once the seeds have germinated, carefully plant a couple in a fibre pot with the base chopped off and leave them in the greenhouse until they're looking bigger (a sand/compost mix is best). Then take the whole pot and plant it in the ground, sit back and await the results.

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