Althorp’s head gardener answers your gardening problems

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Head gardener, at Althorp House, in Northamptonshire, David Williams, takes on the challenge of answering your gardening problems and questions this month...

1: My house is heavily shaded by some veteran oak trees, which have tree preservation orders on them. The result is that the roof of my house becomes heavily encrusted with moss, which periodically I have removed. Is there a treatment that I can use to prevent the moss from growing?”

David: “If the tree has a tree preservation order (TPO) on it that no work can be done to it, you just need the permission of the council to do it.

“Get in touch with the tree office at your local council and explain the situation, that you need to do some thinning to the crown to let more light in.

“They will normally send out all the paperwork you need to fill in and once they have received it, normally they will carry out a site visit, where the tree officer will look at the site and tree. They then have a set amount of time to agree to the work being done or decline the request.

“In the meantime there is a product you can use to kill the moss called Armillatox, which is available from most garden centres. Just follow the manufacturer’s instructions. You may have to brush off the dead moss and reapply a couple of times a year, this is a natural product so should not cause any damage to your roof tiles like some patio cleaners would.”

2. One side of my garden is heavily shaded, do you have any suggestions for plants, especially herbs, that might grow in an area which has very little light. This area is also paved so I would need to be able to grow them in pots.

“The problem with herbs is that they are mainly from the Mediterranean, where they enjoy hours of baking hot sunshine and are not ones to grow in the shade, but there are a few herbs that will tolerate a bit of shade. Parsley, lemon balm, coriander, chives, Angelica, chervil, sweet Cicely, mint and tarragon will all do well in pots with the exception of Angelica as this can grow to 6ft tall.”

3. I grew courgette plants in a vegetable patch two years ago and they produced loads of courgettes until the end of the season when the leaves got a mildew look to them. Since then, in the last two summer, my plants haven’t grown in the same spot at all. Will I never be able to grow courgettes there again?

“Getting mildew on courgettes will not prevent you from growing courgettes again. It’s a fungal disease that is caused by dry growing conditions. This is easily rectified by keeping the soil moist during dry periods and employing a spray with a fungicide, that can be used on the first sign of mildew on the plants. As long as you plant out good vigorous healthy plants in well prepared soil you shouldn’t have any problems.”

DO you have a problem you would like David to try and solve? Please email Nicole Le Marie at or write to her at Northampton Chronicle & Echo, Upper Mounts, Northampton NN1 3HR. *David is better placed to answer your questions if you accompany them with pictures, these must be sent in digital form.