We are delighted to welcome Pippa Greenwood to our Blog and to start things off we have a small Q&A session. Please feel free to pose your own questions at the bottom of this list. We'll get our panel of experts to help answer them.

Pests & Diseases


Q: I have noticed a brown, powdery substance on the under surface of the leaves. It is on my plums and something rather similar on my roses. Is this rust? A: Yes indeed! Rusts, of all the diseases, are probably those which thrive and spread particularly well when the air is moist. At this time of year they often become a real problem. I have also rust on the foliage of garlic this year. You should ensure that you collect up and compost, bin or burn all the infected leaves on a regular basis. This will help to decrease the likelihood of them spreading and over-wintering successfully. Generally rust on a plant such as plum or willow is unlikely to have any significant effect on the tree’s vigour in the long term. And so on these plants, I would be less inclined to worry. However, on things like roses, they can have quite a weakening effect after a while. So I would suggest you may like to consider spraying the plants, as well as carrying out routine clean ups. I rely on purely cultural techniques. Such as keeping the rose well pruned, avoiding wetting the foliage and prompt clearing up if rust appears Q: My peach has peach leaf curl disease, can it be saved? A: Definitely ! First you should pick off the infected swollen and reddish purple leaves which develop on peaches, nectarines and edible and ornamental almonds. These are caused by the peach leaf curl fungus (Taphrina deformans) and removing them promptly reduces the risk of the problem spreading. If you then feed it it helps the plant perk up. It should then be able to produce a second flush of clean, new foliage. You may need to spray it with a copper based fungicide. Once the plant is clean again, try covering it with an open-sided clear polythene shelter between leaf fall and spring to reduce the risk of spores landing.

Apple Canker

Q: My apple is showing signs of slight dieback. I have also noticed similar problems on the mountain ash or rowan tree. The dieback seems to be associated with roughened patches on the bark. Is there anything I can do? A: This sounds like apple canker. This is a fungal problem which is quite common and which you may also find on pear trees. The cankers that form start to ring the infected stems or branches. As a result, growth becomes poor and spindly. If the canker rings the branch entirely then everything beyond that point will die back. You should take action promptly because this fungus is likely to spread fairly effectively. I suggest that you prune out all the infected limbs. Take the branches back to perfectly healthy growth and to a suitable outward facing spur or bud. If the canker is present on the main stem or trunk of the tree, then obviously you cannot cut this out. In this case, I would suggest that you take a really sharp knife and attempt to scoop out the entire cankered area. Once more cutting back to really clean and healthy looking wood.


Q: How can I go about controlling slugs and vine weevils without using chemicals? A: Both these pests do have some natural predators in the garden. These include ground beetles, so you should do everything you can to encourage these. In addition, I suggest you attempt to use some of the biological controls. There is a nematode-based control which is suitable for use against slugs and another, quite different nematode. You can use this to control vine weevil grubs. Sadly these are not available in garden centres. This is because, as they are living organisms, they would not survive life in a garden centre for long. But you can buy them from mail order suppliers and these should be delivered promptly, ready for you to use. In both cases they result in the pest being poisoned without posing any threat to other creatures. There are several different suppliers of biological controls.


Q: The garden that I have recently taken on seems to have more nettles in it than anything else. What can I do? A: If you are happy to use chemicals, I suggest that you choose one based on glyphosate. These chemicals are translocated. This means they will be carried down from the foliage into the entire root system. You should find that with one application now and then perhaps another one early next year, you can clear the ground completely. If you don’t want to use chemicals then I suggest you cut back as much of the foliage as you can manually and then cover the soil with cardboard and grass clippings. This will prevent light from getting through to the plants and smother them, so gradually weakening them. You should find that this will help to kill off the majority of the weed growth. However, you may still need to dig out some by hand. Do be wary because both nettles and docks have extremely pernicious underground parts. This means that even a small section left in the soil has the ability to root and form a new plant. Whatever you do, do not compost the underground parts of either of these weeds.

Around the Garden

Q: How can I control the algae which is spoiling my patio area? A: Algae usually builds up because the surface is moist for prolonged periods. So the first thing you should do is to try and find out why this is happening. Certainly check nearby guttering and drainpipes to ensure that there is nothing leaking onto your patio. In addition if the area is quite heavily shaded or gets a lot of run off when it rains from nearby trees, then this too could be involved. There are lots of proprietary patio cleaners on the market which you can use. Do check that the one you choose is safe for use in the vicinity of plants. If you do not want to use any chemicals as such, then quite often, provided you can sort out the source of the excess moisture, you will find that scrubbing the surface of the paving with a stiff brush or yard broom may be sufficient to dislodge the algae. Some people also treat the area with small quantities of salt and find that this works well, although again you must take caution if there are plants nearby. Q: Help! My pond is now bright green and packed full of what my neighbour says is blanket weed, is there anything I can do? A: If your pond has become green and full of a tangled mass of strands of that common problem blanket weed it will not only look awful but may also entangle fish or wildlife as they swim. I find the best method of control is to regularly use a rake or a stick to remove the blanket weed, pulling it out of the pond and composting it or binning it if you do not have a compost bin.Make sure you leave the mass of weed on the side of the pond, and trailing in to it slightly for a few days before composting so that pond life can escape back to the pond!

Plant Selection

Q: Can you suggest a few shrubs that would be looking good in my garden in early September? A: There are lots of things which should be particularly attractive, including potentillas, Perovskia, Indigofera, hypericums, hydrangeas, fuchsias, Hibiscus syriacus, Buddleja davidii, Caryopteris, Ceratostigma, vincas, hebes and Abelia grandiflora. In fact, if you pay a visit to your local garden centre at this time of year, you can be sure that many of the shrubs which are looking particularly good at that time of year, will be prominently displayed, so you have got the pick of the bunch and of course you have also chosen a perfect time for planting. Q: This year I grew some bedding plants from seed, they germinated OK, but many were massively tall, any clues? A: As bedding plants grow it is essential to pinch out the growing tips on the shoots. Doing this helps to encourage plenty of side shoots to develop so creating good bushy, compact plants. This is easily done using your forefinger and thumb. Q: I planted some shrubs and a few trees in my new garden in early spring. I am now scared they won’t thrive, please can you help? A: Trees and shrubs which were planted earlier this year will need extra care and attention right now. Their roots will not have grown out into the soil to any great extent and because the weather is a lot warmer and drier they could easily suffer from drought. Give regular drenchings of water applied in early evening for best effect. Once the soil is thoroughly wetted, if you have not already done so, apply a 5-7.5cm (2-3in) deep mulch over the entire root area and this will help to preserve water. Pippa Greenwood can be heard regularly on BBC Radio 4s Gardeners Question Time where she uses her expertise to advise gardeners on all things horticulture. Pippa Greenwood 1 Pippa Greenwood 2 Pippa Greenwood 3 Pippa Greenwood

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