Topical questions & answers
Green manures and the vegetable garden
Phacelia tanacetifolia in flower
Question ...
I want to use green manures on my vegetable plot between crops this season, and then over winter. I have a 3 year crop rotation in my vegetable plot:
- Section 1 - potatoes, carrots and parsnips.
- Section 2 - brassicas.
- Section 3 - beans, lettuces, beetroot, onions, and leeks.
Can I use just one green manure to grow in all the cropping areas, as well as over winter, or do I need to choose two or more types?
Answer ...
It is better to use a range of green manures, as they fit into different plant families. Here are some suggestions.
- Fenugreek - Legume family; frost tender; short to medium term green manure for late spring to late summer use (depending where you are located) Good weed control.
- Phacelia - not related to any vegetable crops. Good for short or medium term use. May survive the winter in warmer areas.
- Tares - Legume; winter hardy. Good for sowing in August/ early Sept to overwinter. Good weed control. Good before brassicas as they provide extra nitrogen in the soil.
- Field beans - Legume; winter hardy. Only worth growing if you want to sow something as late as November.
Our Step-by-Step Guide to Green Manures, which is available from The Organic Gardening Catalogue, will provide you with all the information you need about choosing and growing green manures.
Garden Organic members can view our shorter Get Started guide to Green Manures for more information.
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Top of pageApple & pear scab
Badly damaged apple from
neglected scab infection
Question ...
I have had a great problem with scab this year, on both apple and pear trees. What should I be doing to get this disease under control?
Answer ...
Unfortunately the UK climate is so wet that scab will always be present, and you’ll never really ‘control’ the problem. There are however certain steps to take to reduce the problem.
- Clear all up fallen leaves, and fallen fruits. Spores will linger on infected material, surviving the winter very easily, ready to re-infect the tree in spring. If there are too many leaves to rake up, go over the area with the mower. This will chop up the leaves, and they’ll decompose before next season. Alternatively, water the leaves with nettle tea, or a dilute urine/water mix (1 part urine to 20 parts water) as this will speed up decomposition.
- When choosing trees for your site, make sure they have some resistance. Discovery for example seems to be more tolerant. Ask the nurseryman for advice, and check with the Directory of Apple Cultivars* for details of the trees you are considering.
- Prepare your site really well. Scab thrives in humid wet conditions. A good airflow through the tree is essential. Poor soil conditions will also encourage scab to take hold. The trees must grow well, and without stress. Roots should never sit in waterlogged soil, nor dry out in sandy, hungry soils.
*Directory of Apple Cultivars by Martin Crawford. Pub: Agroforestry Research Trust.
ISBN 1-874275-40-8. Your local library should be able to source a copy for you.
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Wood ash and the organic garden
Question ...
I have a plentiful supply of wood ash that I want to spread on my allotment. How can I do this without it forming a sticky mess or blowing around and getting in my eyes? When would be the best time to do this and which crops would benefit most?
Answer ...
Wood ash is a good source of lime, potassium and trace elements. Ash from a bonfire is best added to the compost heap where the nutrients will bind to organic matter and humus particles in a form that plants will be able to use. Wood ash should never be applied directly to the soil as it is quickly leached out of the soil. Using wood ash from preserved, painted, stained or treated wood is not recommended as there may be toxic elements remaining within the wood ash.
Apple Identification
Question ...
Every year our lovely old apple tree gives us a bumper crop of really tasty apples. We’d love to know what the variety is so we can recommend it to friends and neighbours. Can Garden Organic help?
Answer ...
Apple (and other fruit) identification is a specialist skill and is not a service offered by Garden Organic. Brogdale Horticultural Trust offer this service but there is a charge. For more details see www.brogdale.org/fruit_identification.html. Visitors to Garden Organic Ryton's Apple Day on 5th October can have up to three varieties of apple identified for a donation of £1.
Biological control for vine weevil
Vine weevil larvae
Question ...
A Begonia in my conservatory has been looking very sickly. When I inspected it closely I found very few roots and the compost infested with white ‘C’ shaped grubs. What are these and what can I do about them?
Answer ...
This sounds like vine weevil, a common pest of potted plants, especially indoors. The biological controls for vine weevil, Steinernema kraussei, are very effective against the grubs of this pest but will not damage the adult population. However, grubs are the main problem for potted plants, although the adults may cause some cosmetic damage. The control is best applied outdoors during September, October or November, although it can also be used in March. Indoors they can be used at any time of year. The main criteria is that the soil temperature remain above 5 degrees Centigrade – this should not be a problem in the autumn. Outdoors, you should not be able to find any grubs during the summer months as they reproduce in spring and autumn. The vine weevil biological control is available from The Organic Gardening Catalogue.
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Garden Organic is the working name of the Henry Doubleday Research Association (HDRA).
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