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Problems we can all come up against.

Byline: By Peter Surridge

When a gardener acquires a greenhouse, new cultural opportunities open up.

The first two activities will probably be growing tomatoes and over-wintering tender plants, though even these apparently basic procedures are not always straightforward, as these queries from readers this summer indicate.

Q Last year I took cuttings from my bedding geraniums (pelargoniums) in August and over-wintered them in my new greenhouse. I allowed the cut edges to heal then potted them up in very sandy compost, keeping moisture to a minimum. However, there was grey mould on some of the stems where I've cut them back. If it happens again this year, I would like to know how to treat grey mould. I don't want to use a chemical spray.

A August is the right time but it is better to pot pelargonium cuttings fresh rather than risk allowing disease to enter through the new cut. Cool, humid conditions encourage the fungal disease grey mould, so ventilate your greenhouse regularly or grow the cuttings on a windowsill indoors, in an unheated, north or west-facing room. Try using gritty, rather than sandy, compost, and ensure it is sterile by buying fresh compost if necessary. Sterilise your knife and pots, too, before taking cuttings. Once grey mould has infected a plant, it cannot be eradicated.

Q This year I planted tomatoes in the greenhouse border. I put manure on first then mixed compost out of growing-bags with the soil. The plants grew to over 2m (6ft 6in) before I nipped them out. There have been plenty of flowers on each truss, but they keep dropping and only a few tomatoes have formed. What is going wrong?

A This problem, called blossom drop, is caused by a failure in pollination. It can arise if your greenhouse is too hot or cold, or the atmosphere too dry or humid. The optimum temperature is 20C (68F) and ideal humidity is 70pc. On hot, dry days, the humidity can be increased by watering the borders, paths and plants thoroughly around midday. Pollination can be assisted by tapping the flowers gently.

Other questions this summer covered concern about the ultimate size of a magnolia tree, curiosity over the many terms for categories of flower and shrub and a fruit tree problem.

Q Could you give me more information on a shrub I was given as an anniversary present. The information on the label says "Magnolia Susan ( a slow growing Japanese shrub, winter buds grey-hairy producing beautiful white flowers stained rose purple." Can you tell me any more about it, especially its eventual height and spread, so I can decide where to plant it, giving it sufficient growing space?

A Magnolia Susan is a very beautiful form ( one of the Kosar hybrids between two Magnolia stellata varieties, `Nigra' and `Rosea'. It remains compact for many years and flowers in late spring. In ideal conditions it could eventually reach 2.4m (8ft) in height and somewhat less in spread.

Q Can you please advise me what the following mean: herbaceous plant, biennial, half-hardy annual, hardy annual, alpine and hardy deciduous shrub?

Herbaceous plants die down in autumn, produce new shoots and flowers next year, such as lupins; biennials are sown one year, flower the next, then die, like forget-me-nots; alpine is a term given to many kinds of small plant, some of them originally from alpine regions, that are suitable for rock gardens; a hardy deciduous shrub can withstand cold weather but loses its leaves each autumn; half-hardy annuals are flowers, normally sown with heat or under glass in early spring, then planted out as summer approaches; hardy annuals, also flowers, can be sown direct into the ground, generally around April. All annuals grow, flower and die the same year.

Q I think I have serious trouble with my Victoria plum tree. The tips of the branches are dying and the leaves are turning brown and dropping off, although the tree is loaded with fruit. It seems that only one side is affected. Can you offer any help please?

A Some of the symptoms you describe could indicate bacterial canker, a serious fungal disease for which there is no effective treatment and to which the variety Victoria is susceptible. Cankers are first evident in autumn or winter with depressions in the bark, sometimes on only one side of a branch, bearing sticky gum, often amber in colour. In spring the leaves show dark brown circular spots which drop out, leaving `shot-holes.'

Q Our garage is overrun with ivy. I have removed all I can. Can you tell me what chemical I can use to kill the ivy.

A You should not need a chemical to kill the ivy. Find the points at which the stems emerge from the ground and cut through them.
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Copyright 2004 Gale, Cengage Learning. All rights reserved.

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Publication:The Journal (Newcastle, England)
Date:Aug 7, 2004
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