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Common Greenhouse Problems

By: Dr Gareth Evans - Updated: 19 Jul 2017 | comments*Discuss
Over-heating Scorching Ventilation

Although many of the difficulties greenhouse growers encounter depend on the type of plants being cultivated there are some general problems which seem part and parcel of growing under glass. However, fore-warned is fore-armed and with a little care, their worst effects can often be fairly easily avoided.

Seasonal Problems

While the idea of a greenhouse is, of course, to provide plants with a little warmth and shelter, you can have too much of a good thing. Overheating and scorching can cause a surprising amount of damage – especially to young, tender plants – in a relatively short time, so it is well worth taking a few precautions to avoid this problem.

Two things are involved in ensuring your plants’ safety – ventilation and shading. There can never be too many ventilators in a greenhouse, after all, you do not have to open every single one just because they are there, but should the temperature really begin to rise, you can do something about it. Some greenhouse designs can be a little mean in their provision for ventilation – so it is as well to keep this aspect in mind when selecting in the first place.

While some plants – notably begonias, fuchsias and African Violets – are particularly prone to scorching, most plants will need some degree of protection from the direct summer sun. Some form of shading – and there are many types available – applied across the roof and down the side which gets the full afternoon sun will stop your seedlings from being scorched and also help to reduce overheating.


At the other end of the scale, a sudden frost can prove just as damaging and given the vagaries of the British weather, no amount of diligently listening to the weather forecast will entirely guarantee you safe passage on this one. However, a strategically placed fan-heater or similar heater set to “frost-guard” setting and simply left to get on with the job, should take care of this problem once and for all. However else you heat your greenhouse, it is probably worth considering having one of these handy heaters on stand-by – they really are invaluable greenhouse aids as the weather cools down.


Condensation can be a major problem and it is unfortunately one which, at least at certain times of the year, is almost impossible to avoid entirely. Damp surroundings and still air offer perfect conditions for many mildews, moulds and other fungi to develop, especially the likes of grey mould (Botrytis), so again, ensuring good ventilation is a key part of reducing the risk of problems developing.

Insulating the greenhouse during the cooler weather and trying to remove any obvious causes of condensation – though this is not always easy – can often also be worthwhile. One cause which is often overlooked is the use of bottled-gas or paraffin heaters in the greenhouse – these fuels produce water vapour when they burn. Since they are obviously used more when the weather outside is cooling the greenhouse glass the most, something of a vicious circle can develop without adequate ventilation – however counter-intuitive it may seem to open windows in the depths of winter!

Greenhouse Management

Trying to do too many competing things in a single greenhouse inevitably leads to problems, but it can often be difficult to know exactly how things are going to develop – or your own interests change – in time. This is something which can often catch out the new greenhouse owner in particular, though a certain amount of planning at the outset can help avoid obvious pitfalls. Selecting too small a design is one of the most common of these, so consider buying one which can be extended and site it somewhere with enough room for expansion if you do find you need more space. If you cannot simply extend your present greenhouse – or you need two quite different types of growing environment, you can always get a second one or perhaps see if either a conservatory or garden frame could meet your needs as an alternative.

Providing adequate storage for equipment which allows things to remain accessible but tidy can be difficult, especially in the smaller greenhouse. While making use of all the space below staging makes a lot of sense, it is important to remember the amount of water that will be around. Water-proof boxes are pretty much essential for anything which may rust or be spoiled and secure storage is, of course, a must for pesticides and the like, particularly around children or pets. It is an important issue, since lack of properly organised storage space can itself lead to other problems – not least because a greenhouse which is difficult to keep clean provides the perfect breeding ground for pests and diseases, allowing them to hide away unseen.

Every aspect of gardening has it own particular set of potential snags and hazards for the unwary and the greenhouse is certainly no exception. Fortunately addressing these potential trouble-spots before a problem does develop should help ensure that nothing spoils your enjoyment for too long.

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I've just brought an old house with a greenhouse in the garden. It's not been touched for ages I turned it the other day and was really dusty and smelt horrendous. Like death if I'm honest. Can anybody shed light on this and what to do.
Jay - 19-Jul-17 @ 8:21 PM
The leaves on my greenhouse plants ( predominantly chillies) have white spots on them. Does anyone know why? Am I,perhaps,overwatering? All advice appreciated.
Jo - 17-May-17 @ 6:44 PM
Hi my green house has a strange eggy smell that I smell on occasion anybody know what this could be?
Michelle - 10-May-17 @ 7:11 PM
i live in kashmir.i have a green house there are some problems of plants like plants are dry,the leaves are dry......i am trying such medecine...but the problem are not solve....these plants namely chilly plant ets
Danish - 28-Mar-17 @ 4:56 AM
just as someone else stated, I have a problem with the top of soil turning green.What do I need to do to prevent this and get rid of it?
becki - 7-Apr-12 @ 9:51 PM
I have set my bedding plant seeds in trays and placed them on shelves in my greenhouse. Overnight I have found the seeds dug up and have had to reset them. I have place fine mesh netting over the automatic window vent and installed an electronic rodent repellant device but the seeds are still being dug up. We have a neighbour with a garden pond and get frogs in our garden. Could these be the culprits and how do I get rid of them?
Harry - 4-Apr-12 @ 10:00 AM
hi i am a new greenhouse grower i have a problem with the top of soil going green can you help kind regards
not known - 16-Feb-12 @ 12:16 PM
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