Changing soil in greenhouse borders

by Pippa Greenwood

I must confess that I don't refresh the soil in my greenhouse as often as I should (or as often as I might be heard to advise if, say, I was asked the question on Gardeners' Question Time...)

Close-up of a gardener holding a greenhouse tomatoIt can be much trickier changing the soil in a greenhouse trench than in a garden border. I’m lucky to have trenches with brick bases, but my heart goes out to anyone with borders glazed to the base. It's so easy to break panes when excavating soil.

I must confess that I don’t refresh the soil in my greenhouse as often as I should (or as often as I might be heard to advise if, say, I was asked the question on Gardeners’ Question Time…). It’s such a tedious job – almost as tedious as cleaning behind the cooker.

If I had sufficient space and enough greenhouses, I would love to conduct a trial to determine how long soil could be left before plant growth was adversely affected. As both a gardener and a plant pathologist, I’m keenly aware of the problems that can arise when soil-borne pathogens accumulate. I’m not sure how conclusive such a trial could be, as experience has taught me that so many other factors affect plant growth, and conditions vary so dramatically from year to year. But it would be fascinating to monitor how long the soil could be left without affecting yields of crops such as tomatoes.

Meanwhile, I think I’ll just replace the top 20cm (8in), which will hopefully be sufficient for the tomatoes I'm about to plant...

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Gardeners' World Web User 06/04/2011 at 14:26

I used to have a 40ft by 8ft greenhouse when i was feeding the nine of us from the garden,veg. and eggs from chickens and ducks and I cultivated the 3ft wide borders either side of the path as i would outside i.e. by rotating the crops so as not to deplete the soil of essential minerals. That and plenty of cow or horse manure gave me magnificent crops for over 20 years and saved me lots of money and trips to the shops. It was a forcing greenhouse from s nursery which closed down and sold its land for housing and so the bottom was brick built. It cost my husband £40 and the dismantling and removing from the site, then he had to build it for me. It paid for itself three times over in its first year and I was winning prizes for dwarf beans etc. at horticultural shows as it was a forcing house! Your trial would be interesting but not wise as , when your crop takes goodness out of the soil you must replace it. Better to give the tomatoes a rest for a year(grow them outside) and grow beans whose nodules will put nitrogen back into the soil.

Gardeners' World Web User 06/04/2011 at 22:53

So how often should we change the soil?

Gardeners' World Web User 07/04/2011 at 18:01

I grow my Tomatoes in large pots outside in compost of my own mix, and get good crops. This year iam using the same pots and soil. wish me luck/ Bettall

Gardeners' World Web User 08/04/2011 at 12:40

I grow my tomatoes in gro-bags in the greenhouse, so no problem in having to change the soil, and I always get a fantastic crop.

Gardeners' World Web User 11/04/2011 at 17:43

i grow my tomatoes in pots with grow bag compost, what should i do with the compost after the tomatoes have finished growing?

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