It's usually said you can grow tomatoes in greenhouse borders for two or three years, but then diseases build up and you need to switch to pots or growbags. Theoretical question: does anyone know how long the greenhouse soil can be left fallow before you plant again. (At my last house I followed this advice and grew tomatoes in pot for many, many years. It was only in my last year there that I went back to growing in the border, and it was fine.)

If one could safely sterilize the ground I think one could use it repeatedly. The issue is how to sterilise, chemicals would not be good and there are no amateur systems I'm aware of.

Many years ago I worked at a cut flower nursery one summer.
They grew the same chrysanthamums (?) in the ground from seedling to cutting height, repeatedly throughout the year.

After taking each crop the long four foot beds were covered in heavy duty black plastic, held down along the edges, one end left unsealed while the othe was put over a frame and sealed around the steam hose from the ex-navy boiler. The bed was then steamed overnight (may have been longer) then allowed to cool to a safe temperature and dismantled, forked over with a sprinkle of fertiliser and replanted.

This was done by the manager and two of the full time chaps, we student types were kept clear as scalds are unpleasant.

Not sure if a domestic equivalent could be engineered from a wallpaper stripper, they only seem to have an hours worth of water supply.

One of the guys on our site removes his soil out of his greenhouse every other year and replaces it with a mix of soil and home-made compost. He always has a good crop from his 8x6 greenhouse. I did this last year and everything was good, but it is a lot of hard work, digging in confined areas Jane

I have a border each side of a central path and simply grow Tomatoes on alternate sides with a mixture of things the other year. I add bagged composted manure and fertiliser each year. They don't seem to mind, this is the tenth season.

Thanks, all. I think I'll give the idea of steam cleaning the borders a miss! Geoff, when you say you plant the other border with a mix of other things, what do you have in mind? Peppers and aubergines are an obvious choice, though I think both are in the same family as tomatoes, though not as prone to disease. But your solution sounds good.

Yes to Peppers, tend to grow Aubergines in pots in a smaller greenhouse that I heat earlier in the year. It is a big greenhouse so the alternatives also include a block of Sweetcorn, Carrots and some Cobra beans. Some early salad precedes the Sweetcorn.

Wow, yes, Geoff - distinctly bigger than my new, 6x6 baby. But I think your approach of using a border on alternate years could work for me. Thanks for that.

I have read your post which is very useful to me also because I have big greenhouse and confuse that what planting in my greenhouse border. After reading this post definitely I will try planting Sweetcorn, Carrots and some Cobra beans. Thanks you very much.