Greenhouse growing on clay.

[BigShot]

I know most greenhouse type questions have probably been asked and answered about a thousand times already, but my search-fu is weak and I can't find what I need to know. Sorry.

Greenhouse on its way this weekend. I'm just heading out to level the ground it'll be on but as it's on clay I'm unsure how best to proceed once it's level.

Aside from uncertainty about whether to lay a few courses of bricks to raise the greenhouse a bit giving more bedroom, the main issue is how to grow in there.
I'm not made of money so I was initially leaning away from buying in tons of compost every year to grow in pots, but as the soil is clay I'm not sure what to do now.

I thought about digging out the clay to a depth of 1 spit, backfilling with something better (maybe manure, compost and/or topsoil. Obviously that would mean needing to replace or sterilise the soil regularly though.
Then there's improving the clay with leaves, compost, grounds, manure and so on. Still has disease issues but no need to buy anything in. (I have a near endless supply of horse manure and leaves are free every autumn.)
Then there's raised beds on clay, raised beds on improved clay and so on.

Quite frankly, I'm stumped.

Any suggestions or good links/resources I can read?

[chris]

I was going to suggest pretty much what you've suggested to yourself heh. Growing in the borders will be cheaper and easier to maintain your plants (less watering - in pots, in thesummer you'll need to be able to water them at least twice a day on hot (heh) days). It's really a personal choice.. I decided to grow in pots as I'd already dug a huge amount of earth out to get the site level for my greenhouse - and I knew I'd not want to dig the borders out each year. Pests are also an issue with growing in the borders.. I have a load of snails and slugs around my gardens so I didn't want that hassle either.

You probably know but clay is excellent at holding onto the nutrients in the ground.. so it's a double edged sword really.. improve the clay [by whatever means] and end up having to replace it - but watering required will be less, or go for a solid(ish) base, and grow in pots, but have to buy compost (or make a lot of your own, leaf mould, mix in with everything else you can get your hands on etc) in to grow in the pots! - and then water a lot

Hard to advise really... I just thought about the long term crops I wanted to grow in there, bought an automatic waterer and stumped up for a gravel + slab base.

[chris]

Oh aye, and in this forum you'll find many posts about borders vs pots, etc - but i'm guessing you've already had a read of them and you're still stumped?

[BigShot]

I've read a fair bit about borders vs pots, yes. It's the specifics of greenhousing with clay that has me stumped.

Growing in borders appeals to me thanks to reduced watering. I think I'll probably start with the borders and move to pots at a later date if they become a hassle. By then I'll probably have the funds for some sort of auto-watering too.

Now I just need to figure out if I'm getting rid of the clay entirely or improving it with a load of organic matter.

[King Carrot]

I've read a fair bit about borders vs pots, yes. It's the specifics of greenhousing with clay that has me stumped.

Growing in borders appeals to me thanks to reduced watering. I think I'll probably start with the borders and move to pots at a later date if they become a hassle. By then I'll probably have the funds for some sort of auto-watering too.

Now I just need to figure out if I'm getting rid of the clay entirely or improving it with a load of organic matter.

That's what I'd do year by year and it sounds like you have access to "safe" non contaminated manure. Meanwhile if it was me, I'd just dig a large hole for anything I was planting and load it with a mix of manure, soil and fertilizer and plant in to it.

[womble]

I've read a fair bit about borders vs pots, yes. It's the specifics of greenhousing with clay that has me stumped.

Growing in borders appeals to me thanks to reduced watering. I think I'll probably start with the borders and move to pots at a later date if they become a hassle. By then I'll probably have the funds for some sort of auto-watering too.

Now I just need to figure out if I'm getting rid of the clay entirely or improving it with a load of organic matter.

I agree with king carrot above.

Bigshot, I was in your position exactly a few years ago. I also have access to large amounts of manure and leaves. The soil in my GH was unworkable.
I'd already decided to go for border growing as I hated growing in pots or growbags. It's so variable and when I started growing in the soil the change in yield was massive.

So I improved the GH borders massively, took out some soil and introduced large amounts of very well rotted manure, alot of leaf mould compost and HM compost.
Every 2 years (done it once) I intend to dig out the border and swap it with a raised bed's soil in the garden. It's quite easy and doesn't take very long.

Hope that helps, I found it to be the best way. Oh and I dug down into the GH soil and had removed some subsoil, to get the surface at a low level, it gives a bit more headroom for growing.

[Kristen]

I dug the (clay) soil out of my greenhouse borders and use a mixture of rotted manure and home made compost. Its pretty "rough" when it goes in, but nice and fine by the end of the season, where it then goes on other beds (which won't have Potatoes, or have just had Potatoes). The compost is pretty light to swap in & out (compared to trying to dig / barrow the clay ...). But as an alternative to changing the soil you could use grafted plants where the root-end has been chosen to be resistant to disease.

I have grown in pots, bags, ring-culture etc. over the years and prefer growing in the border. They will go a couple of days without watering, whereas with pots I used to water twice a day.

I lowered my beds in the process. Raised beds means less cropping height (as does pots, and to a lesser extent bags - if you lay them flat). I wish I had dug them out before building the greenhouse - the clay was hard as rock when I did it in the Autumn after a season growing in pots