Compost/Soil for new raised beds on concrete

[Dan]

Hi

I'm about to build a number of raised beds on a concrete surface. They will be primarily used for growing vegetables.

I'm going to need around 1 cubic metre of soil/compost and am trying to figure out what is the best stuff to go for - someone suggested spent mushroom compost but I've also read lots of other contrasting ideas.

Any help or advise - including suppliers - would be gratefully received.

Also, is there anything else I need to be careful of - bearing in mind that I'm siting these on a concrete base?

Thanks in advance,

Dan

[POTHEAD]

Originally Posted by Dan

Hi

I'm about to build a number of raised beds on a concrete surface. They will be primarily used for growing vegetables.

I'm going to need around 1 cubic metre of soil/compost and am trying to figure out what is the best stuff to go for - someone suggested spent mushroom compost but I've also read lots of other contrasting ideas.

Any help or advise - including suppliers - would be gratefully received.

Also, is there anything else I need to be careful of - bearing in mind that I'm siting these on a concrete base?

Thanks in advance,

Dan

hello dan
the first problem i think you have to look at is drainage,maybe drill or break up the concrete first
regards pothead

[Dan]

Thanks for that.

I have thought about drainage and whilst a small area on my patio does puddle after very heavy rain, the area I'm planning on putting the beds doesn't.

With raised beds generally draining well anyway, I'm hoping that things will naturally be okay - I'm thinking that water will either naturally be held within the soil (as would happen on any base) and any excess would kind-of seep out under the wooden bed edges.

Am I being overly optimistic or missing something important?

[Lesley Jay]

Hi Dan, do you think that some of the compost might seep out from under the bed edges when watering? It's just a thought. Maybe the raised beds need lining with a membrane which would keep the compost in place.

As raised beds aren't usually very deep why not use a combination of raised beds and containers or pots for the deeper rooting veg. Here's a couple of links for compost and spent mushroom compost.

UK Compost

Spent Mushroom Compost (1 m³) Suppliers. Buy Today, Free UK Delivery

[Dan]

Thanks for the reply Lesley Jay,

I had planned on putting a weed suppressing membrane down covering the base and sides of the beds. They will be about 8 inches (20 cm) deep so should be okay for most veg. Things like carrots I will simply seek out fatter, shorted varieties and grow them.

As for compost - is 100% spent mushroom compost a good idea? There seem to be lots of options and I can't really figure out what's best.

[Lesley Jay]

I would mix compost with top soil as this aids water retention. Top soil can be pretty expensive and you really need screened top soil that has all the stones removed. Sterilized top soil has all the weed seeds killed off.

[DunDiggin]

Buy topsoil. Compost is too light and spent mushroom compost is just a soil improver. Buy your soil by the tonne (1 tonne should be approximately 0.8 cubic metres). Expect to pay about £50 for a decent quality.