how much does a bag of compost fill?

londonTiger

Sounds like a daft question. But I'm trying to work out how much soil I need for my planters. I got 2x 125L bags of compost from b&q. It looks like it would fill 2 of my planters, but is the soil compacted in the bags so therefore likely to expand. Or does fill the same volume outside of the bag as it is in the bag?

londonTiger

second question, is a 100% compost planter suitable or does it need to be mixed with regular soil?

wellused

The compost will expand but then again it will settle after time and weather so the answer is probably no, compost only beds are ok but will tend to dry out quicker than the soil so adding good quality topsoil is the best option in my opinion.

I_have_spoken

second question, is a 100% compost planter suitable

Depends on what you intend to plant, you'd probably be OK for annuals or leaf veg crops. Anything else, and I'd be add some loam/grit/vermiculate/water gel

londonTiger

it's mainly annuals, brassicas, pumpkin, marrow, beans.

I will put a plastic container at the bottom of the planter before filling with soil, so that water doesn't run through and dry up the soil.

I can then layer the top 1-2inch with topsoil. Loam is so expensive and hard to pay in small quantities it seems wickes does not sell loam in small bags but only in tonne bags.

Dizzy_Ditzy

You'll need to make sure your plastic container has drainage holes in, or put some "crocks" at the bottom to help with drainage

Your brassicas will like firm soil so make sure you firm well up around them

londonTiger

queen_of_cheap wrote: »

You'll need to make sure your plastic container has drainage holes in, or put some "crocks" at the bottom to help with drainage

Your brassicas will like firm soil so make sure you firm well up around them

The planter is 30cm deep, I was planning on putting 1x 10cm tall plastic tub inside the planter to act as a water reserve at the very bottom so that the planter doesn't ever fully dry out.