Raised bed soil

bac2ari · October 2023

Hi, I’ve bought 3 large steel planters to use as raised beds (see photo - looks awful at the mo!). They are a meter wide and varying heights. Want to fill them with some evergreens and a few perennials (none of my chosen plants will have special soil requirements, going for unfussy options). What should I use to fill the rings up with? I have some bags of new top soil, should I add compost two & mix it all up - and if so what kind, a general one or a John Innes type one for more permanent plantings? The area am putting the rings on was previously a jungle of thistles which I’ve chopped away. Am needing to get rid of excess soil to flatten the area - could I use some of the soil in the rings or am I just setting myself up to get thistles in the rings? The soil doesn’t seem great really, the planting area is right under a very tall pine tree. Any advice would be appreciated with what to use to plant into. Sorry for such a long post.

nick615 · October 2023

Yes! I think you'll transfer seeds with the soil. Heavy duty cardboard laid underneath each planter will help deter roots penetrating from below, but I think your main task will be keeping the soil moist. I tried a similar venture using large tractor tyres which I had to water very regularly. Your tree will take much of the water from the soil and any form of RB can raise its soil above the surrounding level.

Fairygirl · October 2023

I agree that it wouldn't be a good idea if there are perennial weeds, although any weed can still seed into the beds.
No matter what you're planting, the soil mix will have to be reasonably moisture retentive, because they will drain more readily than the ground does. It would be the same as planting into the ground in that respect - you use a mix that suits the plants. I'd use mostly soil, with some compost [any kind will do] mixed in. If you're using perennials which like good drainage, that should be fine, but you may want some fine gravel mixed through as well.
Like any raised bed, you'll have to top them up on a regular basis, so be careful when planting - make sure the level the plants are in the pots is around an inch from the tops of them, and no lower, as that can be a problem later on when the soil drops.

It also depends on your climate as to watering in future. Although those are large, they will still need watering if you don't have adequate rainfall through long dry periods, especially for shrubs or trees which are establishing. Easier when plants are smaller though, as water can get through.
I rarely water anything in my raised beds because of the climate here, but it's the initial stages, when plants are establishing, that matter most.

Raised bed soil

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