I've built a sizeable raised planter (8 x 0.5 x 0.5m) that's essentially just a frame sitting on the lawn, without a bottom. I'm looking for the best way to fill it up since I'll be planting a rose bush and some tulips. I've seen a lot of different opinions in various forums, so I want to gather some insights here.
Should I add gravel or rocks at the bottom, or is it better to mix in perlite? I'm also considering using slow-release compost, but how much should I use? Since the base is just grass, I've added some excess lawn dirt from landscaping, but there's still a lot of grass. Would laying down cardboard or newspaper help prevent grass from growing through, given that there'll be 40cm of soil on top?
Also, I've seen ready-made planter soil bags with nutrients and drainage grit costing around £80-100 for about four bags. Would that be a good option to use by itself? I appreciate any advice you can share!
5 Answers
What are you planning to grow and what’s your budget? If you can buy a bulk bag of compost and topsoil, that would be ideal. Keep in mind that there’s usually a 30% decrease in volume when it settles, so buying extra is smart. If you have any compostable materials, filling the bottom with those is great for long-term health. However, I'd avoid adding gravel if it's resting on grass.
You’ll have plenty of leaves to mix into your planter this time of year. Just make sure to plan based on what you want to grow; some plants thrive directly in the ground without the extra costs of a raised planter! But if you’re set on the planter, consider how it may create moisture issues for nearby fences.
I hadn’t thought about moisture affecting the fence; that’s a good point!
Don’t overthink it. Any basic topsoil or compost will provide enough nutrients since it won’t be compacted. Once you fill it, the grass won’t grow back through the soil, so there's no need for cardboard. You might want to check local groups like Facebook or Nextdoor for any free topsoil people might have.
Cheers, I’ll look into that!
For my planter, I just cut off the top layer of grass, flipped it over, and mixed in some garden compost along with small branches, twigs, and topsoil. I then used a cubic meter of a mix called Denise's Delight, which is topsoil combined with rotted horse manure. It turned out to be super cost-effective to buy in bulk. Just make sure you're not introducing too much green material that could sap nitrogen!
Thanks! Unfortunately, I'm on a new estate, so there's not much local plant material to work with.
Don't worry about the grass. It’ll die under a layer of soil, so no need for cardboard—just go with a couple of bulk bags of material!
Cheers for the reassurance!
Thanks for clarifying! I lined the planter already; it's pressure-treated wood, so I hope it'll last a while.