I have a long rectangular planter basket on the side of my house. Pre-shaped liners (like these ones*) don’t seem to come in the right size for it, so I buy coco fibre fabric by the sheet and cut it to size. It’s available from some of the big box stores, from Amazon*, and my local nursery used to sell it by the yard before they closed down) and cut it to size. I didn’t love the way it turned out the first time or two, but after a decade of practice I’ve finally figured out how to do it right. The piece I purchased was 36″ x 36″.
To start with, I centered the sheet of coco fibre on the basket, pushed it down all the way to the bottom, and then started to shape the corners. Essentially, it’s like wrapping a birthday present, except doing it from inside the box instead of outside.
I try to keep the fabric flat against the basket frame, with no bunched up pieces. Folding produces a much neater result than gathering.
In the picture below, of the left hand side of the planter, you can see that I’ve wrapped the fabric from the back of the planter (the back is on the right of the photo) towards the front (where my hand is). Then I’ve taken the fabric from the front and folded it towards the back.
The idea is to keep these thicknesses of fabric flat against the left edge of the planter. The overlap ensure that soil will not escape.
With this rough shaping in place, I can now trim off any big flaps of extra fabric. This is not the final trim–I leave a lot of extra/margin. This trim is just to make it easier to handle the liner as I refine the shaping in the next steps.
Next I fill it with soil, to near the top of the basket, pulling the fabric into place as I go. I use the weight and bulk of the soil to help anchor the liner fabric in place. I keep adjusting until I have nice crisp corners and the fabric fully fills the planter (i.e. it’s puffed out right to the edge of the planter frame, not pulled so tightly that it’s like a too small liner in an oversized basket).
To further test the fit, and ensure that no gaps are going to open up and empty out all of my soil during a big rainstorm, I water the planter really well.
This isn’t just a light watering, this is watering until it literally drips out of the bottom of the planter. I want to know about any gaps now, before I trim the liner and put my plants in, than later when it’s too late to fix.
With the soil now heavy and wet, I take another look to see if there are any bulges in the liner, or places where I need to push the liner out more to really fill the basket. I won’t lie, it’s messy to play around with it at this stage but I think it’s the best way to finesse the fit. I focus most of my attention on the corners as they’re the most difficult to get right.
Once I’m satisfied that the liner fits as well as possible, I trim the excess fabric off the top. I cut all the way around, being careful not to cut too short so that the liner dips below the edge of the basket frame. My goal is to leave about 1 cm, or half an inch, sticking up.
Don’t worry if it the edge isn’t perfectly straight; plants will cover it soon enough. Because I have this planter against my house, and because the AC drips into it (read about my self-watering planter here) I leave the back edge of the liner a little higher. This helps keep soil and moisture in the planter and not up against the bricks of my house where the moisture could do damage.
And that’s all there is to it. The planter is ready to be planted!
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