The short answer: a coir hanging basket liner is a mat of coconut husk fibre, bonded with natural latex or by needling, that sits inside an open wire basket and holds the compost in. Measure the basket across the rim and from rim to base, buy a moulded liner that matches both numbers (or a flat sheet you cut to fit), and put a sheet of plastic with a drainage hole inside it if the basket dries out too fast. Expect two to three seasons from a liner before the base thins and needs replacing.
Key facts
- Moulded liners come in standard rim diameters, most often 12, 14, 16 and 18 inches (30, 35, 40 and 45 cm). A 14-inch round liner usually fits a basket 6 to 7.25 inches deep.
- Between two sizes, go up. The fibre settles and pulls in as it wets.
- Coir and moss baskets lose water through the sides as well as the base, so they dry faster than a solid pot. In hot weather they can need water every day.
- A plastic inner layer with a hole in the bottom cuts the loss through the sides. Water-retaining gels help for the first few weeks only.
- Liners usually last two to three outdoor seasons. The base goes first because it stays wet longest.
What a coir liner is made of
Coir liners are made from the long, stiff fibre of the coconut husk, the bristle and mattress grades rather than the fine pith that goes into growing media. The coconut fibre grades guide explains how those grades are separated. What matters for a liner is that the fibre is long enough to interlock and rich enough in lignin to resist rot for more than one summer.
There are two ways to turn loose fibre into a mat that holds its shape.
| Construction | How it's made | What you get | Trade-offs |
|---|---|---|---|
| Latex-bonded (rubberised) | Fibre is laid in a layer and sprayed with natural rubber latex, then pressed or moulded and cured | Stiff, self-supporting liners that hold a bowl, cone or trough shape | Firm and tidy on the shelf. Only fits the basket shape it was moulded for |
| Needle-punched (needled felt) | Barbed needles push the fibres through each other until the layer locks together, with no binder | Flexible sheets, rolls and discs | Easy to cut and fold. Doesn't hold a shape on its own, so it relies on the basket frame |
Some liners combine the two, a needled sheet with a light latex spray. Others have a thin layer of plastic sandwiched between two coir layers, built in to slow water loss through the sides.
Moulded liners versus flat sheets
| Moulded (pre-formed) | Flat sheet or roll | |
|---|---|---|
| Fit | Drops straight into a standard round, conical or half-round basket | Cut to fit anything, including odd shapes and very large baskets |
| Thickness you'll see | From about 10 mm up to 15–20 mm on thick mat types | Roughly 3 to 6 mm on many rolls |
| Look | Smooth, even edge | Shows pleats and overlaps until plants cover it |
| Best for | Standard baskets, retail sets, replacement liners | Mangers, odd-shaped planters, bulk use |
Published thickness and weight figures vary a lot between makers. One latex-coated roll is listed at 800 g per square metre and about 6 mm thick, while thick moulded liners run to 1.5–2 cm. Treat thickness and weight as things to specify, not things to assume.
How to measure a basket for a liner
Measure the empty basket, not an old liner.
- Diameter: measure straight across the top, rim to rim, through the centre.
- Depth: measure from the rim straight down to the lowest point of the base.
- Shape: note whether it's a round bowl, flat-bottomed, conical, a half-round wall basket, or a trough or manger.
Then match both numbers to the liner. Diameter alone isn't enough. Two 14-inch baskets can differ by more than an inch in depth, and a 14-inch conical basket can be well over twice as deep as a round one. Wall baskets and hayracks need their own liners, because a round liner won't sit flat against a wall.
| Rim diameter | Liner to buy | Rough compost volume (full hemisphere) |
|---|---|---|
| 10 in (25 cm) | 10 in | about 4 litres |
| 12 in (30 cm) | 12 in | about 7 litres |
| 14 in (35 cm) | 14 in | about 11 litres |
| 16 in (40 cm) | 16 in | about 17 litres |
| 18 in (45 cm) | 18 in | about 24 litres |
The volumes are geometry for a half-sphere, so a shallower basket holds less. For planting, three plants from 4-inch pots suit a 10 to 12-inch basket, and three or four suit a 14-inch one. Bigger baskets dry out more slowly because there's more compost per square centimetre of exposed side. If you keep having to water twice a day, go up a size.
Cutting a flat sheet
A flat sheet has to cover the curved surface of the bowl, which is larger than the circle across its top. For a round, hemispherical basket, start with a circle about one and a half times the rim diameter. Lay it centred over the basket, push it down into the base, and cut four to six short slits in from the edge so it can overlap and lie flat against the wire. Trim the top so a little stands proud of the rim. It shrinks back as it settles.
Why coir-lined baskets dry out
A plastic pot loses water from the compost surface and through the drainage holes. A wire basket lined with coir loses it from the whole outer surface as well, and wind blowing past a hanging basket speeds that up. Lined wire baskets dry fast, and they dry faster as the season goes on and the roots fill the compost.
For a sense of scale, 5-litre baskets of petunias have averaged a daily water use of 142 to 380 ml per basket, and each basket used less than 25 litres over nine weeks. When watered from the top, 30 to 70 per cent of the water applied to wet compost ran straight through. Self-watering baskets with a reservoir wasted less than 7 per cent. Doubling the water given to hand-watered baskets only added 8 to 15 per cent more flowers. Water slowly, until the first drips appear, and stop.
Adding a plastic inner layer
The cheapest fix is a sheet of plastic between the coir and the compost.
- Use any thin plastic sheet or bag. Black blends in better than white or clear.
- Cut a drainage hole in the middle of the base. Practical advice ranges from a few punched holes to one hole as wide as 6 inches (15 cm). The larger hole is safer, because a basket that can't drain is worse than one that dries.
- Lay it in the liner, add a scoop of compost to hold the hole open, then fill.
- Trim the plastic so about 1 cm stands above the compost. This lip holds water on the surface instead of letting it run off the edge.
If you want to plant through the sides, cut the plastic at the same points as the coir. Liners with a plastic layer already built in save you this step.
Water-retaining gels
Polyacrylamide gels do hold extra water, but the benefit is short. In hanging-basket trials the gel lengthened the gap between waterings at the start of the crop. Within about three weeks most of the effect had gone, because fertiliser salts shrink the gel and the mix compacts. By the end of a 100-day crop, baskets with the highest rates needed watering more often than untreated baskets, and plants in mixes with a sixth or more gel by volume produced fewer flowers. The realistic gain for a finished basket is well under a day between waterings. A bigger basket, a plastic inner layer and a mix that holds water well all do more.
For the mix itself, a light potting compost that drains freely is right. A coir-based mix with some perlite works well in baskets because it rewets easily. See coco coir for container growing for blends and feeding. Add a controlled-release fertiliser at planting, or feed with liquid fertiliser every two weeks.
Planting through the sides
Side planting isn't essential. Strong trailers planted round the top edge will hang down and hide the sides, usually within about a month. Side planting just makes the basket look full sooner.
- Cut slits or cross-shaped holes in the liner at varying heights, no lower than 10 cm above the base.
- Fill with compost up to the level of the holes.
- Wrap each young plant's root ball in a twist of newspaper, or feed the shoots through from the inside, and ease it through the hole.
- Cover the roots with more compost and firm gently.
- Plant the top, trailers around the edge and taller plants in the centre. Leave the compost just below the rim.
Keep holes small. Every cut is another place for water and compost to escape.
How long a coir liner lasts
Most liners give two to three growing seasons outdoors. Replace one when you see:
- thinning or bare patches, often first at the base
- compost washing out through the sides when you water
- gaps opening between the liner and the frame
Empty the basket at the end of the season, let the liner dry, and store it out of the rain to get the third season. A plain fibre or fibre-and-latex liner can be torn up and composted. Liners with a built-in plastic layer can't, so strip the plastic out first. Coir fibre is slow to rot, which is the same property that makes coir fibre mats and tree discs useful as mulch.
Wall troughs, mangers and window boxes
The same rules apply to long containers. Trough and manger liners are sold in lengths such as 60 cm, 36 inches and 48 inches. Measure length, width at the top, width at the base and depth, because trough fronts are often sloped. A plastic inner layer is just as useful in a wall manger as in a basket, since one face is exposed to sun and wind all day.
What retail and nursery buyers specify
If you're buying liners for a garden centre range or for a nursery that plants up baskets, these are the points to pin down with a supplier:
| Specification | Why it matters |
|---|---|
| Shape and size: rim diameter, depth, and profile (bowl, flat-bottomed, conical, half-round, trough) | Liners must drop into the frames you sell or plant, without trimming |
| Thickness and weight per piece (or g/m² for rolls) | Thicker, denser liners hold more compost and last longer, and weight is the easiest check on consistency between shipments |
| Construction | Latex-bonded for shaped liners that stand up on a shelf, needle-punched for rolls and flexible sheets |
| Colour and appearance | These sell on looks. Even colour and fibre free of pith and dust matter more than for most coir products |
| Built-in plastic layer or not | Reduces watering complaints, but adds cost and plastic |
| Packing | Moulded liners nest, so stack count per carton decides freight cost |
Ask for a sample of each size and check it against your frames before ordering in volume.
CVM Fiber and Industries in Kanyakumari, Tamil Nadu, India produces coir bristle fibre, the long fibre grade liners are made from, along with coco peat and custom products. If you're sourcing fibre or want to talk through a specification, get in touch.
FAQ
What size coir liner do I need for my hanging basket?
Measure the basket across the top from rim to rim, then from the rim straight down to the base. Choose a liner that matches both measurements, not just the diameter. If you fall between two sizes, take the larger one, because the fibre settles and draws in as it gets wet.
Should I put plastic inside a coco liner?
Yes, if the basket dries out quickly. A thin plastic sheet between the coir and the compost cuts the water lost through the sides. Always cut a drainage hole in the base, and leave a small lip of plastic above the compost to hold water on the surface.
Which way up does a coco liner go?
Moulded liners only fit one way, with the smooth or shaped face outwards against the wire. Flat sheets often have a smoother face and a rougher one. Put the neater face outside, where it shows, and the rougher face towards the compost.
Why does water run straight out of the sides of my basket?
Coir is porous, so water that hits dry compost or the liner itself runs through the sides instead of soaking in. A plastic inner layer stops most of it. Watering slowly with a fine rose, and stopping at the first drips, wastes less than a fast flood from a hose.
How long do coco basket liners last?
Usually two to three growing seasons outdoors. The base wears out first because it stays wet longest. Replace the liner when it thins, when compost washes out through the sides, or when gaps open between the liner and the frame.
Can I reuse a coir liner next year?
Yes, if it is still thick and intact. Empty it at the end of the season, knock off the old compost, let it dry and store it under cover. If the base is thin, put a plastic layer inside or replace it.
Are water-retaining crystals worth adding to a hanging basket?
Only for a short time. Gels hold extra water when a basket is first planted, but fertiliser salts shrink them and the effect fades within a few weeks. A larger basket, a plastic inner layer and steady watering do more over a whole season.
Is a coir liner better than moss?
Both let water escape through the sides, so a basket dries out faster with either than a solid pot does. The practical difference is fitting. A moulded coir liner drops straight in, while moss has to be wetted and packed in by hand to form a pocket for the compost.