Polybag Nursery & Bags & Potting Media
Raises forest
Enter target plants, a mortality buffer and bag size to see how many poly bags you needand the potting media — litres per bag, total litres and cubic metres — for your nursery.
Plan your polybag nursery
Next: fill 1,100 bags and arrange about 1,037 L (1 m³) of potting mix — typically a soil : compost : sand or cocopeat blend.
Volume assumes ~80% fill of each bag; actual media depends on settling, compost density and how full you pack. Order a little extra.
Polybag nursery — key facts
- Per seedling
- one poly bag
- Bags
- plants × (1 + buffer)
- Buffer
- ≈ 10–20% for losses
- Media per bag
- set by bag size
- Total media
- bags × litres per bag
- Mix
- soil + compost + sand
- 1 m³
- = 1000 litres
- Privacy
- Runs in your browser; nothing uploaded
Fill enough bags — and enough media — in one go
Forest, plantation and horticulture seedlings are raised in poly bags filled with a potting mix of soil, compost and sand. The two things you must get right before you start filling are how many bags to prepare — your target plants plus a buffer for the seedlings that die — and how much media to mix, which depends on the bag size. Run short on either and you stall mid-season with half-filled benches.
This tool gives the polybags needed, media litres per bag, total litres and total cubic metres from your target plants, mortality buffer and bag size. Use it to order bags, mix or buy the right volume of media, and budget the nursery before the first bag is filled. Pair it with the Vegetable Nursery Tray, Grafting Success and Transplanting tools to plan the whole raising-to-field sequence.
Order enough bags
Target plants plus a loss buffer.
Mix the right media
Litres per bag and total volume.
Budget by m³
Convert media to cubic metres to buy.
Any nursery
Forest, plantation or horticulture.
Frequently Asked Questions
What is a polybag nursery?+
Forestry, plantation and horticulture seedlings are commonly raised in poly bags — black polythene bags filled with a potting medium. Each bag holds one seedling until it is big enough to plant out. Bags make handling, watering and transport easy and give every seedling its own root ball, so it transplants with little shock.
How many polybags do I need?+
You need one bag per seedling, plus extra to cover seedlings that die or fail to reach size. Bags = target plants × (1 + mortality buffer). For 1000 plants with a 15% buffer you'd fill about 1150 bags. The calculator works this out so you fill enough in one go and aren't short at planting time.
Why add a mortality buffer?+
Some seeds won't germinate, and some seedlings die or stay too weak to plant. If you fill exactly your target number of bags you'll fall short. A buffer — often 10–20%, more for difficult species — covers those losses so you still have enough plantable seedlings to meet your target after the weak ones are culled.
How much potting media will I need?+
Media per bag depends on bag size — a small bag might take half a litre, a large one several litres. Total media = bags × litres per bag. The calculator gives litres per bag, total litres and total cubic metres so you can order or mix the right amount of soil, compost and sand.
What goes in the potting mix?+
A typical nursery medium is a blend of topsoil, compost or farmyard manure, and sand, often around 2:1:1, adjusted for drainage and fertility. Forest nurseries may add leaf mould or coir. The aim is a light, free-draining, fertile mix that holds moisture but doesn't waterlog the bag.
Does bag size matter?+
Yes — bag size sets both the media per bag and how long a seedling can stay before it gets pot-bound. Bigger bags grow sturdier, larger seedlings but cost more media and space; smaller bags are cheaper and lighter but need planting out sooner. Enter your bag's volume so the media figures match what you'll actually use.
How do I convert litres of media to cubic metres?+
There are 1000 litres in a cubic metre, so total cubic metres = total litres ÷ 1000. Media is often sold or transported by the cubic metre or by the truckload, so the calculator gives both litres and m³ to make ordering and mixing straightforward.
What is this calculator for?+
It sizes a polybag nursery: from your target plants, mortality buffer and bag size it tells you how many bags to fill and how much potting media to prepare. That lets you order bags, mix the right volume of media and budget the nursery before you start filling, whether it's a forest, plantation or vegetable nursery.
Are the figures exact?+
They're solid planning estimates. Real bag and media needs vary with germination, actual mortality, how full you pack each bag and settling of the media. Add a little extra media for spillage and topping up, and refine the buffer against your own nursery records each season.