Tree bags range from 25 to 150 litres, and the right size depends on your tree's root ball and how long it stays in the bag.

Pick a bag that's too small and roots circle within months. Too large and you waste soil mix, water drains unevenly, and the tree sits in moisture it can't use. Most planting failures come down to getting this one decision wrong.

This guide covers how to match tree bag sizes to your project, when to step up in size, and the setup details that separate healthy root systems from root-bound disasters. Plus the common mistakes landscapers and nursery growers keep making.

What Are Tree Bags and Why Use Them?

Tree bags (also called planter bags or grow bags) are heavy-duty polyethylene or woven polypropylene containers used to grow trees in nurseries, on construction sites, and in residential landscapes. They replace rigid pots for anything from native seedlings to advanced specimens.

The main advantage is air pruning. When roots hit the porous bag wall, they stop extending and branch sideways instead. This prevents the spiralling root structure you get in hard-walled pots, which can strangle a tree years after planting.

• Air pruning promotes a denser, fibrous root system
• Lighter than equivalent plastic pots, so easier to move on site
• Flat-pack storage saves warehouse space between projects
• UV-stabilised options last 3+ years in direct Australian sun
• Available from 25L up to 150L+ for advanced specimens

Nurseries across Australia have largely switched from rigid containers to planter bags for trees above 25 litres. The weight saving alone is significant when you're moving 200 trees onto a landscaping job.

How to Pick the Right Tree Bag Size

The rule of thumb: your tree bag should be roughly double the volume of the existing root ball. A tree in a 15L nursery pot goes into a 35 Litre Planter Bag. One in a 25L pot steps up to a 45 Litre or 75 Litre bag.

All Stake Supply stocks round planter bags in all six sizes, from the 25 Litre through to the 150 Litre. The UV-stabilised material handles full Australian sun without breaking down.

Tree Bags vs Pots for Growing Trees

Hard-walled pots still have their place for retail display and small ornamentals. But once you're growing trees beyond 25 litres, planter bags win on almost every measure.

• Root health: Bags encourage air pruning. Pots cause root circling.
• Weight: A 100L planter bag weighs a fraction of a rigid pot the same size.
• Storage: Bags fold flat. Pots stack but still take up floor space.
• Drainage: Bags drain freely through the fabric. Pots rely on drainage holes that clog with soil.
• Cost: Bags cost less per unit, especially in bulk orders.

The one area where pots win is presentation. If a tree sits in a garden centre waiting for a customer, a rigid pot looks more polished. But on a construction site or in a holding nursery, nobody cares about aesthetics. They care about root quality and whether the tree survives transplanting.

How to Set Up Tree Bags on Site

Getting the growing medium right matters more than the bag itself. Tree bags drain faster than pots, so your soil mix needs to hold moisture without staying waterlogged.

1. Fill the bottom third of the bag with your growing medium and tamp lightly.
2. Place the root ball in the centre, making sure the top sits 20 to 30mm below the bag rim.
3. Backfill around the root ball, pressing firmly to eliminate air pockets.
4. Water thoroughly until it runs out the base.
5. Mulch the top 20 to 30mm with coarse bark or gravel to reduce evaporation.
6. Place bags on a free-draining surface. Sitting on bare soil invites roots to escape through the base.

For growing medium additives, TerraCottem Arbor Soil Conditioner improves water retention in planter bags without creating waterlogging. Mix it through the backfill at the manufacturer's recommended rate.

Tree Bag Mistakes That Kill Plants

Most tree bag failures aren't about the bag. They're about how people use them.

• Wrong growing medium. Standard garden soil compacts in bags and suffocates roots. Use a free-draining nursery mix with bark, perlite, or coarse sand.
• No drainage underneath. Bags on concrete or compacted clay pool water at the base. Stand them on gravel or mesh.
• Skipping fertiliser. Tree bags leach nutrients faster than garden beds. Use a controlled-release fertiliser like Troforte Professional Landscape Trees & Shrubs at planting.
• Ignoring wind. Large bags with tall trees become sails. Stake the tree and consider hessian panels as windbreaks for exposed nursery rows.
• Watering on a pot schedule. Bags dry out faster than pots because air moves through the walls. Increase watering frequency by 20 to 30% compared to a rigid container.

The single biggest mistake is leaving trees in bags too long without potting up. A tree that's been root-bound for six months doesn't transplant well, regardless of how good the bag is.

When to Transplant Out of a Tree Bag

A tree is ready to come out of its bag when roots are visible at the outer wall but haven't started circling. You want fibrous white tips touching the fabric, not a dense mat wrapping the inside surface.

• Roots visible through the bag walls on multiple sides
• Water runs straight through without the soil absorbing it
• The tree dries out within 24 hours of a deep watering
• Growth has slowed despite adequate fertiliser and sunlight

For landscaping jobs, the ideal is to transplant directly from bag to ground. The root system in a well-managed tree bag establishes faster than one from a rigid pot because there's no circling to undo. The Australian Department of Climate Change, Energy, the Environment and Water recommends planting native trees with intact root systems for best survival rates in revegetation projects.

If the tree needs to stay containerised longer, step up to the next bag size. A tree in a 75 Litre Planter Bag showing root-bound signs goes into a 100 Litre or 150 Litre bag for another growing season.

Where to Buy Tree Bags in Australia

All Stake Supply has stocked planter bags from their St Marys warehouse in western Sydney since 1976. They carry 25 Litre, 35 Litre, 45 Litre, 75 Litre, 100 Litre, and 150 Litre round planter bags, all UV-stabilised for Australian conditions.

Beyond the bags themselves, they stock everything for a tree growing operation: tree guards for protection, hessian tree ties for staking, and weed mat for ground cover between bag rows.

• UV-stabilised material rated for 3+ years in Australian conditions
• Reinforced handles on bags 75L and above for easier transport
• Round base design that distributes root growth more evenly than square bags
• Free drainage built into the base fabric

According to NSW Department of Primary Industries, container-grown trees with air-pruned root systems have higher survival rates after transplanting than field-grown or pot-bound stock.

Browse the full product range at All Stake Supply or contact the team for trade pricing and bulk orders.