How do I repot a shrub or tree that is too big to lift out of its pot?

Getting a root-bound shrub, olive or bay out of a container without breaking either — the knife cut, the tip-and-roll, the two-person slide, and when to break the pot instead.

Difficulty: intermediate
Time: 1 hr
Read: 4 min
Safety: caution

Short answer

Water it the day before, run a long knife or a pruning saw right round the inside of the pot to sever the circling roots, lay the pot on its side, and have one person pull the plant by the base of the trunk while another holds the pot back with a foot. If it will not move, cut the pot off.

Plants that have been in the same container for years anchor themselves in two ways: roots grow into every irregularity in the pot wall, and roots escape through the drainage holes and swell. Neither is solved by pulling harder. Both are solved by cutting.

Safety

A large planted pot easily exceeds a safe single-person lift, and pots break under strain and cut hands. Do not tip a heavy pot towards yourself, do not lever against glass or glazed ceramic, and get a second person for anything above about 40cm across. If the pot has to be sacrificed, breaking it deliberately is safer than fighting it.

What you'll need

A long bread knife, old carving knife or pruning saw, true
A second person for anything large, true
A tarpaulin or old sheet
Fresh loam-based compost
Secateurs or loppers

Step by step

Water thoroughly the day before.A moist rootball holds together and slides; a dry one crumbles and tears the fine roots off. Water until it runs out of the base, then leave it a full day to drain so it is not at maximum weight.
Choose the timing.Late autumn to early spring for deciduous plants, while they are dormant. Early to mid spring for evergreens, once the worst cold has passed but before growth is away. Never in summer on a plant in full leaf and full sun.
Cut the escaped roots at the drainage holes first.Turn the pot enough to see the base, or reach under it, and cut through anything that has grown out and thickened. This alone is often the only thing holding the pot on.
Run a blade right round the inside of the pot.Push a long knife or a pruning saw down between the rootball and the pot wall, hard against the wall, and work it all the way round. You are severing the felted root mat that has bonded to the pot. Go right to the base.
Lay the pot on its side on a tarpaulin.Never lift a big pot to pull a plant out of it upright. On its side, gravity is helping, the plant cannot fall, and one person can hold the pot while the other pulls.
Pull by the base of the trunk, and roll the pot.One person grips the main stem low down and pulls steadily along the axis of the pot. The other braces the pot with a foot and rocks or rotates it. Never pull on branches or on the head of the plant.
If it still will not come, sacrifice the pot.Cut a plastic pot down two sides with a sharp knife or tin snips. Break a terracotta pot deliberately with one firm blow of a hammer near the base, wearing goggles, with the pot on its side and a sheet over it. This is safer and quicker than continued force.
Deal with the roots before it goes back.Tease the outer mat loose all round, cut off anything circling, and shorten the thick woody roots. If you are going into a bigger pot this is enough; if it is going back into the same pot, root prune properly.
Repot at the same depth, into fresh compost.Loam-based compost, firmed in stages so there are no voids at the sides, with the top of the rootball at the same level as before and the watering gap left below the rim. Water thoroughly and keep out of wind and strong sun for a fortnight.

Tips

Buy the next pot before you start. A plant sitting bare-rooted on a tarpaulin in the wind for an hour is a plant losing fine roots by the minute.
Tapered pots release far more easily than straight-sided or bellied ones. If a pot narrows at the neck, assume from the start that it is coming off in pieces.
A sacrificial plastic liner pot inside a decorative container makes all of this a five-minute job next time.

Common mistakes

Levering with a spade against the pot rim — The rim is the weakest part and it snaps. If you must lever, lever against the rootball with a piece of timber protecting the rim.
Pulling on the branches — You tear the head off the rootball, damage the bark and often snap the main stem. All the pulling force goes through the trunk at its base.
Skipping the knife cut and pulling harder — The felted root mat is genuinely bonded to the pot. Force tears the entire outer root layer off the ball, which is the layer doing most of the work.

Questions people ask

How often does a large container shrub need repotting?

Every three to five years for most, and up to ten for slow-growing plants in a large loam-based pot. Signs are water running straight through, roots at the surface and out of the base, and a plant that wilts daily no matter how much you water.

Can I avoid this entirely?

Largely, by top-dressing annually and root pruning back into the same pot every few years instead of always going bigger. That is how mature specimens are kept in containers indefinitely.