Why has my plant stopped growing?

A plant that is alive but static is nearly always short of root room, root health, light or warmth — checked in that order, cheapest first.

Difficulty: beginner
Time: 20 min
Read: 5 min

Short answer

Check the roots before anything else. A pot-bound or rotted root system stops growth completely while the plant still looks alive, and both are found in thirty seconds by sliding the pot off. If the roots are fine, count the hours of direct light and check the soil temperature. Feeding is the last thing on the list, not the first.

Stalling is different from dying. The plant holds its leaves, keeps its colour, and simply does not get any bigger for weeks in the middle of the growing season. That is nearly always a physical limit rather than a disease, and the limits are few enough to work through in an afternoon.

Step by step

Confirm that it should be growing at all.Nothing much grows below about 6°C, many plants pause in high summer heat and drought, and a great many take a deliberate rest — spring bulbs, Mediterranean shrubs in August, houseplants from October to February. A plant that has stopped in November is behaving correctly.
Slide the pot off and look.A dense mat of circling roots with no compost visible means the plant has run out of room and will not grow again until it is potted on or root-pruned. Brown, soft roots that slide out of their skins mean rot, and that is a different repair.
Check for a physical limit in the ground.A plant in a bed can hit a buried slab, builders' rubble, a compaction pan or a mass of tree roots. Push a fork or a metal rod into the soil at several points and see where it stops.
Count the hours of direct light.A plant in less light than it needs does not die, it just stops — smaller leaves, longer gaps between them, no new shoots. Watch it at three points in a day before deciding, because people consistently overestimate how sunny a spot is.
Look for root pests.Vine weevil grubs, root aphids and root mealybug all remove the plant's ability to grow while everything above ground still looks alive. Knock the plant out and look at the rootball and the inside of the pot.
Check the watering rhythm.A plant that dries out completely between waterings stops growing each time it does, and never really gets going. So does one in permanently saturated compost. Consistency matters more than quantity.
Check for soil temperature and cold roots.In spring, a plant with warm air and cold soil will hold still for weeks. Purple leaves are the giveaway. Fleece, a cloche, or simply waiting solves it.
Look for damage at the growing point.If the leading shoot has been eaten, frosted, snapped or pinched out, the plant has to build a new leader from a side bud, which takes time. On a young tree this shows as a season of very little apparent progress.
Only then consider feeding.Feeding matters most in containers, where nutrients leach out and fresh compost is exhausted after about six weeks. It matters least in a fertile bed. Never feed a plant that is dry, waterlogged, root-damaged or dormant — that is where feeding does harm.
Give it time and measure it.Put a cane beside the plant and mark the top of the growth with tape. In three weeks you will know whether the change you made worked, which memory alone will not tell you.

Tips

New shrubs and trees genuinely do very little above ground for a season or two while they build roots. This is normal and is not a fault.
A plant that has been moved does nothing for weeks while it re-roots. Do not respond by feeding or by moving it again.
Potting on into a much larger pot does not accelerate growth. The unused compost stays wet and the roots rot. One or two sizes at a time.
Growth in leaves, growth in roots and growth in flowers compete. A plant flowering heavily or carrying a big crop is not going to put on much size at the same time.

Common mistakes

Feeding first — Almost none of the common causes are nutritional, and fertiliser on damaged roots or dry compost causes scorch. It is the last check, not the first.
Watering more because it looks stalled — Waterlogged compost is one of the causes. Check the moisture before adding anything.
Assuming a plant that has stopped is dying — Static and alive is a completely different situation from declining. Judge by whether it is losing leaves and colour, not by whether it is getting bigger.

If it doesn't work

Dense circling roots, water runs straight through

Cause: Pot-bound — Fix: Cut the circling roots, pot on one or two sizes, or root-prune and return to the same pot with fresh compost.

Brown soft roots, sour smell, wilting in wet compost

Cause: Root rot — Fix: Wash the roots, cut back to firm tissue, reduce the top growth to match, repot into fresh compost, and do not feed for a month.

Small pale leaves, long gaps between them, leaning

Cause: Too little light — Fix: Move it, gradually if it is a houseplant, and cut back to a bud to force branching once it is in better light.

Purple leaves, cold spring, no growth at all

Cause: Soil too cold for root activity — Fix: Fleece or cloche, water with tepid water, and wait for the soil to warm rather than intervening.

Wilting in moist compost, plant lifts out with almost no roots

Cause: Vine weevil grubs or root aphid — Fix: Repot into fresh compost, wash the roots, apply nematodes, and treat every pot in the group.

Questions people ask

How long should a plant take to respond after I fix something?

Two to three weeks in the growing season before there is anything to see, and longer for a woody plant. Change one thing, mark the growth, and wait — changing several things tells you nothing.

Should I cut it back to stimulate growth?

On a plant with healthy roots, yes — pruning does prompt new shoots. On a plant whose roots are the problem it makes things worse, because it removes the leaves it needs to rebuild them.

Do plants stop growing when they flower?

Largely, yes. Flowering and fruiting take priority over extension growth, which is why deadheading and removing fruit on a young plant encourages it to get bigger.