Field maple

A year of care. RHS H6: a native tree, hardy in the ground; a shallow pot still wants shelter from a hard frost, because frozen roots cannot replace what a drying wind takes from the twigs. USDA 6b/7a, the RHS's own equivalent.

Timings for a temperate northern climate.

• Repot
• Wire
• Prune
• Pinch
• Protect
• Feed
• Water
• Watch for pests

1. J
2. F
3. M
4. A
5. M
6. J
7. J
8. A
9. S
10. O
11. N
12. D

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• JanuaryDormant and content outside. Shelter the pot from the worst frost and from drying wind by putting it on the ground, against a wall or under a bench; a cold frame is a luxury this species does not need, though it does no harm. Check the soil is damp weekly. Bare-root hedging whips for a forest planting are sold now and can be heeled into a box of soil until March.protect, water
• FebruaryStructural work on a bare tree: the trunk chop on a collected stump, removal of a heavy branch, shortening a long leader. Seal the cuts. Collected hedgerow trees are lifted this month or next, with as much root as the hedge allows, and potted in a free- draining mix in a deep box. The buds move at the end of the month in a mild year.prune
• MarchRepot as the buds swell, every two years for a young tree and every three or four for an old one. Comb the roots out and remove up to a third. A forest of whips is assembled now: root-pruned hard, set in a shallow tray with the tallest tree a little forward of centre, tied in, and left to grow. Keep repotted trees out of wind and frost for three weeks.repot, protect
• AprilLeaves open. A late frost can blacken the new growth, and although a field maple recovers, fleece on a clear, still night saves the season. Pinch the opening shoots on a tree in refinement to the first pair of leaves; let a collected tree or a forest in its first year grow freely. Water daily when the surface dries.pinch, protect, water
• MayGrowth is fast and the pot dries daily; water every day and twice in a warm spell. Begin feeding when the leaves harden: a balanced feed weekly for a tree being developed, fortnightly at half strength for one in refinement. Keep pinching. Squash the aphids on the shoot tips before they curl the leaves.water, feed, pinch, pests
• JuneCut the spring extension back to one or two pairs of leaves on shoots you want to ramify; a strong, established tree can be partly or fully defoliated in early June for a smaller second set of leaves. A collected tree in its first year is left alone to build root. Wire young shoots now if you must, checking it every two weeks; the tree is more forgiving of wire than other maples but still thickens fast.prune, pinch, wire, water
• JulyWater is the job. Full sun is fine for this species and keeps the leaves small, but a pot in full sun dries by lunchtime, so water morning and evening. Feed lightly. Watch for powdery mildew in a hot, still spell and move the tree somewhere airier if it appears. Tidy long shoots.water, feed, pests
• AugustAs July, with any second flush pinched as it comes. Late in the month a nematode drench for vine weevil while the soil is warm. Check wire and remove any that is marking; a branch set in June will usually hold by now.water, feed, pests, wire
• SeptemberGrowth stops. Give two low-nitrogen feeds to harden the wood and then stop. Water less as the nights cool. A good month to look at a developing tree and decide which branches to keep for next year; mark them, but make the cuts in winter.feed, water
• OctoberYellow autumn colour in the second half of the month. Stop feeding. After leaf drop, wire young shoots if needed; the bark tolerates it over winter and the wire comes off in spring. Clear fallen leaves from the soil. Bare-root hedging whips go on sale in a few weeks if you are planning a forest.wire, prune
• NovemberDormant. Water only if the soil is drying, which in November it seldom is; make sure the pot drains, on feet and tilted a little if the rain is relentless. The pot can stay out in all but a hard, windy frost. Remove any wire that is biting.water, protect, wire
• DecemberLeave it cold, damp and sheltered. Check the soil after frosts for ice-heave and drainage. Light tidying of crossing twigs is fine on a bare tree; the big cuts wait for February. Hedge-laying season is a good time to ask a farmer or a hedge-layer for the stumps and trunks they are taking out, which is where the best field maple material comes from.protect, water, prune

Soil for this species: 2 parts akadama, 1 part pumice, 1 part lava (by volume); it also does well in a cheaper mix of 1 part akadama to 1 part horticultural grit for a tree in training. Tools and materials: starter kits.