Gadenin日本語Get the appDecide indoors or outdoors before you plant
The plant is the same; the two jobs are not. Indoors you are containing a fast tree in a pot and managing it for a shape. Outdoors in a frost-free or nearly frost-free climate you are planting a vigorous shade tree that will outgrow a small garden and keep going. It handles brief cold to around 25F (-4C) once established, but young plants are cut back by anything at or below freezing.
If your winters drop below freezing at all, keep it in a pot you can carry and treat it as a plant that summers outside and winters in. That is also the arrangement that gives the best-looking indoor tree, because a summer outdoors builds the dense canopy that a room cannot.
| Situation | Approach | Key risk |
|---|---|---|
| Hard frost every winter | Pot only, indoors from first frost | Cold damage to young stems |
| Light or occasional frost | Sheltered spot outdoors, or a movable pot | Dieback in a bad year |
| Frost-free, mild | Open ground, sited well away from structures | Outgrows the space fast |
| Frost-free, subtropical | Check local advice before planting out | Self-seeds and escapes |
Potting: size up slowly, drain hard
Choose a pot two inches (5 cm) wider than the current one, no more. A tree sitting in a large volume of compost it cannot fill keeps that compost wet for weeks, and wet compost around fine ash roots is how most container plants are lost. Drainage holes are non-negotiable; a decorative pot with no hole is a cachepot, not a planter.
Use a free-draining mix: roughly two parts general-purpose potting mix to one part coarse perlite, bark or grit. The finished mix should feel gritty and fall apart in your hand rather than forming a ball. Do not put a layer of gravel in the bottom - it raises the wet zone rather than lowering it.
- Water the plant the day before A rootball that is already moist slides out of its pot in one piece. A bone-dry one crumbles and tears fine roots as it goes.
- Set the depth first Add compost until the top of the rootball will sit about half an inch (1 cm) below the pot rim. Burying the stem bases deeper than they were rots the bark.
- Fill and firm in stages Work compost down the sides with your fingers in two or three rounds, firming lightly each time. Big air pockets dry out and kill the roots that run through them.
- Water through, then leave it alone Water until it runs out of the base, then put it in bright light and do not water again until the top two inches (5 cm) are dry. Do not feed for six weeks.
Planting in open ground
Dig a hole twice as wide as the rootball and exactly as deep, so the plant sits at the depth it grew at. Loosen the sides of the hole if the soil is heavy, backfill with the soil you removed rather than rich compost, and firm with your heel. Water it in with several gallons, and keep watering deeply once a week through the first two dry seasons - that is what gets a young tree established.
Mulch a ring two to three inches (5 to 8 cm) deep out to the edge of the canopy, pulled back a hand's width from the trunk. Stake only if the site is windy, use a low tie about a third of the way up the stem, and remove the stake after a year so the trunk thickens properly.
Space it at least 20 feet (6 m) from a house, wall, drain run or paving. It is a fast tree with a spreading root system, and it will find a cracked drain.
Where not to plant it at all
In warm subtropical regions this species has escaped cultivation and is treated as a weedy invader, spreading by wind-borne seed into bushland and along watercourses and forming dense thickets that shade out native regeneration. Some jurisdictions restrict or discourage planting it for exactly that reason.
Check the local weed list before you put one in open ground in a mild or subtropical climate. If it is listed, grow it in a pot where you can pick the seed off, or choose something else. A tree that seeds itself into a neighboring reserve is not a problem you can prune away later.
What to record on planting day
Write down the date, the pot size or planting position, the compost mix you used and the height of the plant at the trunk. Height at planting compared with height a year on is the clearest measure of whether the site suits it, and it is the number people always wish they had.
For a potted tree, also note the pot's diameter and the date. Evergreen ash typically needs the next size up every second warm season while young, and having the last potting date saved means you are not guessing when the growth slows.