Gadenin日本語Get the appThis is a forest tree, not a bed crop
Koshiabura, a thornless relative of the angelica tree, grows naturally on the edges and clearings of deciduous woodland, where it gets broken light for most of the day and deep, leafy, free-draining soil underneath. Everything about how it behaves in a garden follows from that. It is slow, it resents both baking sun and heavy wet ground, and it will not be hurried by feeding or watering into cropping earlier than it means to.
The practical consequence is that you are planting a tree you will not pick from for several years. Depending on the size of the plant you start with and how well the site suits it, expect four to six years before a stem is thick enough and tall enough to give a terminal bud worth taking, and longer if the plant went in as a seedling. Plant it accordingly, in a position you are not going to want back.
Do not plant koshiabura into a vegetable bed or a spot you rotate. It resents root disturbance, it makes almost no growth in its first two seasons, and moving it later costs you the years you have already waited.
Reading the site before you dig
The single most common failure is planting it in full sun on the assumption that more light means faster growth. In open sun the leaves scorch at the margins by midsummer, the tree stalls, and the shoots that do come are short and tough. Broken light under high deciduous canopy, or a north or east aspect that gets a few hours of morning sun and shade through the afternoon, is what you are aiming for.
| Factor | What you want | Sign the site is wrong |
|---|---|---|
| Light | Dappled shade, or morning sun with afternoon shade | Scorched leaf margins by midsummer, stalled growth |
| Soil | Deep, leafy, free-draining loam with plenty of organic matter | Standing water after rain, gray or sour-smelling subsoil |
| pH | Slightly acid to neutral, roughly 5.5 to 6.8 | Yellowing between the leaf veins on chalky ground |
| Shelter | Out of drying wind, backed by a hedge, wall or tree line | Torn leaflets, one-sided crown, wind-rocked stem |
| Depth of soil | At least eighteen inches (45 cm) of workable soil | Roots hitting rock or hardpan within a spade's depth |
| Root competition | Away from the drip line of dense surface-rooted trees | Bone-dry soil under the canopy all summer |
Getting the tree in the ground
Plant during dormancy, from leaf fall through to the point in late winter when the buds begin to swell. Bare-root stock goes in at the dormant end of that window; container plants can go in later, but avoid planting once growth has started, because a tree pushing leaves has no spare capacity to make roots.
- Dig wide, not deep Open a hole two to three times the width of the root ball but only as deep as the roots themselves. The feeding roots run near the surface, so loosening a wide area matters far more than digging down.
- Fork the sides and base On clay especially, break the glazed faces of the hole with a fork so roots can move out into the surrounding soil rather than circling in a sump.
- Set the collar at soil level The point where the roots flare from the stem sits level with the surrounding ground, never below it. A buried collar on this species leads to rot at the base within a few seasons.
- Backfill with the soil you dug out Mix in a couple of handfuls of leaf mold or well-rotted compost, but do not build a rich pocket in poor ground. Firm gently with your heel as you go and water in thoroughly to settle the soil around the roots.
- Mulch, keeping the stem clear Lay two to three inches (5 to 8 cm) of leaf mold or bark over the root zone, out to a couple of feet (60 cm), with a clear ring of two inches (5 cm) around the stem itself.
- Stake only if the site is windy Use a low stake tied at about a third of the stem's height, so the top can still flex. Remove it after two growing seasons; a permanently rigid stem never thickens properly.
Spacing and how many to plant
A mature koshiabura is a small to medium tree, and in the open it will reach twenty to thirty feet (6 to 9 m) in time, though under garden shade and regular picking it usually stays well short of that. Plant single specimens at least ten feet (3 m) from anything they will have to compete with, and space trees within a small grove twelve to fifteen feet (3.5 to 4.5 m) apart.
Plant more than one if you can. This matters less for pollination than for harvest discipline: with a single tree there is exactly one terminal bud worth taking each spring, and the temptation to take a second is hard to resist. Three or four trees give you a harvest that is worth having while still leaving each individual tree cut only once.
Set up your records on planting day
Write down the planting date, the size and form of the plant that went in, and where exactly it stands, ideally as a sketch with two measured distances from fixed points. Slow trees vanish into the background, and a dormant koshiabura under a hedge is very easy to strim off by accident in its second spring.
Then start a one-line note each year at leaf fall: the height of the leading stem, the number of stems thick enough to consider picking from, and whether the site was ever waterlogged or scorched that season. Those notes are what tell you, several years from now, that the tree is finally ready to be picked, rather than you guessing and cutting a stem that was not.