Gadenin日本語Get the appChoosing the position
This is a small tree, typically reaching fifteen to thirty feet (4.5 to 9 m) with a spread close to its height, so give it room to become a wide, tiered shape rather than squeezing it against a boundary. Because the flower bracts sit on top of the horizontal branch layers, the display is seen best from slightly below or from the side, which makes a lawn edge, the turn of a path or a view from an upstairs window ideal placements.
Full sun to light shade both work. In cooler regions full sun gives the heaviest bract display and the best autumn color. In hot summer regions, aim for morning sun with shade through the hottest part of the afternoon, because the shallow roots and thin leaves make this tree an early sufferer in heat and drought.
Avoid three positions in particular: the reflected heat trap beside paving or a south-facing wall, the still airless corner where powdery mildew settles in, and any place where the root plate will later be paved, trenched or driven over. Also think about the fruit. The knobbly red berries drop in quantity in late summer and turn to mush underfoot, so keep the canopy from overhanging a path, a patio or a parking space unless you are happy to sweep.
| Site factor | What the tree wants | Why it matters |
|---|---|---|
| Light | Full sun in cool regions, afternoon shade where summers are hot | Bract count versus leaf scorch |
| Soil | Moisture-retentive but free-draining, slightly acid pH 5.5 to 6.5 | Yellowing between the veins on alkaline ground |
| Air movement | Open, not boxed in by walls or shrubs | Still air feeds powdery mildew |
| Space | 15 to 30 ft (4.5 to 9 m) each way | Wide tiered habit, resents corrective pruning |
| Under the canopy | Bed or mulch, not path or patio | Falling fruit is soft and stains |
| Root area | Never to be dug, paved or compacted | Feeding roots run just below the surface |
Digging the hole and setting the depth
Dig wide and shallow, which is the opposite of the instinct most people bring to tree planting. Make the hole two to three times the width of the rootball and no deeper than the rootball itself, with the sides broken up rather than smooth. A wide loosened area is what a shallow-rooting tree needs; a deep pit only settles later and pulls the trunk down with it.
Depth is the decision that comes back to haunt people. Set the tree so that the root flare, the point where the trunk widens out into the first roots, sits at or very slightly above the surrounding soil level. Container trees are frequently potted too deep at the nursery, so scrape the surface compost away until you can actually see the flare before you measure anything.
Planting too deep does not kill a dogwood quickly. It produces a tree that never quite grows away, then stalls and thins in the canopy three or four years later, long after anyone connects the two events. If in doubt on heavy or wet soil, plant an inch or two (3 to 5 cm) proud and mound soil gently up to the rootball edge.
- Find the flare first Before digging, scrape compost off the top of the rootball until the trunk visibly widens into roots. Measure the rootball depth from that point, not from the pot rim, and dig to match.
- Dig wide, not deep Open a hole two to three times the rootball width and exactly the rootball depth. Roughen the sides. Leave the base undug so the tree cannot sink as loose soil settles.
- Handle the roots gently Slide the rootball in whole. Tease out or cut through only roots that are genuinely circling the pot. Do not shake apart or wash off the rootball; the fine roots break rather than bend and are slow to replace.
- Backfill with what came out Use the excavated soil, improved with compost mixed through the whole loosened area rather than dumped in the hole. A rich pocket in poor ground encourages the roots to circle inside it instead of ranging out.
- Water in and settle Water thoroughly to collapse air pockets, then firm with the flat of your hands rather than treading. Top up with soil if the surface sinks, keeping the flare visible.
- Mulch and leave the collar clear Spread 2 to 3 in (5 to 8 cm) of coarse mulch over the whole loosened area and out beyond it, keeping a clear ring 3 to 4 in (8 to 10 cm) wide around the trunk.
The first two years decide the next twenty
A young kousa dogwood resents drought badly, and the establishment period is when almost all avoidable losses happen. Until the roots have spread well beyond the original rootball, which takes two to three growing seasons, the tree is drawing water from a volume of soil not much larger than the pot it arrived in. That volume can dry out in a few days of heat.
Water deeply once a week through dry weather in the first season, tapering to every ten to fourteen days in the second and third. Deliver the water slowly over the whole mulched area rather than in a rush at the trunk. Skip a week when the soil four inches (10 cm) down is still cool and damp.
Do not feed at planting and do not prune to shape. Both push the tree in the wrong direction at the wrong time: fertilizer buys soft top growth the young root system cannot support, and this species responds poorly to cuts at any age. Stake only if the site is genuinely windy, low and loose, and remove the stake after one to two years so the trunk can build its own strength.
Autumn and early spring both suit planting. Where winters are hard or the soil is cold and heavy, plant in spring so the tree gets a full growing season of root growth before its first winter.
Record the planting day
Write down the planting date, the exact position, the depth you set the flare at and the size of the tree when it went in. That last figure matters more than it seems, because slowing shoot extension is the earliest visible sign that something is wrong under the ground, and you cannot judge it without a starting point.
Add the first flowering season to the same note. A young kousa often takes a few years to settle into a full display, and having the planting date beside the first heavy bract year tells you what to expect if you ever plant another one in the same garden.