Gadenin日本語Get the appThe aspect decision comes before everything else
Most magnolia disappointment traces back to one thing, and it is not soil, feeding or pruning. It is where the tree faces. The flowers of the early-blooming kinds open while frost is still possible, and a flower that froze overnight turns brown, limp and translucent within a day. Whether that happens is decided less by how cold the night was than by how fast the flowers thaw in the morning.
This is why an east-facing position is the wrong one. East light hits the tree first thing, thawing frozen petals in minutes rather than over an hour, and the cell walls rupture as they warm. The same night on the same tree in a west-facing or north-facing spot often does no visible damage at all, because the flowers come up to air temperature slowly in shade before the sun reaches them.
Wind exposure does the same job by a different route. An open, exposed site gives you no still air around the canopy on a radiation-frost night, and it also shreds the large petals mechanically. A magnolia in a windy garden loses flowers to tearing even in a mild season. Shelter is not a luxury for this plant; it is the difference between a display and a mess.
| Site | What happens to the open flowers | Verdict |
|---|---|---|
| East-facing, open | Frozen petals thaw fast in early sun and go brown | Avoid |
| Exposed on all sides | Petals tear in wind, no still air on frost nights | Avoid |
| Frost pocket at the bottom of a slope | Cold air pools and sits under the canopy | Avoid |
| West-facing with shelter behind | Slow thaw, flowers usually come through | Good |
| North side of a wall or hedge | Latest flowering, least frost damage | Good |
| Sheltered by evergreens to windward | Still air, flowers hold their shape | Good |
Light, and how much you actually need
Magnolias flower well on four to six hours of direct sun, which is less than most flowering trees need. That headroom is what lets you trade morning sun away for safety. Give the tree its light in the afternoon rather than at dawn and you lose almost nothing in flower count while removing the main cause of flower loss.
Deep shade is a different matter. Under a closed canopy the tree stretches, the branches thin out and flowering drops off sharply. Aim for open sky above the tree and shelter at ground and canopy level from the windward side. A high hedge or a group of evergreens twenty to thirty feet (6 to 9 m) upwind is close to ideal; a solid wall immediately behind the tree is not, because it radiates stored heat and can wake the buds too early.
Soil, and how deep to dig
Magnolias want moisture-retentive, free-draining soil with plenty of organic matter, and they are happiest slightly acid, roughly pH 5.5 to 6.5. They will grow on neutral ground. Thin chalky soil is the one situation where you are genuinely fighting the plant, and there the leaves yellow between the veins no matter what you feed.
Dig a wide, shallow hole rather than a deep one. Two to three times the width of the rootball and no deeper than the rootball itself is right. The roots of a magnolia are fleshy, shallow and brittle, and they run outward near the surface rather than down. A wide loosened area is exactly what they want; a deep pit only settles and drops the trunk too low.
Set the tree at the depth it grew in the pot, or a fraction proud of the surrounding soil on heavy ground. Planting a magnolia too deep is a slow killer that shows up two or three years later as stalled growth and dieback, long after you have forgotten the planting day. Firm gently with the flat of your hands, not by treading, because heavy compaction snaps the surface roots you cannot see.
Autumn or early spring planting both work, but on cold or heavy soils plant in spring so the roots have a full warm season before their first winter.
Handling the rootball and the first two seasons
Those fleshy roots break rather than bend, and they heal slowly when broken. Do not tease out or tickle the rootball the way you would with a shrub, and do not cut into it unless it is genuinely circling. Slide the plant into the hole in one piece and backfill with the soil you took out, improved with a couple of buckets of compost mixed through the whole loosened area.
Water in thoroughly at planting, then keep the tree watered through its first two growing seasons whenever there is a dry spell of more than a week or ten days. A magnolia that dries out badly in its establishment years drops leaves in midsummer and sets almost no flower buds for the following spring, so the setback shows up a year later.
Mulch two to three inches (5 to 8 cm) deep over a circle at least three feet (1 m) across, kept an inch or two clear of the trunk. On a magnolia the mulch is not cosmetic. It is what protects the shallow root plate from drying, from summer heat and from the fork of a well-meaning gardener.
Write down what you planted and where
Record the planting date, the exact position relative to a fixed landmark, the aspect it faces and which direction the shelter comes from. In four or five years, when you are deciding whether a poor flowering season was frost, drought or shade, the only way to answer it is against notes from the years when things went right.
It is also worth recording the spread of the mulch circle and the date you stopped watering. Establishment failures on magnolia are almost always traced back to a dry summer in year one or two, and nobody remembers that accurately without having written it down at the time.