Gadenin日本語Get the appChoose the aspect before you choose the hole
The spring flush of red new growth is the reason for growing this shrub, and it is thin, soft tissue with no wax on it yet. Two things ruin it. A late frost blackens it outright. Cold drying wind pulls moisture out faster than the young roots can replace it and burns the leaf edges brown. Both are problems of position, and neither can be fixed by feeding or watering afterwards.
So look for a spot with something solid on the windward side, a wall, a fence, a hedge or a bigger evergreen, and with light shade overhead for part of the day. Avoid an open east-facing aspect above all others. Frosted young leaves thawing slowly in shade very often come through unmarked; the same leaves struck by low sun at dawn thaw so fast that the cells burst, and by mid-morning the flush is black.
Bright filtered light gives the best of both worlds: strong flower bud set, deep color in the flush and no bleaching of the mature leaves. Deep shade gives a sparse plant that barely flowers. Full hot sun bleaches the foliage to a tired yellow-green and creates the dry warm microclimate that lace bug thrives in.
Give it room. A pieris is slow but it does not stay small, and most reach five to eight feet (1.5 to 2.5 m) in both directions in time. Planting it tight against a path guarantees pruning it later, and this is a shrub that punishes badly timed pruning by not flowering.
| Position | Effect on the plant | Verdict |
|---|---|---|
| Sheltered, dappled shade, west or north aspect | Clean flush, good bud set, deep leaf color | Ideal |
| Open east-facing, catches early sun | Flush blackens after frost, repeatedly | Avoid |
| Exposed to prevailing wind | Brown scorched leaf edges each spring | Avoid or screen first |
| Full hot afternoon sun, dry soil | Bleached foliage, lace bug takes hold | Poor |
| Deep shade under dense trees | Thin growth, few flower buds | Poor |
| Foot of a rendered wall or new concrete | Lime leaches in, leaves go chlorotic | Avoid |
Get the soil acid before the plant goes in
Pieris will not thrive above about pH 6.0, and the safe target is 4.5 to 5.5. Test the ground where you intend to plant, taking the sample from four inches (10 cm) down. If the reading comes back near neutral or higher, deal with it now rather than after the shrub is in, because you cannot dig sulfur into a root zone once those shallow roots have spread.
Elemental sulfur worked into the top few inches is the slow, reliable way to bring the pH down, but it depends on soil bacteria to convert it, so it takes months and does very little in cold ground. Apply it while the soil is warm and allow a full growing season before you plant. Do not try to correct chalk or limestone soil. The parent rock keeps buffering the pH back up and you will be fighting it for the life of the plant.
On alkaline ground, grow the shrub in a large container of acidic potting mix instead. A pot of at least sixteen inches (40 cm) across, watered with rainwater, gives a better plant than a struggling specimen in a border you have tried to acidify. A raised bed filled with ericaceous mix works too, as long as it is deep enough that the roots never reach the native soil beneath.
Work plenty of composted bark, leaf mold or acidic potting mix into the whole planting area, not just the hole. The aim is an even, open, moisture-holding root run out to a radius of two or three feet (60 to 90 cm), because that is where the roots are actually going.
Plant shallow, and never deep
The commonest way to kill a pieris slowly is to bury it. The root system is fibrous and shallow and needs air in the top few inches. Set it an inch or two too low, or pile mulch against the stems, and the plant sulks for a couple of seasons with dull olive leaves and no new growth before it goes backwards altogether.
So the top of the rootball finishes level with the surrounding soil or half an inch (1 cm) proud of it, never below. Dig the hole wide rather than deep, at least twice the width of the rootball, and leave the base of the hole firm so the plant cannot sink as the soil settles.
Container-grown plants often arrive with a tight mat of roots circling the pot. Tease the outer roots loose with your fingers before planting, or they carry on circling and the shrub never anchors. If the rootball is dry, stand it in a bucket of water until the bubbles stop; a dry peaty rootball planted into damp soil stays dry, because water runs around it rather than into it.
- Soak the rootball first Stand the pot in water until air stops bubbling out, usually ten to twenty minutes. A dry rootball is very hard to rewet once it is surrounded by soil.
- Dig wide, not deep Twice the width of the rootball and exactly its depth. Leave the bottom of the hole undug and firm so the plant cannot settle lower than you set it.
- Loosen the outer roots Rub the sides of the rootball with your fingers to free the circling roots and pull a few outward. Do not shred the whole rootball apart; you only need the outside opened up.
- Set the level and check it with a cane Lay a cane across the hole. The top of the rootball should touch it or sit a fraction above. Backfill with the improved soil, firming gently in layers rather than stamping.
- Water in thoroughly Two or three gallons (8 to 12 liters) poured slowly, to settle the soil around the roots and drive out air pockets. Top up any hollow that appears, with soil rather than by treading.
- Mulch, keeping it off the stems Two to three inches (5 to 8 cm) of pine bark or pine needles over the whole area, pulled back an inch (2.5 cm) from the trunk so the bark at the base stays dry.
The first two years
A newly planted pieris has a rootball the size of its pot and nothing beyond it. Until the roots reach out into the surrounding soil, which takes a good two growing seasons, the plant depends entirely on you for water. Check it weekly through the first two summers and soak it whenever the top two inches (5 cm) are dry. Do not assume rain has done the job; a shrub under a wall or overhanging branches can stay bone dry through a wet week.
Hold off feeding until the second spring. There is enough in a decent planting mix for the first year, and pushing soft growth on an unestablished plant simply gives the frost something to kill. From the second spring, a single application of slow-release ericaceous fertilizer as growth starts is all it needs.
Do not prune anything in the first two years beyond removing damage. Let the plant build its framework. And record the planting date, the position and the pH reading you took, because in five years when a leaf problem shows up, those three facts are what tell you whether it is the site or the season.
If the shrub flowers heavily in its first spring after planting, pick the flower trusses off once they fade. Letting a newly planted pieris set seed diverts energy that it needs for roots, and the plant establishes noticeably faster without it.