Why a Stone Trough Beats a Border

Alpines were made for containers. In the wild they cling to scree, cliff ledges and gravel pockets where drainage is instant and competition is thin. A stone trough mimics that life almost perfectly, and it does it in a space no bigger than a doorstep. For anyone gardening on a balcony, a courtyard, a narrow passage beside the house or a patio that never quite got finished, a trough is the most rewarding square metre you can own.

The other advantage is control. You decide the soil, so you decide the drainage. You can raise the trough onto feet and lift the crown of a cushion plant clear of winter wet. You can turn it so the smallest treasures face the kitchen window. And because alpines are naturally compact, a single trough can hold a dozen different plants, each flowering in its own fortnight, so the display keeps renewing itself from March right through to October.

Choosing the Right Trough

Old stone troughs are lovely, but a well-made cast stone or reconstituted stone pan does the job and weighs a good deal less. Look for something at least 30cm across and 15cm deep. Shallower than that and the compost dries out too fast in July; much deeper and you are carrying weight you do not need.

Drainage holes matter more than the material. You want several, not one, and you want them clear. Before filling:

• Stand the trough on two bricks or purpose-made feet so water never pools underneath.
• Cover the holes with a piece of broken slate or a plastic mesh, not a solid crock that blocks flow.
• Add a 2–3cm layer of coarse grit or small gravel across the base.

Aim for a position in full sun. Alpines will tolerate a little shade, but they flower poorly in it and stretch into loose, floppy cushions. Shelter from the worst of the winter rain is a bonus; against a south-facing wall is ideal.

The Compost Mix That Keeps Them Alive

Most alpine failures are compost failures. Ordinary multipurpose is too rich and holds too much water, which rots the crowns of cushion plants during a wet British winter. You want something lean, open and gritty.

A reliable mix by volume is two parts loam-based compost, two parts horticultural grit, and one part coarse sand or fine chippings. If you are using peat-free compost, add an extra handful of grit, as these blends can hold moisture longer. Mix it in a bucket until it looks more like gravel than soil, then firm it only lightly.

Top the whole surface with a 1cm dressing of grit or small chippings once planted. This is not decoration. It keeps the collar of the plant dry, deters slugs, stops compost splashing onto leaves in rain, and suppresses weeds and liverwort.

Planting for Cushions, Creepers and Spring Bulbs

The trick to a trough that looks good for months rather than weeks is to combine three plant habits. Cushion and dome formers give structure and a long season of foliage. Creepers and trailers soften the edges and spill over the rim. Small bulbs thread through the gaps and give you the early colour that carries the display before the alpines get going.

Space plants so their mature spread just touches, and resist the temptation to overcrowd. A 40cm trough will comfortably take five or six alpines plus a scatter of bulbs. Plant in autumn or early spring, when the soil is moist and roots establish quickly.

• Cushions: saxifrage, dianthus, silene, androsace and the smaller campanulas.
• Creepers: aubrieta, arabis, thyme, phlox subulata and raoulia.
• Bulbs: dwarf iris, species tulips, grape hyacinth, squill and small narcissi.
• Late colour: sempervivum, sedum, lewisia and tiny gentians.

Watering, Feeding and Winter Care

Once established, a trough of alpines is genuinely low maintenance, but it is not no maintenance. Water thoroughly during dry spells in spring and summer, letting the water run out of the drainage holes, then leave it alone. Little and often is the wrong approach; alpines want a soak and a drying-out.

Feed sparingly. A single light dressing of a general-purpose fertiliser in early spring is enough. Overfeeding produces soft, sappy growth that flowers badly and collapses in the cold.

Winter is where most troughs are lost. Waterlogging, not frost, is the killer. Raise the trough onto feet, keep the grit top dressing topped up, and clear fallen leaves from the surface. In a very wet winter, a sheet of clear plastic propped over the trough on a frame will keep the worst of the rain off without shutting out light. Remove any dead rosettes and tired foliage in early spring, and trim back the creepers after flowering to keep the cushion plants from being swamped.

Watch for vine weevil in containers, and for aphids on soft new growth. Both are easier to deal with early, by hand where you can, than once a whole cushion has gone.

Getting Colour From March to October

If you plant with succession in mind, the trough will not have a dull fortnight. Start the year with dwarf iris and species tulips pushing through the grit in March and April. Follow with aubrieta and arabis spilling over the rim, then the saxifrages in April and May, when a well-grown cushion looks like a jewelled pincushion. Early summer brings dianthus and phlox, with their scent carrying across a warm patio.

Mid-summer belongs to the sempervivums and sedums, whose rosettes and foliage colours hold the trough together when flowers are scarce. Then the campanulas and small penstemons take you into late summer, with lewisia and gentians finishing the year in September and October. Add a couple of dwarf ornamental grasses or a small silver-leaved plant for texture, and the trough will still look composed in the depths of winter.

One trough is rarely enough. Start with one, learn how it dries out, how it fills, and which plants love it, then build a second. That is how most alpine collections begin, and it is a very pleasant way to spend a few square feet.