Why Layering Beats Starting Again

A border that only performs in September is a border doing half a job. The trick reliable gardeners use is not to choose between spring bulbs and autumn perennials, but to plant one beneath the other. Bulbs do their work early, before the asters and sedums have woken up properly; by the time the bulb foliage is yellowing and spent, the perennials are rising and hiding the evidence. You get two seasons of interest from a single patch of ground, and far less bare earth to stare at in February.

The method is simple. It is the timing and the spacing that catch people out.

Getting the Bulbs Right

Not every bulb suits life under a herbaceous perennial. You want things that flower early, finish cleanly and tolerate a certain amount of root competition in summer, when the asters and sedums are drinking everything in sight.

• Snowdrops and winter aconites for the earliest possible show, planted in tight clumps at around 8cm deep. Buy them "in the green" in late winter if you can — dried snowdrop bulbs are notoriously sulky.
• Crocus and Iris reticulata at 8–10cm. Both are small enough to slot between the crowns of perennials without disturbing anything.
• Narcissi, particularly shorter cultivars at 10–15cm. They shrug off summer drought under a canopy of foliage far better than tulips do.
• Tulips at 15–20cm, but treat them as annuals in heavy soil. They resent the damp that comes with a well-watered border.

Avoid anything tall and top-heavy. A 60cm allium pushing up through a sedum clump is charming in June; a leggy Darwin tulip flopping across your asters in May is not.

Planting Beneath Existing Perennials

The practical difficulty is that the space you want to plant into is already occupied. Sedums in particular sit tight to the ground, with a woody crown and a ring of fleshy stems that leaves little room.

Work around the outer edge of each clump rather than directly beneath the crown. That ring of soil is where the roots of your perennials are least congested and where bulb foliage gets the light it needs in March. Use a long-handled bulb planter, or a trowel if the ground is loose, and lever the soil out carefully — you will feel the difference immediately between a bulb-sized pocket of soil and a thick fleshy root.

If a perennial is due to be divided anyway, do it in early autumn, plant your bulbs in the gap, and replant smaller divisions around them. You gain a season of vigour in the perennial and a clear run for the bulbs. Space bulbs roughly two to three times their own depth apart, and add a handful of grit to the base of each hole if your soil holds water.

Mark what you have planted. A few short cane offcuts or discreet labels will save you slicing through a drift of crocus with a spade in April.

Pairing With Asters and Sedums

Asters and sedums are the ideal partners because they emerge late and grow fast. A Symphyotrichum like 'Little Carlow' stays low until May, then rockets away, so the daffodils beneath it have a clear six weeks to fatten up. The sedums — Hylotelephium 'Matrona', 'Herbstfreude' and the darker 'Purple Emperor' — are even better, since they emerge as tight grey-green buds in April and only begin to sprawl in June.

Underplant the asters with white and pale blue bulbs. Crocus 'Jeanne d'Arc' and Narcissus 'Thalia' pick up the cooler end of the aster palette beautifully, and white reads clearly against dark emerging foliage. Beneath sedums, use warmer tones — apricot crocus or small species tulips — because the sedum flowers themselves run from pink through to deep burgundy.

Using Copper-Toned Foliage as the Bridge

The awkward fortnight is late May, when the bulbs have gone over and the perennials are still filling out. This is where copper and bronze foliage earns its keep.

• Heuchera cultivars in caramel and amber hold colour all winter and sit low enough to be planted in the same ring as your bulbs.
• Bronze fennel emerges early and its feathery copper fronds knit the gap between fading bulb leaves and new perennial growth.
• Carex buchananii and other bronze sedges give a year-round anchor at the front of the border.
• Physocarpus 'Diabolo', for a larger border, provides dark copper height while everything else catches up.

Copper also flatters the pink and purple of late asters in a way that plain green never does, and it stops the border reading as a single wash of autumn colour.

Seasonal Care Through the Year

Autumn. Plant bulbs from October to early December. Leave aster stems standing — the seedheads feed goldfinches and the hollow stems shelter overwintering insects. Cut them back to the ground in early March, not November.

Late winter. If you have mulched heavily, fork the surface gently around emerging bulb tips to stop them smothering. Feed bulbs with a light dressing of sulphate of potash as the noses appear.

Spring. Never cut or tie bulb foliage. Leave it for six weeks after flowering, until it yellows, and let the emerging asters and sedums do the concealing for you. This is the whole point of the layering.

Late summer. Water sedums and asters in dry spells while they are in bud, and give the taller asters a discreet stake or twiggy support in June. Divide congested clumps every third autumn, replanting the outer, healthier growth and working fresh compost into the hole.

Do this once, properly, and the border genuinely will carry you from January snowdrops to October asters without a single dead fortnight in between.