Why Deciduous Trees Are the Bulb Planter's Best Friend

Woodland bulbs and deciduous trees have been sharing the same soil for centuries, and the partnership works on a simple rhythm. The tree leafs out in late spring, by which time snowdrops, early cyclamen and bluebells have already flowered and begun to die back. Through the winter months, when light reaches the ground unimpeded, the bulbs have the floor to themselves. In autumn the fallen leaves feed the soil just as the bulbs begin to root. Evergreens offer no such bargain: they cast shade all year and shed acidic needles, so bulbs will survive beneath them but rarely romp.

The real obstacle is not light but soil. Beneath a mature oak, beech or birch, the top 20–30cm is a dense mat of fine feeding roots, and the ground is often dry, dusty and full of obstructions. Planting technique matters far more here than the species list, and the two things that decide success are timing and depth.

Plant in Autumn, but Not Too Late

Dry bulbs are lifted and sold from late August, and the sooner they go back into the ground the better. Aim to have them planted by the end of October, before the first hard frosts and while the soil is still warm enough for roots to form. Bulbs left in a paper bag on a shed shelf until December will still grow, but they will flower late and weakly in their first year.

Cyclamen are the exception. Cyclamen hederifolium corms are dormant in late summer and should go in during August or early September, before autumn growth begins. Snowdrops are famously erratic as dry bulbs; many gardeners buy them "in the green" in March instead, and if you do, tease the clumps apart and replant them the same day.

• Work in small pockets rather than clearing a whole bed — you will do less damage to tree roots.
• Plant in drifts of 25 to 50 bulbs, not in single lines. Nature does not do rows.
• Improve the soil with leaf mould if it is thin, but add no manure and no rich compost. Lean soil suits bulbs; overfed bulbs make floppy leaves and few flowers.

Depth: The Single Most Important Number

The reliable rule is to bury a bulb under two to three times its own height of soil. A snowdrop bulb is roughly 2.5cm tall, so it wants 8–10cm of soil above its nose. A bluebell bulb is larger, and wants 10–15cm. Cyclamen corms are a law unto themselves and sit much shallower.

Err on the side of deeper rather than shallower. Deep bulbs are insulated from frost heave, safer from squirrels, and better able to shrug off a dry summer. They are also less likely to be sliced by a hoe or lifted by accident when you are planting something else. Use a bulb planter for speed, or a narrow trowel inserted vertically and levered back to open a slot. A hand fork works well in rooty ground.

Whatever you use, push past thick roots rather than through them, and never sever anything thicker than a pencil. Firm the soil back, water once to settle it, and leave it alone. No fertiliser is needed.

Snowdrops, Bluebells and Cyclamen: Getting Each One Right

Snowdrops. Plant Galanthus nivalis 8–10cm deep and 5–7cm apart. Singles bulk up into thick clumps within a few years; doubles such as 'Flore Pleno' are slower but longer-lived. They like soil that is damp in winter and shaded in summer, and they resent drying out, so a spot beneath a tree that drops its leaves early is ideal.

Bluebells. Buy native Hyacinthoides non-scripta, not the vigorous Spanish hybrids that swamp it. Plant 10–15cm deep and 10–15cm apart in dappled shade, with plenty of leaf mould. Bluebells seed about freely once settled, but a colony from seed takes years, so start with a decent quantity of bulbs. The foliage must be left for at least six weeks after flowering; cut it early and you lose next year's flowers.

Cyclamen. Cyclamen hederifolium flowers in autumn, C. coum in late winter, and both are superb in dry shade. Plant corms with the smooth, rounded side down and the dimpled top just at or fractionally above the surface, 2–3cm deep and 15cm apart. Mark the spot clearly: dormant corms are all but invisible and easily lost.

Outwitting Squirrels, Cats and Spades

Grey squirrels are the main thief. They home in on freshly disturbed soil and will dig up crocus and tulip bulbs with enthusiasm, and snowdrops when nothing better is on offer.

• Lay galvanised chicken wire flat over the planting area and peg it down flush with the soil. Shoots come up through the mesh; lift it once growth is clear. It is the single most effective deterrent.
• Plant deeper than you would in open ground. A squirrel rarely digs beyond 10cm.
• Water and firm the ground after planting so it does not look newly turned.
• Top with a layer of sharp grit or coarse gravel, which is unpleasant underfoot and hides the scent of disturbed earth.
• Plant into grass or established ground cover where you can; bulbs tucked among roots are harder to find.
• Label the site, or ring it with a few short canes, so you do not slice through it with a hoe or a spade later in the season.

Letting the Colony Build

Woodland bulbs want what woodland gives them: leaf litter in autumn, undisturbed soil, and no competition from hungry summer perennials. Resist the urge to tidy. Do not cut or mow foliage until it has yellowed, which is six weeks or more after flowering. Do not heap mulch against the tree trunk — keep 10cm clear around it — and keep the mulch thin, just leaf mould, nothing rich.

Lift and divide congested snowdrop clumps every few years, straight after flowering while they are still in leaf, and replant immediately. Cyclamen will self-seed into cracks between roots if you leave the seedlings alone. Be patient with the whole enterprise. The first spring will be modest, the third promising, and by the tenth you will have a patch of woodland floor that stops visitors mid-sentence.