Planting spring bulbs: what, when and how deep

Spring bulbs are the closest thing gardening offers to a guaranteed result: plant a healthy bulb at the right depth in autumn and it will almost certainly flower. Yet plenty of gardeners end up with tulips rotting in wet soil, daffodils that come up blind, or pots excavated by squirrels before Christmas. The fixes are simple, and they mostly come down to depth, timing and a little planning in September and October.

The depth rule: three times the height of the bulb

The single most useful rule in bulb planting: dig a hole three times as deep as the bulb is tall, measured to the base of the bulb. A 5cm daffodil bulb sits with its base about 15cm down; a small crocus corm needs only 7–8cm; big tulips want 15–20cm. Pointed end up, flat basal plate down — and if you genuinely cannot tell (some corms are ambiguous), plant on its side and the shoot will find its own way.

Shallow planting is the more common error and the more damaging one. Bulbs planted too near the surface are more likely to be frosted, dried out, dug up by squirrels, or — particularly with tulips and daffodils — to split into masses of small non-flowering offsets. Deep-planted tulips are also noticeably more likely to return in later years. If in doubt, go deeper; almost no spring bulb resents it.

Timing: why daffodils go in early and tulips go in late

Most spring bulbs — daffodils, crocuses, alliums, fritillaries, hyacinths — are best planted in September or early October, while the soil still holds summer warmth. Daffodils in particular start rooting early, and late-planted ones often flower poorly in their first spring.

Tulips are the deliberate exception: wait until November. Tulips are prone to tulip fire, a fungal disease that disfigures leaves and flowers, and planting into colder soil after the first proper frosts reduces the risk of infection taking hold. The bulbs lose nothing by waiting — tulips root late anyway — and November planting (even into December, if the ground is workable) is standard practice. If you find a forgotten bag of tulips in January, plant them anyway; a late tulip usually still flowers, while a bulb in a paper bag certainly will not.

Wherever you plant, drainage matters more than soil fertility. Nearly all spring bulbs come from climates with dry summers and will rot in ground that stays wet. On heavy clay, plant a little deeper, drop a handful of coarse grit in the base of each hole, or grow the fussier bulbs (tulips especially) in pots instead.

Naturalising bulbs in grass

Daffodils and crocuses drifting through a lawn or orchard are one of the easiest large-scale effects in gardening. The technique:

• Choose robust naturalisers: Narcissus pseudonarcissus (our native wild daffodil), 'February Gold', 'Tête-à-tête', Crocus tommasinianus, snake's head fritillary for damper ground, and Camassia for heavier soil.
• Scatter the bulbs by the handful and plant them where they land — regimented grids look wrong forever. Aim for dense clumps thinning to outliers.
• Use a bulb planter or a spade to lift flaps of turf for groups; a long-handled bulb planter earns its keep beyond fifty bulbs.
• The critical commitment: do not mow until the bulb foliage has yellowed and died down — around six weeks after flowering, which for daffodils means leaving the grass long until roughly late May or June. Mowing early is the main reason naturalised daffodils dwindle. Plan the drift where long grass in May will look meadow-like rather than neglected.

Layered pots: the bulb lasagne

One deep pot can flower continuously from February to May by stacking bulbs in layers, latest-flowering deepest.

1. Choose a pot at least 30cm deep with drainage holes. Put 5cm of crocks and gritty compost in the base (peat-free multipurpose with a couple of handfuls of grit suits bulbs well).
2. Bottom layer, about 20–25cm deep: tulips.
3. Cover with compost, then a middle layer at 10–15cm: daffodils or hyacinths.
4. Cover again, then a top layer at 5–8cm: crocuses, Iris reticulata or dwarf narcissi.
5. Top up with compost, water once, and stand somewhere cool and rain-sheltered; water only sparingly until growth shows in late winter.

Bulbs can sit almost shoulder to shoulder within each layer — far closer than in the ground — and shoots from lower layers simply grow past the bulbs above. Assemble the pot in November so the tulip layer goes in at the right time; the earlier bulbs tolerate November planting better than tulips tolerate September.

Outwitting squirrels

Grey squirrels treat freshly planted bulbs, tulips and crocuses especially, as a buried buffet. Realistic defences:

• Lay chicken wire or fine mesh flat over the planted area (or over the surface of pots), pinned down or tucked under the rim, until shoots emerge in spring. This is the reliable method.
• Plant at full depth and firm the soil back — it is freshly disturbed earth that attracts investigation, so tidy away every scrap of papery bulb tunic from the surface.
• Favour bulbs squirrels ignore: daffodils and snowdrops are unpalatable to them, as are alliums and hyacinths. Where squirrel pressure is severe, a garden of narcissi, alliums and fritillaries will succeed where tulips and crocuses keep vanishing.
• Chilli powder, ultrasonic gadgets and plastic predators have poor track records; wire works.

After flowering: the leaves stay

Next spring's flower is built in the six weeks after this spring's flower fades, using energy the leaves photosynthesise back into the bulb. So:

• Deadhead spent flowers of daffodils and tulips so energy is not wasted on seed, but leave every leaf in place until it yellows and pulls away easily — usually about six weeks.
• Do not tie, plait or knot daffodil foliage. It looks tidier and quietly starves the bulb; blind (non-flowering) daffodils the following year are the usual result.
• A liquid feed such as diluted tomato fertiliser every couple of weeks after flowering helps bulbs in pots and congested clumps rebuild.
• Clumps of daffodils that have gone blind through overcrowding can be lifted as the foliage dies down in June, split and replanted immediately at full depth — they usually flower again within a year or two.

Bulbs that come back — and bulbs that fade

It saves disappointment to know in advance which bulbs are genuinely perennial in UK gardens and which are best treated as annual bedding.

Reliable returners

• Almost all daffodils (H6), which multiply for decades.
• Crocus tommasinianus and Crocus chrysanthus cultivars (H6), which seed themselves around.
• Snowdrops (H5), snake's head fritillaries, Muscari, Scilla, winter aconites (Eranthis hyemalis) and Anemone blanda.
• Among tulips: species and near-species types such as Tulipa sprengeri, Tulipa clusiana and the kaufmanniana and fosteriana groups, plus Darwin hybrids, which persist better than most.
• Allium hollandicum 'Purple Sensation' and most drumstick alliums.

Usually one good year

• Large showy tulips — parrots, doubles, most Triumph types — typically dwindle after their first spring in ordinary garden soil. Deep planting in sharp drainage helps, but many gardeners simply replant favourites each November and treat the survivors as a bonus.
• Prepared (forced) hyacinths flower magnificently indoors once; planted out afterwards they return smaller and looser, pleasant but never the same.
• Very heavily bred "novelty" daffodils with split coronas can also be shorter-lived than the classic trumpets.

If you want a display that improves rather than dwindles, spend most of the budget on daffodils, crocuses, alliums and snowdrops, and treat show tulips as an inexpensive annual indulgence in pots.

Sources and further reading

• Royal Horticultural Society — bulb planting guides, tulip fire advice and cultivar trials
• Garden Organic — organic approaches to bulbs, lawns and spring flower meadows
• Woodland Trust — native spring flowers, including wild daffodils and snowdrops in woodland settings