The Gardener's LogPlanting Spring Bulbs: A Practical Guide for UK Gardens
Spring bulbs are one of the best returns on effort in gardening. An afternoon on your knees in autumn gets you months of colour when the garden is otherwise bare. Most of the mistakes people make come down to planting too shallow, planting in waterlogged soil, or planting at the wrong time. This guide covers the basics for UK gardens.
When to plant which bulbs
Timing varies a little with where you live, but as a general guide:
- Daffodils and narcissi: September to October. They like an early start to build roots.
- Crocus, snowdrop-type small bulbs, scilla and grape hyacinth: September to October. (Snowdrops are often best bought "in the green" in late winter rather than as dry bulbs, which dry out and establish poorly.)
- Hyacinths: October to November.
- Tulips: November is ideal. Planting them later than daffodils helps reduce the risk of tulip fire, a fungal disease that can attack them in cold, damp conditions.
- Alliums: October to November.
So at the end of October you are still well placed for most of them. If you buy bulbs and cannot plant them straight away, keep them somewhere cool, dry and airy, not in a sealed plastic bag where they may sweat and go mouldy.
Choosing good bulbs
Bulbs should feel firm and heavy for their size, with intact papery skins. Reject any that are soft, mouldy or shrivelled. Bigger bulbs generally flower better in the first year. Cheap bulbs are fine, but check them as you would fruit.
Where to plant
Most spring bulbs need two things: sun for part of the day (many flower before trees come into leaf, so ground under deciduous trees is often fine) and good drainage. Bulbs sitting in wet soil over winter will rot. On heavy clay, improve drainage by adding grit or coarse compost to the planting hole, or plant in raised beds or pots instead.
How deep and how far apart
The usual rule is to plant at around two to three times the height of the bulb. A bulb 5 cm tall needs a hole around 10 to 15 cm deep. On light, sandy soil go towards the deeper end, and on heavy soil slightly shallower. Space bulbs roughly two to three bulb-widths apart, closer for a dense display.
Plant with the pointed end up. If you cannot tell which way up it goes, as with some flat or irregular bulbs, plant it on its side and it will find its own way.
Planting in borders
Dig a wide, shallow hole or trench rather than lots of individual holes, and set several bulbs in a group. Groups of seven or more look more natural than single bulbs in rows. Scatter bulbs gently and plant them where they land for a more natural look. Cover with soil and firm lightly. A watering is helpful if the autumn is dry, but you rarely need to in the UK.
Planting in pots
Bulbs do very well in containers, which also helps in wet gardens. Use a peat-free multipurpose compost mixed with some grit for drainage, and make sure the pot has holes and is raised on feet. Put the bulbs closer together than in borders, almost touching, but not quite. Layering - tulips on top, daffodils below, and small bulbs on top - gives an extended display in one pot. Keep pots somewhere they will not become waterlogged and check them occasionally in winter: rain usually keeps them damp enough. For protecting pots from hard frosts, see our post on overwintering pots.
Naturalising bulbs in lawns
Daffodils, crocuses and snake's head fritillaries can look fantastic in grass. Plant them in drifts, using a bulb planter or a sharp trowel to lift a plug of turf, drop the bulb in and replace the plug. The catch is that you must delay mowing that area until the leaves have died back naturally, usually six weeks after flowering, as the leaves feed next year's flowers. If you want a tidy lawn all spring, this might not suit you.
Protecting against squirrels, mice and slugs
Squirrels dig up bulbs, especially tulips and crocuses. A layer of chicken wire pinned over the soil, or a layer of stones, can help. Pots can be covered with mesh until growth appears. Slugs eat new shoots in spring, so keep an eye out.
Looking after bulbs after flowering
Deadhead spent flowers to stop energy going into seed. Leave the leaves to die back naturally - do not cut them off or tie them in knots - because they are recharging the bulb. A liquid feed high in potassium, such as a tomato feed, at flowering time can help perennial bulbs flower again. Daffodils usually come back well year after year, while tulips often decline after the first season and are sometimes treated as annuals.
Poisonous bulbs and handling
Daffodil bulbs are toxic if eaten, so keep them away from pets and children and wash your hands afterwards. Hyacinth bulbs can irritate skin, so gloves are sensible.
A quick checklist
- Buy firm, healthy bulbs.
- Plant at two to three times their height.
- Pointed end up, with good drainage.
- Plant tulips in November.
- Leave leaves to die back naturally.
If you are doing garden clearance anyway this autumn, combine bulb planting with clearing leaves so borders are tidy and the soil is open and ready to plant.