Gadenin日本語Get the appPlant in autumn, in soil that is still workable
Spring-flowering crocus goes into the ground in autumn, any time from the first cooling of the soil until the ground begins to freeze. There is no advantage in rushing it the way there is with daffodils, and no advantage in waiting either. A corm needs roughly six weeks of soil above 40F (4C) to put out roots before the cold shuts it down, and then a long cold period to trigger flowering. Corms planted very late still flower, but often shorter and a week or two behind the rest.
Autumn-flowering crocus is the exception and runs on the opposite clock: those corms are planted in late summer and flower within weeks of going in, before they make any leaves at all. Everything else here applies to them too, except the timing.
A crocus corm is a flattened disc with a papery skin, a rough concave base and a small point or a cluster of shoot buds on top. Plant it point up. If you genuinely cannot tell which way up it is, plant it on its side; the shoot will right itself and you will lose nothing but a few days.
Depth and spacing: shallower than a daffodil, closer together
The standard advice is three times the height of the corm, which puts a crocus at around three inches (8 cm) of soil over the top. That is correct horticulturally and it is also exactly the depth at which a squirrel finds them easiest. Where rodents are a problem, four to five inches (10 to 13 cm) is better: crocus pull themselves down with contractile roots anyway, and the extra depth costs you nothing but a slightly later flowering.
Spacing is where most gardens go wrong. A crocus flower is two inches (5 cm) across and a single corm is not a display. Plant them two to three inches (5 to 8 cm) apart, in groups of at least twenty-five, and preferably far more. Ten corms scattered over a border look like an accident; fifty in a tight patch look deliberate.
| Where they are going | Depth over the corm | Spacing | Points to watch |
|---|---|---|---|
| Open border, no rodent pressure | 3 in (8 cm) | 2-3 in (5-8 cm) | Groups of 25 or more, never a straight line |
| Border with squirrels or mice | 4-5 in (10-13 cm) | 3 in (8 cm) | Net the surface until the ground settles |
| Naturalised in grass | 3-4 in (8-10 cm) | Scattered, 3-4 in (8-10 cm) | Replace turf firmly and tread it down |
| Under deciduous shrubs and trees | 3 in (8 cm) | 2-3 in (5-8 cm) | They flower before the canopy closes over |
| Pots and window boxes | 2-3 in (5-8 cm) | 1-2 in (3-5 cm), almost touching | Gritty potting mix, and the pot must drain freely |
| Heavy clay soil | 3 in (8 cm) | 3 in (8 cm) | Add coarse grit under the corm or they rot |
Crocus want sun while they are in leaf and sharp drainage all year. Under deciduous trees is ideal because they finish before the leaves come out. What kills them is summer wet: a bed that stays soggy while the corms are dormant in summer will empty itself over two or three years no matter how well you planted.
Squirrels and mice will find them within days
Crocus corms are edible and squirrels, mice and voles all know it. The bigger problem is not that they smell the corms through the soil, it is that they see the disturbed ground. Freshly forked, dark, crumbly soil is an advertisement, and a planting can be dug over and emptied within two or three days of going in. Gardeners who report losing every corm almost always lost them in that first week, not over the winter.
So the first job after planting is to make the site look undisturbed. Firm the soil down hard with the back of a rake or with your boot, rake off any loose papery skins and stray fragments of corm, and water the bed in. Then cover the surface with leaf litter, bark or the mulch that was there before, so there is no bare dark patch left.
Where pressure is heavy, cover the planting with wire netting of half-inch to one-inch mesh, pegged flat on the surface or laid an inch under it. Leave it in place all winter and lift it in late winter before the shoots get tall enough to grow through the mesh. Netting is the only method that works every time. Planting deeper works most of the time and needs no maintenance, which is why it is the better default for a large drift.
Chilli powder, blood and bone and similar deterrents wash out with the first heavy rain and do not survive a determined squirrel. Do not rely on them alone for a planting you care about.
Planting a drift in grass
Crocus in a lawn is the planting that pays back the most over time, because a colony left alone in grass will spread by offsets and by seed into a sheet. The technique matters: you want it to look as though nobody planted anything.
- Throw the corms and plant them where they land Scatter a handful at a time over the area from waist height and plant each one roughly where it fell. Move only the ones that landed on top of each other. Hand-placed crocus always reads as planted, however random you try to be, because people do not scatter evenly enough to look uneven.
- Aim for drifts, not an even carpet Concentrate the corms at the center of each drift and let the density fall away at the edges, so the patches merge into plain grass rather than stopping at a line. Throwing more handfuls at the middle than at the margins is enough to produce this.
- Lift a flap of turf for groups, a bulb planter for singles For a group of twenty, cut three sides of a square of turf with a spade, peel it back, loosen the soil beneath and set the corms out before folding the turf down again. For scattered singles, a narrow bulb planter or even a stout dibber is quicker.
- Tread the turf back down hard Firm every flap and every plug back with your full weight, and water if the ground is dry. Loose turf dries out, kills the corms beneath, and leaves an obvious dug patch that invites squirrels.
- Plan the first cut before you plant Crocus in grass needs the mower kept off until the leaves have gone yellow, which is roughly six weeks after flowering. Choose an area you are willing to leave shaggy that long, or the colony will die out within a few years.
Write down what went where
Crocus disappear completely for eight months of the year and leave nothing above ground to mark them. Record the location of every group, the number of corms and the depth you planted at, before you tread the soil back. Doing so is what stops you driving a fork through the colony while planting something else in the summer.
Note the planting date and the date the first flower opened in the spring that follows. The gap between the two is remarkably consistent for a given garden, and after two seasons of records you can predict your own flowering week better than any general guide can. Note the depth too, and whether that group was netted, because the following spring you will want to know which method actually kept the corms in the ground.