Gadenin日本語Get the appThe shape of the crocus year
Crocus run on a short, front-loaded cycle. They are in growth for roughly four months, in flower for two or three weeks of it, and dormant for the rest of the year. Because the flowering window is so brief and so early, almost all of the work that determines how good it is happens either months before or immediately after.
| Season | What the plant is doing | What you do |
|---|---|---|
| Late summer | Fully dormant underground | Lift and divide congested clumps; plant autumn-flowering kinds |
| Autumn | Rooting once the soil cools | Plant spring-flowering corms, firm the soil, net or plant deep |
| Early winter | Roots developing, no top growth | Nothing; check that netting is still pegged down |
| Late winter | Noses through the soil, buds forming | Lift netting, scatter a light feed, watch for bird damage |
| Late winter to early spring | In flower, opening and closing with the sun | Enjoy it; keep the mower off naturalised areas |
| Spring | Leaves building the new corm and offsets | Feed once, water only in a dry spell, do not cut anything |
| Late spring | Leaves yellowing, corm complete | Once fully yellow, mow or clear away the foliage |
| Summer | Dormant, dry, no roots | Keep the ground dry; avoid irrigating over the colony |
The four decisions that decide the year
Almost everything that goes wrong with crocus traces back to one of four choices, and all four are made at a specific moment. Get these right and the colony looks after itself for a decade.
- How deep you plant, in autumn Three inches (8 cm) is textbook; four to five inches (10-13 cm) is what keeps them out of reach of squirrels and mice. Depth costs nothing and cannot be revisited later without digging the whole planting up, so decide before the corms go in.
- Whether you protect the fresh planting Corms are lost in the first week after planting far more often than at any other time. Firming the soil, clearing the debris and either netting or planting deeper is a single afternoon's decision that determines whether anything flowers at all.
- When you first mow, in late spring The six weeks of green leaves after flowering build next year's corm. Mowing while the foliage is still green is the commonest reason a naturalised colony fades away, and no amount of feeding compensates for it.
- Whether the ground stays dry in summer Dormant corms rot in wet soil. Choosing a free-draining position, adding grit to heavy ground, and keeping summer irrigation off the area is what turns a three-year planting into a permanent one.
If you do only one thing differently this year, hold the mower off the crocus grass until the leaves are properly yellow. It is free, it takes no work, and it has more effect on next spring's display than feeding, dividing and replanting put together.
Think in five-year spans, not single seasons
The first spring after planting is the least impressive one a crocus colony will ever give you. Each corm produces one to a few flowers and the patch reads as thin. From the second year the offsets that formed underground start to reach flowering size, and from the third or fourth the count roughly doubles again.
Left alone in grass or rough ground, with the mowing timed correctly, a colony keeps thickening and also creeps outwards through self-sown seedlings until it reads as a sheet of color rather than a group of plants. That takes five to ten years and it cannot be hurried by planting more densely at the start, because a crowded planting simply reaches the point of congestion sooner.
The counterpart is knowing when to intervene. Somewhere between five and eight years a clump in good soil becomes congested: lots of leaves, few flowers. That is the signal to lift and divide in dormancy, and the corms you get out of one clump will start three or four new colonies.
The records that make this calendar yours
General calendars talk in seasons because they have to cover every climate. Your own garden runs on dates, and four of them are worth writing down every year: the date you planted, the date the first flower opened, the date the last flower finished, and the date the leaves finally turned yellow.
Those four numbers give you your own flowering window, your own mowing date and your own planting-to-flowering interval, all of which are far more accurate than any general guidance. Add the position and size of each colony, the number of corms planted and the count you get back at each division, and after three years you have a record that tells you exactly which parts of your garden crocus want to be in and which they do not.