Growing Crocus in a pot
For balcony, patio or terrace — Crocus vernus
crocus grows well in a pot of at least Ø 20 cm (6 L capacity), in a position with full sun or partial shade. Watering: 1-2x per week in summer, only when dry in winter.

Which pot?
Ø 20 cm
~ 6 L potting soil
Give the plant room with a pot slightly wider than the current rootball, with matching depth.
Watering
1-2x per week
only when dry
Always use a pot with drainage holes. Water dries out faster in pots — or the plant drowns. Check weekly with your finger: only water when the top 2 cm of soil is dry.
Pot care
Crocus vernus is one of the easiest bulbs you can grow, demanding very little once established. Water needs are low; the corms are adapted to dry summers and rely mainly on autumn and winter rainfall. In a typical year you won't need to water at all, though if autumn planting coincides with a prolonged dry spell, a light watering after planting helps settle the corms in. Avoid watering during the summer dormancy period, as moisture at this time can encourage rot. Feeding is not necessary. Crocuses are light feeders and will perform reliably year after year in ordinary garden soil without supplementary fertiliser. If you wish to give them a modest boost, a light sprinkling of bonemeal mixed into the soil at planting time is sufficient, but even this is optional rather than essential. Crocuses are fully hardy across temperate Europe (zone 3a–8b) and need no winter protection. The corms remain dormant underground through summer and autumn, then produce roots in autumn and flowers in late winter or early spring. Leave them undisturbed; they naturalise well and will gradually multiply into larger clumps. Pests are few. Mice, voles, and squirrels occasionally dig up and eat newly planted corms, so if this is a problem in your garden, cover the planting area with wire mesh until the soil freezes. Sparrows sometimes peck at the flowers, particularly yellow varieties, though damage is usually minor. Slugs rarely bother crocuses. Diseases are uncommon, but corms will rot in waterlogged soil, so good drainage at planting time is your best prevention. A light mulch of leaf mould in autumn helps suppress weeds without impeding the emerging shoots.
Pot-specific tip: add slow-release fertiliser pellets in March — potting soil exhausts much faster than open ground.