Gadenin日本語Get the appWhy the corms go in at the end of summer
Saffron crocus runs its year backwards compared with the spring crocus most gardeners know. The corms break dormancy at the end of summer, push flowers in autumn with little or no leaf showing, then grow their grassy leaves through the cold months and feed all winter. That means the planting window is the tail of summer into the first weeks of autumn, while the corms are still dry and dormant and before the flower buds have started moving inside them.
Corms planted late still flower, but often not until the following autumn. They spend the first season building leaves instead. Nothing is lost permanently, but you wait an extra twelve months for the first stigmas, so it is worth getting them in the ground the week they arrive rather than leaving the bag in a shed.
Never buy or plant saffron corms alongside autumn crocus, sold as Colchicum or meadow saffron. Colchicum is poisonous in every part and its corms look similar in a bag. Keep the two in separate containers and label the bed before you plant.
Judging corms before they go in
Size is the single honest predictor of flowering. A corm under an inch (2.5 cm) across will usually make leaves and no flowers in its first autumn. From about an inch and a quarter (3 cm) upward you can expect one to two flowers, and a large corm of an inch and three quarters (4.5 cm) or more may give three or four. Firm is non-negotiable: squeeze each one between finger and thumb and discard anything that gives, smells sour, or shows soft blue-gray mold under the papery tunic.
| Corm width | Flowers expected in the first autumn | What to do with it |
|---|---|---|
| Under 1 in (2.5 cm) | None | Plant at the edge of the bed as a grow-on; it should flower the following year |
| 1 to 1.4 in (2.5-3.5 cm) | One, sometimes two | Plant in the main block |
| 1.4 to 1.8 in (3.5-4.5 cm) | Two to three | Plant in the main block, these carry the harvest |
| Over 1.8 in (4.5 cm) | Three to four | Plant in the main block and mark the position, it will split into a strong cluster |
Depth, spacing and getting them in
Plant deeper than feels right. Four inches (10 cm) is a minimum and six inches (15 cm) is better: deep planting keeps the corm cooler in summer, slows the rate at which it splits into small non-flowering offsets, and puts it out of reach of most rodents. Space them four inches (10 cm) apart in a block rather than a line. Saffron flowers sit close to the ground on short tubes, and a block is far easier to pick over on a cold morning than a scattered drift.
- Dig the whole bed, not individual holes Take out the top eight inches (20 cm) of the planting area rather than making one hole per corm. You want to loosen and improve the drainage of the entire block, and a bulb planter leaves a narrow sump that collects water around each corm.
- Work coarse grit into the base Fork two to three inches (5-8 cm) of coarse grit or sharp sand into the bottom of the excavation and into the soil you removed. On heavy clay, raise the whole bed four to six inches (10-15 cm) above the surrounding level instead of trying to improve it in place.
- Set the corms pointed end up The growing point is the narrow end; the base is flat and often shows the dried remains of last year's roots. If you genuinely cannot tell, lay the corm on its side. It will right itself, at the cost of a few days.
- Backfill and firm, then water once Replace the soil, firm it with your palms rather than your heel, and give one thorough watering to settle it. That is the only watering the bed needs until the leaves are up, unless autumn is exceptionally dry.
- Label the block immediately Saffron leaves are indistinguishable from grass to anyone who did not plant them, and they emerge at a time of year when beds get tidied. A permanent label and a marked corner post prevent the whole planting being weeded out.
Choosing the site: sun, and somewhere that bakes
Give saffron the hottest, driest, most freely drained position you have, in full sun for at least six hours a day. The corms need a hot dry rest through summer, and the fastest way to lose a planting is to put it somewhere that is irrigated through the summer dormancy or that sits wet after storms. A raised bed against a south-facing wall, a gravel garden, or a slope all work. A bed among summer vegetables on a drip line does not.
Containers are a legitimate answer where the summer is wet. A pot at least ten inches (25 cm) deep, in a gritty free-draining mix, can simply be moved under cover once the leaves die back and be left bone dry until the end of summer. The trade-off is that pots split into offsets faster, so expect to tip out and re-grade the corms every second year rather than every fourth.
What to write down on planting day
Note the date the corms went in, how many you planted, their approximate size grade, and the exact position of the block with a measurement from a fixed point such as a fence post. Add the depth you planted at. Three autumns later, when you are deciding whether to lift and divide, that record tells you whether a thin flowering year is age, depth, or simply the smaller grade you bought, and it stops you digging into the block by accident during a spring tidy.