Gadenin日本語Get the appSow where it is to flower and nowhere else
Nigella makes a fine taproot within days of germinating, and once that root has gone down the plant will not accept being lifted. A transplanted seedling checks, sits still for two or three weeks, and then either bolts straight to a single short flower on a stunted stem or dies outright. This is not a matter of technique or of being gentle enough; it is how the plant is built. Every other decision about sowing follows from it.
So the seed goes into the ground it will flower in. Scatter it thinly over a raked surface, in drifts rather than rows if you want the informal look the plant is grown for, and rake or sieve a quarter of an inch (5 mm) of fine soil over the top. It needs darkness to germinate reliably, so do not leave the seed sitting on the surface, but do not bury it deeply either. Firm the surface lightly with the back of a rake and water once with a fine rose.
If you have no choice but to start under cover, because of slugs or because the ground is not ready, sow into deep modules or paper pots at two or three seeds each, never into a seed tray, and plant out with the rootball completely undisturbed when the seedlings have two or three true leaves and no later. Beyond that stage the root has already curled at the bottom of the cell and the plant never grows away properly. Direct sowing outperforms this every time.
| Method | What happens | Verdict |
|---|---|---|
| Direct sown where it is to flower | Deep taproot, full-size branching plant, flowers on schedule | The only method that gives the plant its proper size |
| Deep modules, planted out very young | Slight check, plant reaches perhaps two thirds the size | Acceptable fallback where slugs take direct sowings |
| Open seed tray and transplanted | Severe check, stunted single-stem plants or losses | Do not do it |
| Bought seedlings in a pack | Roots already curled, plants flower short and finish early | Not worth buying; seed is cheap and quick |
Autumn and spring sowings give you different plants
Where winters are mild, seed sown in autumn germinates while the ground is still warm, overwinters as a small feathery rosette, and comes away in spring with a root system that produces a plant twice the size and several weeks earlier into flower than anything sown in spring. The stems are longer, the plant branches from the base, and it carries far more of the pods that most people are actually growing it for.
The limit is winter wet rather than winter cold. The seedlings stand hard frost well but rot in ground that lies soggy, so autumn sowing is for free-draining soil and open positions. In heavy ground or where the ground freezes and thaws repeatedly, sow at the very start of spring instead, as soon as the surface is dry enough to rake, and accept a smaller plant. Germination is best in cool soil, roughly 60F to 68F (15C to 20C), and slows badly once the ground is above about 77F (25C), which is why a late spring sowing often disappoints.
Germination takes ten days to three weeks depending on soil temperature, which is slow enough that a bed of freshly sown nigella looks like a failure for a fortnight. Mark the drift with sand or labels so that you do not hoe it off while waiting.
| Sowing time | Soil condition | Result |
|---|---|---|
| Autumn, mild winter areas | Free draining, open, not waterlogged | Largest plants, earliest flowers, most pods |
| Very early spring | Surface workable, soil around 55F to 65F (13C to 18C) | Reliable main sowing, flowers by early summer |
| Mid to late spring | Warming soil | Good succession sowing, flowers through midsummer |
| Early summer | Soil above 77F (25C) | Patchy germination; water the drill before sowing and shade it |
Sow in succession, because each plant is short lived
An individual nigella plant is not a long performer. From the first flower to the last is often only three or four weeks, and then it turns to pods and starts to yellow off. One sowing therefore gives you one short season, however well grown it is. The way to have nigella in flower from early summer to the start of autumn is a series of small sowings rather than a single large one.
Sow a patch every three weeks from the beginning of spring until roughly midsummer. Each sowing wants only a square yard (about one square meter) or a short drift; a whole packet at once is far more than useful. Stop sowing about ten weeks before your first frost, since a plant caught by frost in bud gives neither flowers nor ripe pods.
- Rake a small area and sow thinly Work a patch of a square yard (one square meter) to a fine tilth, broadcast a pinch of seed across it, and sieve a quarter of an inch (5 mm) of soil over the top.
- Label the patch with the sowing date Germination takes up to three weeks and the seedlings are thread-fine. Without a label you will hoe them off or resow on top of them.
- Repeat every three weeks through spring Three or four small sowings spread across spring give you continuous flower for most of the summer. A single sowing gives you a month.
- Stop ten weeks before the first frost Anything sown later flowers thinly or gets caught in bud. In mild winter areas, switch instead to an autumn sowing for next year.
- Let the last sowing run to pods The final patch of the year is the one to leave entirely uncut, so the pods ripen fully for saving and for self-sowing.
Thin harder than you want to
Nigella comes up thick and looks charming as a carpet of fine threadlike leaves, which makes people leave it alone. Unthinned, the plants draw each other up, produce a single weak stem each, flower briefly and then flop as a mass at the first heavy rain. Thin to six to nine inches (15 to 23 cm) apart when the seedlings have their first true leaves, and do it in two passes rather than one so you have some insurance against slugs.
Thin by pinching the unwanted seedlings off at soil level, not by pulling them. A pulled seedling disturbs the taproot of the one next to it, and the neighbor never quite recovers. Do not try to move the thinnings elsewhere; they will not take. At the right spacing each plant branches into a mound eighteen inches (45 cm) across carrying twenty or more flowers, which is far more than a crowded stand produces in total.
Wider spacing also decides the pods. A crowded plant sets a handful of small pods on thin stems; a properly thinned one carries fat, well-striped pods on stems stiff enough to dry standing up, which is the whole point of growing it.
What to write down at sowing time
Record the date of each sowing and the date each one came up, because the gap between them tells you what your soil temperature is doing far better than any calendar does. Two seasons of those pairs and you will know exactly how early you can start. Note where each drift went, too: nigella self-sows, and next spring you will need to tell deliberate sowings from volunteers.
Also note which sowing gave you flowers when. Writing down the first flower date for each successional patch converts a rough three-week rhythm into an exact one for your own garden, so that the following year you can sow to fill the gaps you actually had rather than the ones you assumed.