When to plant fennel?
Sow Florence fennel outdoors in June or July, and indoors from late spring, planting out from early May, because early sowings bolt. Campania's written transplants are September and October, and Sicily's are April-May or September-November, once the soil stays above 10-12 °C.
When, by region
| North | Centre | South | |
|---|---|---|---|
| Sowing | Outdoors in June or July, about 15 mm deep, once the weather has warmed. Indoors from late spring, one seed a module. Outside from early May, after the last frost. The bulb takes three or four months, or about six weeks if you cut it small. | Umbria's 2025 guide does not fix a month. No repeat crop: return after at least 3 short cycles, or after 1 year. No other umbellifers in between. | In Campania the transplants are in September and October, with harvests from winter through the whole of the following spring. Around 4 °C the plant stops. In Sicily, April-May or September-November, once the soil stays above 10-12 °C and frost is finished. |
| Spacing | Rows 30 cm apart, plants 30 cm apart. For small bulbs, 10-15 cm, cut at about 5 cm. In a pot about 40 cm wide, up to three mature plants. The bulb is usually cut at 10-15 cm across. | As in the north for the RHS. Umbria does not write a spacing. | In Campania, 7-10 plants per square metre. Transplanting is the usual method. In Sicily, in the open, rows 30-40 cm apart, plants 20-30 cm apart, seed 2-3 cm deep. In a seedbed, 1 cm deep, and out at 10-15 cm with at least 2-3 true leaves. |
Drought, and cold while the plants are young, send them to flower. The bulb wants even water.
June or July, indoors from late spring, early May, 15 mm (½ in), 30 cm (1 ft), 10-15 cm (4-6 in), 5 cm (2 in), a 40 cm (16 in) pot, the three or four months and the six weeks are from the RHS. Nights on average above 10-13 °C (50-55 °F), on the bolting page, cover Florence fennel along with radicchio and oriental greens. September and October, 4 °C and 7-10 plants per square metre are from Campania. April-May, September-November, 10-12 °C, 30-40 cm, 20-30 cm, 2-3 cm, 1 cm and the 70-100 days from transplanting are from Sicily. The 3 short cycles or the year with no other umbellifers are from Umbria 2025, which does not fix a month. Celery, same family, is in when to plant celery. The months are in the April calendar, May, June, July, September, October and November.
June and July, not earlier
The RHS sows outdoors in June or July, once the season has warmed. Earlier, the plant flowers and the bulb does not form, or it turns woody. To get ahead, sow indoors from late spring, one seed a module: Florence fennel suffers if the roots are disturbed. Outside from early May, after the last frost, at the same depth as before, 30 cm (1 ft) apart.
The drill is about 15 mm (½ in) deep. Rows 30 cm apart. Thin to 30 cm, without shifting the plants that stay. For mini bulbs, 10-15 cm (4-6 in), and cut when the bulb is about 5 cm (2 in). A full bulb is usually cut at 10-15 cm across, in late summer and autumn, before the stem stretches. It takes three or four months, or about six weeks for the small ones. The single module is in starting seeds indoors.
The southern months
In Campania the crop runs from autumn into spring. The written transplants are September and October, and the harvests carry from winter through the whole of the following spring. Around 4 °C growth stops. Very high temperatures slow the bulb or stop it, because the plant flowers early. The usual method is transplanting, 7-10 plants per square metre. A sowing month, beyond those two transplants, is not written.
In Sicily, transplant once the soil has settled above 10-12 °C and frost is finished: in spring, April-May, or in autumn, September-November. Open-ground sowing is written as an unusual method: rows 30-40 cm apart, plants 20-30 cm apart, seed 2-3 cm deep. In a seedbed, 1 cm deep, and transplant at about 10-15 cm with at least 2-3 true leaves. The bulb is ready 70-100 days from transplanting, at about 10-15 cm. The plant stands cold and fears a hard frost. The pH they give is between 6 and 7.
In Umbria, in 2025, there is no month. It is not repeated. Return after at least 3 short cycles, or after 1 year, and no other umbellifers go in between. In Sicily, between two repeats, the crop in the middle must belong to a family other than the composites. Parsley and celery are in when to plant parsley and when to plant celery.
Even water, or no bulb
The soil must not dry out. Drought sends it to flower. So do a cold spring, and disturbed roots. On the bolting page, the RHS puts Florence fennel with radicchio and oriental greens: they flower when nights turn warm, on average above 10-13 °C (50-55 °F). Once the base swells, earth it up, so the bulb stays white. How much is in watering.
A pot about 40 cm (16 in) wide holds up to three mature plants, or more if you cut them small at 10-15 cm. The compost dries out fast, and drought ruins the crop. See the container garden. In crop rotation fennel sits with the roots, along with carrot, celery and parsley. In Campania, outside mountain zones, the rotation is five years, with at least three crops and at most one repeat.
In the app
Every plant in the catalogue has its own sowing calendar, and weather alerts for your area help you judge whether to sow now or hold off.
Frequently asked questions
When do I sow in the north?
Outdoors in June or July, about 15 mm deep. Indoors from late spring, one seed a module, and out from early May. Before June, outdoors, the RHS expects it to bolt. Plants 30 cm apart, rows 30 cm apart.
What months does Campania write?
Transplants in September and October. Harvests from winter through the whole of the following spring. Around 4 °C growth stops. Density 7-10 plants per square metre. A sowing month, beyond those transplants, is not written.
What about Sicily and Umbria?
In Sicily, April-May or September-November, once the soil stays above 10-12 °C. Seed 2-3 cm deep in the open, 1 cm in a seedbed. Harvest at 70-100 days, bulb about 10-15 cm across. In Umbria no month is written: at least 3 short cycles, or 1 year, and no other umbellifers.
Why is there no bulb?
Usually because it bolted. The RHS names early sowings, a cold spring, disturbed roots and dry soil. On the bolting page, warm nights too, on average above 10-13 °C.
How far apart, and in a pot?
The RHS: 30 cm, or 10-15 cm for bulbs of about 5 cm. Up to three plants in a pot about 40 cm wide. In Campania, 7-10 plants per square metre. In Sicily, 20-30 cm in the row and 30-40 between rows.