How to grow Florence Fennel in New Zealand
Florence fennel is grown for its crisp white bulb, which is really the swollen bases of the leaf stalks, with a sweet aniseed flavour raw or cooked. It is quick but fussy: any check from heat, dry soil or root disturbance can make it bolt to flower before the bulb forms. Sow it direct, keep it evenly moist and it will reward you in about three to four months.
📖 Our full guide: How to Grow Florence Fennel in New Zealand
At a glance
When to sow by region
| Region | When to sow | Regional note |
|---|---|---|
| Northland | February to April, August to October | |
| Auckland | February to April, August to October | |
| Waikato & Bay of Plenty | February to April, August to October | |
| Central North Island | February to April, September and October | Skip August in the central North Island. Hard frosts and cold soil stall seedlings, so start in September, under a cloche if you can. |
| Wellington & Lower North Island | February to April, August to October | |
| Nelson & Marlborough | February to April, August to October | |
| Canterbury | September, December to March | Sow Sep, then again Dec to Mar for autumn and winter bulbs. Keep it watered, as dry soil makes it bolt. |
| Otago & Southland | October to December | Sow Oct to Dec once the frosts have passed, so the bulbs have 90 warm days to size up. Autumn sowings run into frost before they bulb. |
| Central Otago | February and March | Sow Feb to Mar and keep it watered; dry soil makes it bolt. Spring sowings meet frosts into early November. |
Not to be confused with: Herb fennel, the tall perennial grown for its leaves and seed, which does not form a bulb.
Where to plant
Grow Florence fennel in full sun in fertile, free-draining soil that holds moisture, dug through with compost. A pH of about 6 to 7 suits it; if your soil is very acid, lime it before sowing.
Fennel bolts when it is stressed, so the aim is steady, unchecked growth. Sow when the weather ahead is mild rather than hot, and sow direct, because the plants dislike having their roots disturbed.
- Northland, Auckland, Waikato and Bay of Plenty, Wellington, and Nelson and Marlborough: sow from February to April for autumn and winter bulbs, and again from August to October. The late summer and autumn sowings are the most reliable, as spring sowings run into summer heat.
- Central North Island: sow February to April, then September and October. Skip August, when hard frosts and cold soil stall seedlings, and use a cloche for early spring sowings if you can.
- Canterbury: sow in September, then again from December to March for autumn and winter bulbs. Keep it watered, as dry soil makes it bolt.
- Otago and Southland: sow from October to December once frosts have passed, so the bulbs have about 90 warm days to size up. Autumn sowings run into frost before they bulb.
- Central Otago: sow in February and March and keep it watered. Spring sowings meet frosts into early November.
Choosing a variety
| Variety | Notes |
|---|---|
| Finale | Bolt-resistant, with large rounded bulbs. A good choice for spring sowings |
| Milano | Early Italian bulb fennel with good bolting tolerance and big white, rounded bulbs |
| Florence (di Firenze, Fennel de Florence) | The traditional heirloom bulb fennel, crisp with a mild, sweet anise flavour |
For spring sowings, choose a variety sold as bolt resistant.
How to plant
- Prepare a sunny bed with plenty of compost and loosen the soil well.
- Sow seed direct, about 1 cm deep, in rows 45 to 50 cm apart, and water with a fine spray. Seed germinates in about 7 to 14 days in soil of 15 to 25°C.
- Thin seedlings to about 30 cm apart, disturbing the roots of the plants that stay as little as possible. The thinnings can go in a salad.
- If you raise seedlings, sow one seed per cell so the whole root ball can be planted without disturbance, and plant out while they are small.
- As the bulbs start to swell, draw soil up around them so they stay pale and tender.
- Sow small batches every few weeks through the sowing window for a longer harvest.
Watering and feeding
Keep the soil evenly moist from sowing to harvest. Dry spells are the main reason fennel bolts or forms a tough, stringy bulb, so water regularly and mulch to hold moisture, but do not keep the soil soggy.
Feed with a liquid plant food every week or two once seedlings are up, to keep growth fast and steady.
Pruning and care through the year
- Keep the bed weeded, as weeds compete for the moisture the bulbs need.
- Protect young seedlings from slugs and snails in damp weather.
- If a plant starts to send up a flower stalk, harvest it straight away and use what has formed, as the bulb only gets tougher.
Harvesting
Bulbs are usually ready about 3 to 4 months after sowing, once they feel firm and are about the size of a flattened tennis ball. Cut them at soil level with a sharp knife. Do not leave them too long, as bulbs left past their best turn woody or split.
You can harvest small bulbs earlier as mini vegetables. The feathery leaves can be snipped at any time as a herb, and the cut stump often sends up a few small shoots you can use the same way.
Growing in pots
Fennel is not ideal for pots, as a pot at least 30 cm wide and deep holds only one plant. If you try it, use quality potting mix, sow two or three seeds in the middle and thin to the strongest, and water often, since pots dry out fast and dry fennel bolts.
Companion planting
Companion advice for fennel is mixed. Traditional lists keep it away from tomatoes, beans and dill, while Yates NZ lists those same plants as companions, and there is little trial evidence either way. What matters most is giving fennel its own space and steady water.
Good companions
Pests and diseases
Florence fennel has few serious problems in home gardens. Bolting from heat or dry soil causes far more failures than pests do.
Pests to watch for
- Aphids Clusters of small soft insects on young shoots and leaf bases. Hose them off or squash them.
- Slugs Seedlings chewed off at ground level and slime trails, mostly in damp weather.
Florence Fennel is rarely troubled by disease.
Common questions
Why did my fennel bolt without making a bulb?
Fennel bolts when growth is checked by heat, dry soil, cold or root disturbance. Sow direct rather than transplanting large seedlings, keep the soil evenly moist, and in the North Island favour late summer and autumn sowings, which grow through mild weather rather than into summer heat. Bolt-resistant varieties such as Finale help with spring sowings.
When should I sow Florence fennel in New Zealand?
In most of the North Island, Wellington and Nelson, sow from February to April, and again from August to October. In Canterbury sow in September and from December to March, in Otago and Southland from October to December, and in Central Otago in February and March.
What is the difference between Florence fennel and herb fennel?
Florence fennel is grown as an annual for its swollen leaf bases, the bulb. Herb fennel is a taller plant grown for its leaves and seeds and does not make a bulb. They are forms of the same species, so if both flower at the same time they can cross, which matters only if you save seed.
How do I know when the bulb is ready?
Pick it when it is firm and roughly the size of a flattened tennis ball, usually three to four months after sowing. Cut it at ground level. If it starts to elongate or send up a stalk, pick it at once.
Can I eat the fennel leaves?
Yes. The feathery leaves have the same mild aniseed flavour and can be snipped as a herb for salads, fish and dressings at any stage.
Should I mound soil around fennel bulbs?
Yes. Drawing soil up around the swelling bulb keeps it pale and tender. Do it gently so you do not disturb the roots.
Sources we checked: Yates NZ: How to grow fennel; Kings Seeds NZ: Organic Fennel de Florence; Kings Seeds NZ: Fennel Milano; RHS: How to grow Florence fennel.