Growing Fennel: A Complete Profile
By Growing Home Greens Team · July 18, 2026
Florence fennel, the bulbing kind grown for its crisp, anise-flavored base, is a slow crop and a famously antisocial one. Almost every source on companion planting agrees on the same point: fennel doesn’t play well with much of anything else in the garden.
Starting it, and the long wait for a bulb
Fennel can be started indoors five weeks before last frost or transplanted out about two weeks after it, and at 90 days to maturity it’s one of the slower vegetables in a typical garden. The bulb forms at the base of overlapping leaf stalks, above the soil line, and needs consistently moist soil to bulb up properly without splitting or bolting.
The problem is where you plant it, not how
The most common issue isn’t a growing problem at all. It’s placement. Fennel root exudates are widely reported to stunt tomatoes, beans, and peas, and it’s broadly reported to be a poor neighbor for brassicas like kale and broccoli. It also cross-pollinates with dill, which degrades the flavor and seed quality of both if they’re allowed to flower near each other.
Give it its own bed, not a shared one
Fennel has no confirmed companions and a long list of plants it’s better kept away from (see the full companion guide for fennel). Given how widely it’s reported to be a poor neighbor, the simplest approach in the Garden Designer is to give fennel its own isolated spot at a bed edge rather than trying to work it into a mixed planting.
Companion planting guide for Fennel (Florence/bulbing) · Find your planting dates
Typically viable in USDA zones 4-9. Not sure your zone? Look it up by ZIP code.
Mature height: 2-3 ft
Method: Either: Start indoors for an earlier harvest, or direct-sow outside for less fuss. Either works.
When to plant fennel (Florence/bulbing), by zone
Every zone fennel (Florence/bulbing) grows in. Pick your zone in the header and it will be highlighted here. Each zone links to its full page.
| Zone | Start indoors | Sow or plant out | Harvest |
|---|---|---|---|
| 4a & 4b | Apr 10–Apr 17 | May 29–Jun 5 | Aug 27–Sep 3 |
| 5a & 5b | Apr 5–Apr 12 | May 24–May 31 | Aug 22–Aug 29 |
| 6a & 6b | Mar 21–Mar 28 | May 9–May 16 | Aug 7–Aug 14 |
| 7a & 7b | Mar 6–Mar 13 | Apr 24–May 1 | Jul 23–Jul 30 |
| 8a & 8b | Feb 18–Feb 25 | Apr 8–Apr 15 | Jul 7–Jul 14 |
| 9a & 9b | Jan 11–Jan 18 | Mar 1–Mar 8 | May 30–Jun 6 |
Harvest dates are about 90 days after the sow or plant-out date, not after starting seeds indoors.
See exact start-indoors, direct-sow, and harvest dates for your zone →
How many Fennel (Florence/bulbing) plants fit per square foot?
Spacing: 1 per square foot (square-foot-gardening spacing). Mature height: 2-3 ft.
Varieties worth considering
- Zefa Fino: Utah State University Extension names Zefa Fino, alongside Orion Hybrid, as a commonly grown Florence fennel variety with a compact form, thick leafstalks, softball-sized bulbs, and resistance to bolting. (source)
- Orion Hybrid: The other variety USU names alongside Zefa Fino, sharing the same compact form, thick leafstalks and bolt resistance. Independent Pacific Northwest trial data found both had good bulb production in only one of two trial years, a reminder that even the bolt-resistant varieties are weather-dependent, not bolt-proof. (source) Buy seeds: Burpee · High Mowing Organic Seeds
- Orazio (F1): Johnny's own hybrid, bred for large, thick, rounded bulbs and higher yield than the flatter open-pollinated types above. Recommended for a fall harvest timed to shortening, cooling days, the same timing discipline that keeps any fennel from bolting. (source)
Why each variety is listed comes from the source shown next to it. We haven't grown these ourselves yet, so treat this as a research-backed starting point, not a personal endorsement. The buy links are separate from those sources: they go to seed suppliers that sell that exact variety, and we may earn a commission on some of them.
Where to buy fennel seeds
Botanical Interests · True Leaf Market · Burpee · High Mowing Organic Seeds (each supplier's fennel seeds)
The varieties we recommend above each have their own buy links, for the suppliers that sell that exact variety.
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See it growing
Search YouTube for "growing fennel (Florence/bulbing)" videos → (a live search, not a hand-picked video; results vary and aren't vetted by us)
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Growing Fennel (Florence/bulbing): A slow-maturing bulb crop that's also one of the worst neighbors in the garden. Plan its spot in isolation, not the middle of a mixed bed.
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