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.

What to expect

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.

Common problems

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.

Where this fits in your garden

Fennel has no confirmed companions in our data 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.

Method: Either — Start indoors for an earlier harvest, or direct-sow outside for less fuss — Fennel (Florence/bulbing) tolerates either.

See exact start-indoors, direct-sow, and harvest dates for your zone →

Spacing: 1 per square foot (square-foot-gardening spacing).

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)

Cited from the source shown next to each variety — we haven't grown these ourselves yet, so treat this as a research-backed starting point, not a personal endorsement.

Where to buy fennel (florence/bulbing) seeds

• Botanical Interests
• True Leaf Market
• Burpee
• High Mowing Organic Seeds

Some links on this page go to retailers we may eventually earn a commission from as an affiliate, at no extra cost to you. We only recommend products with a genuine consensus of positive, independent reviews — see the sources cited on each item.

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)