Fennel

Planting window

When to sow, by microclimate — foggier blocks run a different calendar than sunnier ones.

Sunlight

How well it does at each level of direct sun per day.

Soil depth

Root room it needs — useful for sizing raised beds and containers.

Soil pH

The soil acidity it grows best in — most crops sit just below neutral, so this mostly matters for heavily amended or long-reused beds.

Spacing

Room each plant needs — along the row and between rows — for sizing beds.

Growth habit

The shape it makes in the bed and how tall it gets — what tells you whether to give it a trellis, a stake, or just room.

Habit

Upright

Mature height

1–2.5 ft

Stands on its own; the tallest types appreciate a stake in wind.

Growing in containers

Whether it does well in a pot, planter, or window box — the SF balcony-and-deck question, weighing its footprint, form, and staying power, not just root depth.

Workable in a large, deep container with attentive watering and feeding.

How to start it

Sow it where it grows, or raise it under cover and set it out — and how far ahead to start the seedlings if it's the latter.

Usually

Direct-sow

Start indoors

6 weeks ahead

Sown straight into the bed it will grow in.

Getting started

How it goes in the ground — how deep to sow or set it, and the soil temperature it needs to wake up. The cold-soil floor is the real limiter for direct-sowing in a foggy SF spring.

Started from

From seed

Ideal soil temp

60°F

Sow depth

0.5 in

Time to emerge

7–30 days

Watering & feeding

How thirsty and how hungry it is — the water it wants and how much feeding the bed needs to keep it producing. In the fog belt even a thirsty crop drinks less than it would inland.

Water need

Moderate

Wants steady, even moisture — roughly an inch a week, a little more in a heat spell.

Feeding

Moderate feeder

A balanced feed worked into the bed at planting usually carries it through the season.

Keep consistently moist — dry spells make the bulb split or bolt. A moderate feeder.

Pests & diseases

What tends to trouble this crop — what it is, what you'll see, and what to do about it, least-toxic first.

Generally resistant to most diseases; aphids, thrips, and cabbage-moth larvae can chew the foliage. Manage with insecticidal soap. (Utah State Extension)

Harvest & storage

How to tell it's ready to pick, and how to keep it once it's in.

Keeps

WeeksHolds a week or two in the fridge.

Ready to harvest

Cut the bulb at the base when it's firm and less than about 4 in across, before it starts to bolt.

Storing

Trim the tops and refrigerate the bulb in the crisper; it keeps about a week or two.

Culinary use & nutrition

What it's for in the kitchen, and the nutrients a 100 g raw serving is a notable source of.

Pollinators & wildlife

What this crop offers the garden's wildlife once it flowers — often the payoff for letting a bolting plant stand.

Beneficial insects

Hoverflies, lady beetles, and parasitoid wasps that keep aphids and caterpillars down.

Butterflies

Adult butterflies nectaring, and in some crops the leaves their caterpillars grow up on.

Allowed to bloom it is a proven insectary plant, its yellow umbels feeding hoverflies and predatory wasps, while the foliage itself is nursery for anise swallowtail caterpillars rather than nectar for the adults.

Sources