Fennel - SARE

Foeniculum vulgare (Apiaceae or carrot family)

Production

Soil preparation

Fennel should not follow after other members of the carrot family, nor after potatoes, cereals or cucurbits, due to possible weed problems.
Fennel does well after early lettuce and greens.
Apply compost and other amendments based on the results of a soil test.
Spread lime as needed to increase both the pH and Ca levels. Dolomite lime will also increase Mg levels. Spread gypsum when calcium levels are low but pH is correct.
A fertilizer company can add OMRI-listed potassium sulfate to compost if it doesn't have enough K to meet the crop’s needs. If this isn’t possible, spread the correct amount of fertilizer and incorporate it before planting. Alternatively, you can side-dress it during cultivation. Divide the recommended rate of the soil test in half if side-dressing.
Incorporate compost and amendments, and plant fennel in raised beds.
Direct-seeded fennel requires a fine and firm seedbed. Prepare the land a few weeks in advance to provide the opportunity for some initial weed control via shallow cultivation or flaming.
Alternatively, place a silage tarp over the prepared and irrigated seedbed 3–5 weeks in advance of the seeding date, depending on the time of year. This will flush many annual weed seeds and reduce weed pressure. Remove the tarp when the weeds have died.

Common recommended fertilizer rates¹

Nitrogen	Phosphorus	Potassium	pH
90	0-160	0-200	6.0-6.4
¹Rates are for New York and are from Cornell University’s Nutrient Guidelines for Commercial Vegetable Production (2019). Check the Cornell website for updated guidelines, or consult with local experts for recommended rates outside New York.

Varieties

Washington State variety trial

Greenhouse guidelines

EZ Seeder seeding plate #9

Cell pack tray	Germination temp	Growth temp	Hardening off	Notes
128	70°–85°	65°–75°	Withhold water	Seed 2 seeds per cell and remove 1 after emergence. Add more vermiculite to the mix to increase drainage. Keep warm, since low temperatures can cause bolting. Put plug trays on a wire mesh bench to encourage air pruning.before planting in field.

Signs to watch for and what to do

Consider a warmer location when plants are too small and don’t develop well. Fennel doesn’t require much water in its earlier stages, but later this changes. You might also require additional fertilization.
Harden plants off outside; plants that are lush don’t perform well in the field.

Transplant tips

Plants that lose some of their root system when replanted have a higher incidence of bolting.
Fennel requires warm and relatively weed-free soil. Transplant early fennel and consider direct seeding for later plantings, if soil conditions allow.

Transplanting in 5- or 6- foot raised beds

Rows	In-row spacing	Planting depth (inches)	Notes
2	9 inches	As deep as the plant can tolerate without the growing point getting buried	Irrigate after planting.

Direct seeding information

Seeder	Rows	Seeds per foot	Seed plate no.	Depth (inches)	Sprocket setting	Notes
MaterMacc	2	6	96 H 1.0	1/4-1/2	22-17
Jang	2	3	YX6		Front 14/rear 10

Cultivation procedures

Use a basket weeder or wheel hoe when weeds are in the white thread stage, without burying the young crop. Weed control is more effective when you eliminate weeds before they emerge.
Use a finger weeder in combination with side knives for the second cultivation. Alternatively, use side knives by themselves to avoid crop damage. Don’t hill fennel, as this makes harvest more difficult and will increase basal rot.
Thin to 9-inches apart and weed the rows to produce large bulbs.

Insect and disease protection

Root and crown rot (Rhizoctonia solani, Pythium spp., and Fusarium spp.): Overhead irrigation and poor drainage in combination with cold soil conditions contribute to plants being affected by these pathogens. Good crop rotation and good hygiene (removing discarded plants from the field) are important as preventive measures. Transplanting when the soil is over 60° and dipping plants in Trichoderma harzianum (as in the product RootShield) are other good preventive measures.

Other cultural practices

Irrigate frequently for optimum yield and plant health. Fennel benefits from drip irrigation. Frequency depends on soil type, evaporation, precipitation and the particular needs of the crop.

Double cropping and/or cover cropping

You can plant a short-season vegetable crop like spinach or arugula after early-planted fennel.

For later dates, work under any harvest remains to avoid insect or pathogen buildup, and plant a cover crop. In the northern United States and Canada, you can follow summer- and early-fall-harvested fennel with a cover crop of oats and peas in September, or rye and vetch planted at later dates. Adjust accordingly in other regions.

Harvest

Yield	1 bulb per row foot
Standards	Harvesting¹ 50 bunches per person per hour.
Standards	Washing 150 bulbs per hour
Tools and supplies needed	Sharp knives and plastic boxes (1 ⅓ bushel or 1 ¾ bushel)
¹Harvest rates don't include the time required to transport crops from the field to a wash and pack shed or storage facility.

Ready-to-harvest and quality indicators

Harvest when fennel has filled out to a bulb that weighs about 1 lb. and has a diameter of at least 4 inches.
Stems should be succulent and free from any defects.

Harvest and washing procedures

Wash hands and sanitize knives before harvesting.
Harvest in the morning hours to avoid field heat accumulation.
Don’t let fennel bulbs overheat. Hydrocooling is recommended, if possible.
The plant is cut at the root. Hold the knife in a level position so the stem being cut is nice and smooth at the bottom. If the immediate outside leaves are affected by crown rot, cut slightly higher so those are easily removed.
In the field, a second person cuts off extra leaves measured to the length of the box. The same person packs and loads boxes on the truck.

Washing and packing procedures

Wash hands and rinse boots before entering the wash-and-pack shed, and cover up field clothes with a bib. If a long-sleeve shirt contains soil, remove this as well.
Bulbs brought back to the shed are free from blemishes or soft spots, and only need light washing by spraying off the bottom part of the bulb.

Additional resources

Packing and storage summary for fennel

Packing in the field	Plastic 1⅓ bushel boxes or 1 ¾-bushel boxes, with 15 bulbs per box
Packing for delivery	The industry standard is 18, 24, 30 or 36 count in a ½-bushel or 1 ⅑-bushel box.
Storage	At 32° and 90–95% humidity

This material is based upon work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture through the Sustainable Agriculture Research and Education (SARE) program. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and should not be construed to represent any official USDA or U.S. Government determination or policy.