When to plant bulb fennel in Austin, Texas
March 10 – March 24
Direct-sow outdoors · typical Austin yearClimate basis: NOAA station Austin 6s, TX (USC00410431), 3 mi (5 km) from downtown Austin (ZCTA 78701 centroid), elevation 570 ft, on the 1991–2020 climate normals. Direct-sow bulb fennel from approximately the dates above, anchored to the median last spring 32°F freeze (March 10). One year in ten still freezes after March 31.
The Austin year
- indoors under lights
- in the garden
- frost-free season
- 1-in-10 years still freeze to Mar 31
Every method, with its sources
Start seeds indoors
Jan 27 – Feb 10Wisconsin Horticulture (University of Wisconsin-Madison Division of Extension) states "Plants can be started indoors 4 to 6 weeks before the last spring frost," giving a sowing span from six to four weeks ahead of the last frost; no competing extension figure was found, so it is encoded as printed. Anchored to the median last spring freeze (Mar 10). University of Wisconsin-Madison Division of Extension (Wisconsin Horticulture)
Direct-sow outdoors
Mar 10 – Mar 24The same Wisconsin Horticulture article says to "Sow seeds about ¼ inch deep after the last frost in spring, or in mid-summer for a fall crop of Florence fennel," and the first clause is a point rule at the last frost that opens a 14-day sowing span; the article's mid-summer alternative is a fixed-calendar rule with no frost relation and so was not encoded. Anchored to the median last spring freeze (Mar 10). University of Wisconsin-Madison Division of Extension (Wisconsin Horticulture)
Variety assumption: Assumes a bulbing Florence type (finocchio) rather than the non-bulbing herb fennel grown for leaf and seed; the cited article covers Foeniculum vulgare generally but names Florence fennel explicitly in its sowing sentence.
These windows describe typical years (1991–2020 climate normals), not this year's forecast. Freezes happen outside them — especially in frost pockets, valleys, and urban edges. Watch the forecast before committing tender plants.
Crop rule sources (1)
- University of Wisconsin-Madison Division of Extension (Wisconsin Horticulture): Fennel, Foeniculum vulgare, Susan Mahr (accessed 2026-07-25)"Plants can be started indoors 4 to 6 weeks before the last spring frost."