When to plant swiss chard in Knoxville, Tennessee

March 28 – April 11

Direct-sow outdoors · typical Knoxville year

Climate basis: NOAA station Knoxville Exp Stn, TN (USC00404946), 5 mi (8 km) from downtown Knoxville (ZCTA 37902 centroid), elevation 830 ft, on the 1991–2020 climate normals. Direct-sow swiss chard from approximately the dates above, anchored to the median last spring 32°F freeze (April 11). One year in ten still freezes after April 29.

Last spring freezeApril 111-in-10 after Apr 29

First fall freezeOctober 281-in-10 before Oct 13

Frost-free season≈ 198 daysmedian at 32°F

Hard freeze, 28°Mar 31 – Nov 6kills even hardy greens

USDA zone7b5 to 10°F winter low — not frost timing

The Knoxville year

Direct-sow outdoorsMar 28 – Apr 11

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to Apr 29

Swiss chard in Knoxville · freeze context from Knoxville Exp Stn, TN, 1991–2020 normals.

Every method, with its sources

Direct-sow outdoors

Mar 28 – Apr 11

Purdue: semi-hardy — 2–4 weeks before the last frost; Penn State's earliest sowing Apr 17 (−14 days) is the later start and is used. Anchored to the median last spring freeze (Apr 11). Penn State Extension (York County Master Gardeners) · Purdue University Extension

Start seeds indoors

Not calculated

The cited extension guides do not time an indoor seed-starting window for this crop.

Transplant outdoors

Not calculated

The cited extension guides do not time an outdoor transplanting window for this crop.

Fall planting

Not calculated

No source-backed fall planting rule exists for this crop in the registry, so no fall window is calculated.

Variety assumption: First cutting about 50–60 days from seed (Penn State lists 55); tolerates summer heat better than spinach.

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.

This week, not a typical year:

Crop rule sources (2)

Penn State Extension (York County Master Gardeners): Vegetable Seed Planting Guide (accessed 2026-07-24)
Earliest/latest sowing dates for a May 1 last-frost / Oct 1 first-frost baseline; offsets derived by date difference from May 1. Also days-to-maturity figures.
Purdue University Extension: Indiana Vegetable Planting Calendar (HO-186-W) (accessed 2026-07-24)
Hardiness classes: hardy = plant 4-6 wk before last spring frost; semi-hardy = 2-4 wk before; tender = after average last frost; very tender = at least 2 wk after. Table 2: fall planting at least 4-8 wk before first fall frost.

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