When to plant swiss chard in Baltimore, Maryland

March 10 – March 24

Direct-sow outdoors · typical Baltimore year

Climate basis: NOAA station Md Sci Ctr Baltimore, MD (USW00093784), 1 mi (2 km) from downtown Baltimore (ZCTA 21202 centroid), elevation 20 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 (March 24). One year in ten still freezes after April 4.

Last spring freezeMarch 241-in-10 after Apr 4

First fall freezeNovember 211-in-10 before Nov 7

Frost-free season≈ 244 daysmedian at 32°F

Hard freeze, 28°Mar 11 – Dec 5kills even hardy greens

USDA zone8a10 to 15°F winter low — not frost timing

The Baltimore year

Direct-sow outdoorsMar 10 – Mar 24

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to Apr 4

Swiss chard in Baltimore · freeze context from Md Sci Ctr Baltimore, MD, 1991–2020 normals.

Every method, with its sources

Direct-sow outdoors

Mar 10 – Mar 24

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 (Mar 24). 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.

Keep exploring

This crop, other cities

Related crops in Baltimore

Local overview