When to plant lemon balm in Des Moines, Iowa

April 18 – May 2

Transplant outdoors · typical Des Moines year

Climate basis: NOAA station Des Moines INTL AP, IA (USW00014933), 4 mi (6 km) from downtown Des Moines (ZCTA 50309 centroid), elevation 957 ft, on the 1991–2020 climate normals. Transplant lemon balm outdoors from approximately the dates above, anchored to the median last spring 32°F freeze (April 18). One year in ten still freezes after May 2.

Last spring freezeApril 181-in-10 after May 2

First fall freezeOctober 201-in-10 before Oct 4

Frost-free season≈ 184 daysmedian at 32°F

Hard freeze, 28°Apr 8 – Oct 30kills even hardy greens

USDA zone5b-15 to -10°F winter low — not frost timing

The Des Moines year

Start seeds indoorsMar 7 – Mar 21

Transplant outdoorsApr 18 – May 2

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to May 2

Lemon Balm in Des Moines · freeze context from Des Moines INTL AP, IA, 1991–2020 normals.

Every method, with its sources

Start seeds indoors

Mar 7 – Mar 21

Wisconsin Horticulture sows lemon balm indoors about 4 to 6 weeks before the last spring frost, so the window runs 6 to 4 weeks before that date. Anchored to the median last spring freeze (Apr 18). University of Wisconsin-Madison Division of Extension, Wisconsin Horticulture · Virginia Cooperative Extension, Virginia Tech

Transplant outdoors

Apr 18 – May 2

Wisconsin Horticulture ties lemon balm transplanting to seedling height rather than a date, so the frost anchor comes from Virginia Cooperative Extension's herb publication — whose herb table lists lemon balm — which sets all herb plants out after the danger of severe frost has passed. Anchored to the median last spring freeze (Apr 18). Virginia Cooperative Extension, Virginia Tech

Variety assumption: A hardy perennial that self-seeds freely; these windows apply to first-year plantings from seed or nursery plants.

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)

University of Wisconsin-Madison Division of Extension, Wisconsin Horticulture: Lemon Balm, Melissa officinalis (accessed 2026-07-25)
"Lemon balm can be started from seed sown indoors about 4 to 6 weeks before the last spring frost, although seeds may be somewhat slow to germinate."
Virginia Cooperative Extension, Virginia Tech: Herb Culture and Use (Publication 426-420) (accessed 2026-07-25)
"In addition, many culinary herbs, such as tarragon, can only be propagated asexually; seed-grown plants lack the oils that give them flavor."

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