Zone 4a Planting Calendar: What to Plant Each Month
The coldest night of the winter averages -30°F to -25°F in zone 4a. Where it is, when its frosts come, and what to do in the garden each month, from extension service guidance.
Where zone 4a is
Zone 4a covers 814 ZIP codes in 15 states: North Dakota (316), Minnesota (200), Wisconsin (73), Montana (71), Alaska (31), New York (29), Maine (26), South Dakota (24) and 7 more.
Across its 182 NOAA stations the last spring frost comes around May 13 and the first fall frost around Sep 27; half the stations fall between May 10 and May 19 in spring and Sep 23 and Sep 30 in fall.
Cities and towns in zone 4a
- Fargo, ND 58102
- Bismarck, ND 58501
- Grand Forks, ND 58201
- Caribou, ME 04736
- Minot, ND 58701
- Aberdeen, SD 57401
- Williston, ND 58801
- Lake Placid, NY 12946
- Moorhead, MN 56560
Tap a town for its own frost dates and this month’s jobs; a hill or a valley a few miles off can be half a zone either side.
Zone 4a planting calendar
What to start, sow, plant, divide, prune, mulch and protect in zone 4a, month by month. Every job names the extension service page it rests on; open “Where this comes from” under a job to read their words.
Timed from the median frost dates of the 182 NOAA stations in zone 4a: last spring frost May 13, first fall frost Sep 27. Your own ZIP’s frost dates move every window, so the ZIP tool times them for you.
Pick a month above to see every job in it.
The year at a glance
- Start vegetable seeds indoorsFeb to May
- Sow vegetables in the gardenApr to May
- Sow the fall vegetable gardenJun to Aug
- Set out transplantsApr to Jun
- Plant trees and shrubsApr 1 to May 27 and Sep 13 to Nov 1
- Plant garlicSep 13 to Oct 18
- Plant tulips and other spring bulbsOct 4 to Oct 11
- Divide fall-blooming perennialsApr 22 to Jun 3
- Divide spring and summer-blooming perennialsAug 16 to Sep 27
- Prune trees and summer-flowering shrubs while dormantMar 4 to Apr 15
- Prune spring-flowering shrubs after they bloomApr 29 to Jun 24
- Water evergreens and new plantings until the ground freezesAug 30 to Nov 8
- Mulch perennial crowns once the ground freezesNov 8 to Nov 22
- Pull back the winter mulchMar 25 to Apr 8
- Put hardware cloth around young tree trunksSep 27 to Nov 8
- Dig and store canna, dahlia and gladiolusSep 27 to Oct 4
- Cut back perennials after a hard freezeOct 4 to Nov 1
What grows in zone 4a
Perennials, shrubs, trees and fruit that NC State Extension rates as hardy in zone 4a, each linked to its plant page. A plant rated for a range of zones suits every half zone in it, so “zones 4 to 8” covers 4a through 8b.
Perennials 13
- Purple coneflowerzones 3a to 8b
- Orange coneflower (black-eyed Susan)zones 3a to 9b
- Daylilyzones 3a to 9b
- Hostazones 3a to 9b
- Woodland sagezones 4a to 8b
- Coral bells (American alumroot)zones 4a to 9b
- Butterfly weedzones 3a to 9b
- Blue false indigozones 3a to 9b
- Yarrowzones 3a to 9b
- Garden phloxzones 4a to 8b
- Siberian iriszones 3a to 8b
- Showy stonecrop (sedum)zones 4a to 9b
- Rose mallowzones 4a to 9b
Shrubs 8
- Smooth hydrangeazones 3a to 9b
- Common lilaczones 3a to 7a
- Japanese spireazones 3a to 8b
- Arrowwood viburnumzones 2a to 8b
- Red twig dogwoodzones 2a to 7b
- Winterberry hollyzones 3a to 9b
- Catawba rhododendronzones 4a to 8b
- Black chokeberryzones 3a to 8b
Trees 5
- Red maplezones 2a to 9b
- Eastern redbudzones 4a to 9b
- Paper birchzones 2a to 7a
- Colorado blue sprucezones 2a to 7a
- Serviceberryzones 3a to 8a
Fruit 6
- Applezones 4a to 9b
- Pearzones 4a to 8b
- Sweet cherryzones 3a to 8b
- Highbush blueberryzones 3a to 8b
- Red raspberryzones 4a to 8b
- American persimmonzones 4a to 9b
Ratings from the NC State Extension Gardener Plant Toolbox, read Oct 9, 2026. The zone covers winter cold only; heat, rain and soil decide the rest.
The zones next to 4a
Each half zone is five degrees. Zone 3b is five degrees colder at -35°F to -30°F. Zone 4b is five degrees warmer at -25°F to -20°F.
Zone 4a questions
Your own dates, by ZIP
Sources. USDA Plant Hardiness Zone Map, ZIP code tables (2023 and 2012), PRISM Climate Group, Oregon State University; USDA Plant Hardiness Zone Map; USDA Unveils Updated Plant Hardiness Zone Map (USDA Agricultural Research Service, November 15, 2023); NOAA NCEI U.S. Climate Normals 1991-2020, annual/seasonal, by station (v1.0.1); NC State Extension Gardener Plant Toolbox. Zone frost dates are the medians of the NOAA 1991 to 2020 station normals inside the zone.
The calendar’s extension sources:
- UNH Cooperative Extension, Growing Vegetables: When to Plant your Vegetable Garden, read Sep 21, 2026.
- University of Minnesota Extension, Planting vegetables in midsummer for a fall harvest, read Oct 9, 2026.
- University of Illinois Extension, Planting a fall vegetable garden (Good Growing), read Oct 9, 2026.
- University of Minnesota Extension, Dividing perennials, read Oct 9, 2026.
- Iowa State University Extension and Outreach, How should I prepare my perennial beds for winter?, read Oct 9, 2026.
- University of Minnesota Extension, Pruning trees and shrubs, read Oct 9, 2026.
- Rutgers NJAES Cooperative Extension, Pruning Flowering Shrubs (FS1221), read Oct 9, 2026.
- University of Maryland Extension, Planting a Tree or Shrub, read Oct 9, 2026.
- University of Wisconsin-Madison Division of Extension, Preparing Landscape Plants for Winter, read Oct 9, 2026.
- University of Wisconsin-Madison Division of Extension, Storing Tender Bulbs for Winter, read Oct 9, 2026.
- Iowa State University Extension and Outreach, All About Tulips, read Oct 9, 2026.
- UF/IFAS Gardening Solutions, Tulips, read Oct 9, 2026.
- UF/IFAS Gardening Solutions, Preparing the Landscape for Cold Weather, read Oct 9, 2026.
- UF/IFAS Gardening Solutions, Treating Cold-Damaged Plants, read Oct 9, 2026.