Landscaping & Garden Hub / Zone 4
Zone 4 landscaping & planting calendar
Zone 4 covers the upper Midwest, northern New England, and much of the Mountain West above the plains, with winter lows to -30°F. Short, intense growing seasons reward planning around the frost windows rather than the calendar.
- Last spring frost
- typically May 10 (Apr 28 – May 25)
- First fall frost
- typically Sep 30 (Sep 17 – Oct 13)
Median across the zone's ZIP codes; ranges cover 8 years in 10. Source: NOAA U.S. Climate Normals 1991–2020. Your own ZIP can run a week or two either side — check yours in the hub.
The Zone 4 year
January
Midwinter watering check
typically mid Jan (late Dec – late Jan)
Midwinter dry spells are when winter drought injury sets in. Monitor conditions and water during extended dry periods without snow cover, about once or twice each month (CSU 7.211) — midday, above 40°F, no snow on the ground. Newly planted trees and evergreens first.
Source: CSU Extension
February
Start slow-growing annuals indoors
typically early Feb (late Jan – mid Feb)
Some annuals need upwards of 16 weeks indoors before transplanting (Iowa State University Extension) — crops on a 12-week schedule get started weeks before the main seed-starting push. Check seed packets for per-variety timing.
Source: Iowa State University Extension
Dormant-prune deciduous trees and shrubs
typically late Feb (mid Feb – mid Mar)
The late dormant season — late winter into early spring — is the best time for most pruning (University of Minnesota Extension). Branch structure is visible before leaves emerge and cuts heal fast once growth starts. Shrubs that bloom on new growth can also be pruned now, before growth begins. Never prune oaks April through October (oak wilt risk).
March
Start vegetable and flower seeds indoors
typically late Mar (early Mar – early Apr)
Most annual flowers and vegetables grown from seed need about 6 to 8 weeks indoors before transplanting (Iowa State University Extension). Count back from your frost-free date, add a week for hardening off, and check each seed packet — some tomatoes need only about four weeks.
Source: Iowa State University Extension
April
Top up pine straw as spring growth starts
typically late Apr (mid Apr – mid May)
Bring beds back to a 2–3 inch layer in early spring, as plants begin to grow and before weed seeds germinate. Keep straw 2–3 inches off stems and trunks; pine needles interlock and hold on slopes better than most mulches.
Source: Clemson Cooperative Extension (HGIC)· How to apply pine straw · How much you need
Apply crabgrass preventer to the lawn
typically mid Apr (early Apr – early May)
Preemergence crabgrass herbicide goes down before the seeds germinate — early to mid-April in southern Iowa, late April to early May in the north (Iowa State University Extension). Nature's cue: apply when forsythia blossoms start dropping or redbuds begin to bloom. Too early and late-germinating crabgrass escapes; too late and some seeds are already up.
Source: Iowa State University Extension
Harden off seedlings before planting out
typically late Apr (mid Apr – mid May)
About two weeks before planting day, harden seedlings by gradually introducing them to outdoor conditions (Iowa State University Extension) — a few hours of sheltered shade at first, working up to full sun and night air.
Source: Iowa State University Extension
Cut blue grama back before spring green-up
typically early Apr (late Mar – late Apr)
Most ornamental grasses benefit from cutting back just before new growth begins in spring — about a month before the last freeze for this warm-season native. Use hedge shears, wear gloves, and leave 2–3 inches of stubble.
Source: CSU Extension
What to plant in April
Planting windows timed from the zone's typical frost dates, from UGA Extension and CSU Extension guides. Open a plant for how to plant it.
Asparagustypically mid Apr (early Apr – early May)
Planting window for Asparagus (Asparagus officinalis). Perennial: set crowns in early spring, 36 in. rows, 18–24 in. apart, 6 in. deep; first harvest in the second year.
Source: UGA Extension
Broccolitypically mid Apr (early Apr – early May)
Planting window for Broccoli (Brassica oleracea var. italica). Hardy cool-season cole crop: set out transplants (started 5–7 weeks ahead) 2–4 weeks before the last frost; space 18 in. Direct seed in midsummer for a fall crop.
Source: CSU Extension
Onion (dry bulb)typically mid Apr (early Apr – early May)
Planting window for Onion (dry bulb) (Allium cepa). Set plants in late winter, or in fall for overwintering short-day types, 18–36 in. rows × 3–4 in.
Source: UGA Extension
Cabbagetypically mid Apr (early Apr – early May)
Planting window for Cabbage (Brassica oleracea var. capitata). Hardy cole crop: transplants 5–7 weeks old go out 2–4 weeks before the last frost at 18 in. spacing; direct seed in midsummer for fall harvest.
Source: CSU Extension
Collardstypically mid Apr (early Apr – early May)
Planting window for Collards (Brassica oleracea var. viridis). Hardy Southern green: sow or transplant in late winter and again in late summer for fall, ½ in. deep, 36 in. rows × 8–16 in.
Source: UGA Extension
Green Onion (bunching)typically mid Apr (early Apr – early May)
Planting window for Green Onion (bunching) (Allium cepa / A. fistulosum). Hardy: sow seed (or sets) 2–4 weeks before the last frost, ¼ in. deep, 2–3 in. apart.
Source: CSU Extension
Kaletypically mid Apr (early Apr – early May)
Planting window for Kale (Brassica oleracea var. sabellica). Hardy green: sow in late winter and again in late summer for fall, ½ in. deep, 36 in. rows × 8–16 in.; sweeter after frost.
Source: UGA Extension
Kohlrabitypically mid Apr (early Apr – early May)
Planting window for Kohlrabi (Brassica oleracea var. gongylodes). Hardy cool-season crop: seed or transplant 2–4 weeks before the last frost, ½ in. deep, 7–9 in. apart.
Source: CSU Extension
Leaf Lettucetypically mid Apr (early Apr – early May)
Planting window for Leaf Lettuce (Lactuca sativa). Hardy: sow 2–4 weeks before the last frost, ¼ in. deep, thin to 7–9 in.; succession plant every 2 weeks for a steady supply.
Source: CSU Extension
Mustard Greenstypically mid Apr (early Apr – early May)
Planting window for Mustard Greens (Brassica juncea). Fast hardy green: sow in late winter and again in late summer for fall, ½ in. deep, 18–36 in. rows × 2 in.
Source: UGA Extension
Garden Peastypically mid Apr (early Apr – early May)
Planting window for Garden Peas (Pisum sativum). Hardy: direct seed 2–4 weeks before the last frost, 1 in. deep, 4–6 in. apart (or 3 in. in 8-in. rows); replant in midsummer for a fall crop.
Source: CSU Extension
Radishtypically mid Apr (early Apr – early May)
Planting window for Radish (Raphanus sativus). Hardy and fast: sow 2–4 weeks before the last frost, ½ in. deep, 2–3 in. apart; succession plant for continuous harvest.
Source: CSU Extension
Snap / Snow Pea (edible pod)typically mid Apr (early Apr – early May)
Planting window for Snap / Snow Pea (edible pod) (Pisum sativum var. macrocarpon). Hardy: direct seed in late winter, 1–2 in. deep, 36 in. rows × 2 in.; trellis taller types.
Source: UGA Extension
Spinachtypically mid Apr (early Apr – early May)
Planting window for Spinach (Spinacia oleracea). Hardy: sow 2–4 weeks before the last frost, ½ in. deep, 4–6 in. apart; replant in midsummer for fall harvest.
Source: CSU Extension
Turniptypically mid Apr (early Apr – early May)
Planting window for Turnip (Brassica rapa subsp. rapa). Hardy cool-season root crop: sow 2–4 weeks before the last frost, ½ in. deep, thin to 4–6 in.
Source: CSU Extension
Chivestypically late Apr (mid Apr – mid May)
Planting window for Chives (Allium schoenoprasum). Hardy perennial onion relative (12–24 in.), zones 3–9, full sun and moist-not-wet soil; late-spring/early-summer blooms draw pollinators — cut stalks back after bloom. Plant bulbs or divisions in fall; divide every three years; contains itself poorly, so cut back or edge.
Source: CSU Extension
Horseradishtypically late Apr (mid Apr – mid May)
Planting window for Horseradish (Armoracia rusticana). Hardy perennial (1–4 ft), zones 3–10, full sun, moist soil; propagate by root division in early spring. Very invasive — grow in a container sunk in the ground. Sap can irritate skin.
Source: CSU Extension
Minttypically late Apr (mid Apr – mid May)
Planting window for Mint (Mentha spp.). Vigorous herbaceous perennial, zones 4–9, sun to part shade, moist well-drained soil; contain with deep edging or a sunken pot; divide every three years in spring or fall. Discard plants showing rust.
Source: CSU Extension
Oreganotypically late Apr (mid Apr – mid May)
Planting window for Oregano (Origanum vulgare). Hardy perennial mint relative (12–36 in.), zones 4–9, full sun and well-drained, slightly alkaline soil; seed in spring or fall, cuttings/division in spring; cut back after summer flowering.
Source: CSU Extension
Sagetypically late Apr (mid Apr – mid May)
Planting window for Sage (Salvia officinalis). Perennial (2–3 ft), zones 5–8, full sun, moist well-drained soil; seed or cuttings in spring; pinch tips the first summer; prune in spring and after late-summer bloom; replace every 4–5 years as it gets woody.
Source: CSU Extension
French Tarragontypically late Apr (mid Apr – mid May)
Planting window for French Tarragon (Artemisia dracunculus). Hardy, drought-tolerant perennial (18–48 in.), zones 3–7, full sun and well-drained soil; garden plants rarely set seed — start from divisions or summer cuttings; divide every 3–5 years; remove summer flowers; cut to the base in fall. Discard plants with rust.
Source: CSU Extension
Thymetypically late Apr (mid Apr – mid May)
Planting window for Thyme (Thymus vulgaris). Low perennial (6–14 in.), zones 4–9, full sun, moist but well-drained slightly alkaline soil, drought tolerant; divide in spring or take cuttings in summer; hard prune by a third to a half in early spring, lightly after summer bloom; do not overwater.
Source: CSU Extension
May
Transplant warm-season starts to the garden
typically mid May (early May – early Jun)
Once the frost threat passes, move hardened-off warm-season transplants into the garden (Iowa State University Extension). Northern gardens run later than southern ones — let your local frost date, not the calendar, make the call.
Source: Iowa State University Extension
Prune spring-flowering shrubs right after bloom
typically late May (mid May – mid Jun)
Shrubs that bloom early on last year's growth — lilac, forsythia and kin — should be pruned immediately after they finish blooming (University of Minnesota Extension). Prune them in winter and you cut off the flower buds. Typical window: a few weeks after the last frost, as their bloom fades — go by the shrub, not the calendar.
What to plant in May
Planting windows timed from the zone's typical frost dates, from CSU Extension and UGA Extension guides. Open a plant for how to plant it.
Beettypically early May (late Apr – mid May)
Planting window for Beet (Beta vulgaris). Semi-hardy: sow 0–2 weeks before the last frost once soil is at least 40°F, ¾–1 in. deep; thin to 4–6 in.
Source: CSU Extension
Carrottypically early May (late Apr – mid May)
Planting window for Carrot (Daucus carota subsp. sativus). Semi-hardy: sow 0–2 weeks before the last frost in soil of at least 40°F, ¼ in. deep; thin to 2–3 in.
Source: CSU Extension
Cauliflowertypically early May (late Apr – mid May)
Planting window for Cauliflower (Brassica oleracea var. botrytis). Semi-hardy cole crop: transplants started indoors 5–7 weeks ahead go out 0–2 weeks before the last frost at 18 in.
Source: CSU Extension
Cherviltypically early May (late Apr – mid May)
Planting window for Chervil (Anthriscus cerefolium). Short-lived, cold-hardy annual in the carrot family (12–28 in. tall): seed in spring into moist, cool, well-drained soil — germination fails if soil is warm and dry; a partly shaded spot suits it. Not a houseplant.
Source: CSU Extension
Cilantro / Coriandertypically early May (late Apr – mid May)
Planting window for Cilantro / Coriander (Coriandrum sativum). Annual (1–3 ft) for full sun and moist-not-wet soil; sow in spring and again in fall — germination is unpredictable; stake once seed sets. Keep away from fennel.
Source: CSU Extension
Dilltypically early May (late Apr – mid May)
Planting window for Dill (Anethum graveolens). Annual (20–48 in.) for full sun and moist, medium-heavy, well-drained soil; direct seed — it resents transplanting; shelter from wind and stake above 18 in. Self-sows freely; cross-pollinates with fennel.
Source: CSU Extension
Fenneltypically early May (late Apr – mid May)
Planting window for Fennel (Foeniculum vulgare). Carrot-family herb, zones 4–10, full sun, moist but well-drained soil yet drought tolerant; attracts butterflies. Seed in spring or divide bulbs early spring. Keep away from bush beans, kohlrabi, tomatoes and dill.
Source: CSU Extension
Parsleytypically early May (late Apr – mid May)
Planting window for Parsley (Petroselinum crispum). Semi-hardy herb: sow 0–2 weeks before the last frost, ¼ in. deep, 4–6 in. apart; germination is slow (7–12 days).
Source: CSU Extension
Parsniptypically early May (late Apr – mid May)
Planting window for Parsnip (Pastinaca sativa). Semi-hardy: sow 0–2 weeks before the last frost, ½ in. deep, thin to 5–6 in.; very slow to germinate (15–25 days).
Source: CSU Extension
Potatotypically early May (late Apr – mid May)
Planting window for Potato (Solanum tuberosum). Semi-hardy: plant seed potatoes 0–2 weeks before the last frost, 4–6 in. deep and 12–15 in. apart; water regularly.
Source: CSU Extension
Swiss Chardtypically early May (late Apr – mid May)
Planting window for Swiss Chard (Beta vulgaris subsp. vulgaris). Semi-hardy: sow 0–2 weeks before the last frost, 1 in. deep, 7–9 in. apart; succession plant for continuous harvest.
Source: CSU Extension
Celerytypically early May (late Apr – late May)
Planting window for Celery (Apium graveolens). Tender: set transplants out around the last frost date, 6–8 in. apart; needs consistent moisture all season.
Source: CSU Extension
Pole Beantypically early May (late Apr – late May)
Planting window for Pole Bean (Phaseolus vulgaris). Warm-season: direct seed after the last frost, and again in midsummer for a fall crop, 1–1½ in. deep, 36 in. rows × 4–12 in.; trellis or poles.
Source: UGA Extension
Snap Beantypically early May (late Apr – late May)
Planting window for Snap Bean (Phaseolus vulgaris). Tender: direct seed around the last frost date once soil 6 in. deep reads 55°F, 1–1½ in. deep, 6 in. apart (or 4 × 12 in.).
Source: CSU Extension
Sweet Corntypically early May (late Apr – late May)
Planting window for Sweet Corn (Zea mays). Tender: direct seed around the last frost date, 1–1½ in. deep, 12 × 30 in. or 9 × 36 in.; succession plant for a longer harvest.
Source: CSU Extension
Sow Potato for a fall harvesttypically mid May (early May – late May)
Second-season sowing: for a fall crop, plant potato about 139 days before the first fall freeze — 125 days to maturity plus a two-week margin for slowing autumn growth. Semi-hardy: plant seed potatoes 0–2 weeks before the last frost, 4–6 in. deep and 12–15 in. apart; water regularly.
Source: CSU Extension
Sow Onion (dry bulb) for a fall harvesttypically mid May (early May – early Jun)
Second-season sowing: for a fall crop, plant onion (dry bulb) about 134 days before the first fall freeze — 120 days to maturity plus a two-week margin for slowing autumn growth. Set plants in late winter, or in fall for overwintering short-day types, 18–36 in. rows × 3–4 in.
Source: UGA Extension
Cantaloupetypically late May (mid May – early Jun)
Planting window for Cantaloupe (Cucumis melo). Very tender vine crop: direct seed (preferred) or 2–3-week transplants 2+ weeks after the last frost in 60°F soil, 1–1½ in. deep, 36–48 in. apart.
Source: CSU Extension
Cucumbertypically late May (mid May – early Jun)
Planting window for Cucumber (Cucumis sativus). Tender vine crop: seed (preferred — roots resent disturbance) or 2–3-week transplants after frost danger, 1 in. deep; 6 in. trellised or 24–36 in. untrellised.
Source: CSU Extension
Eggplanttypically late May (mid May – early Jun)
Planting window for Eggplant (Solanum melongena). Very tender: set transplants started indoors 6–9 weeks ahead 2+ weeks after the last frost, 18–24 in. apart; needs consistent warmth.
Source: CSU Extension
Lima Beantypically late May (mid May – early Jun)
Planting window for Lima Bean (Phaseolus lunatus). Very tender: direct seed 2+ weeks after the last frost once soil is 60°F, 1–1½ in. deep, 6–12 in. apart.
Source: CSU Extension
New Zealand Spinachtypically late May (mid May – early Jun)
Planting window for New Zealand Spinach (Tetragonia tetragonioides). Tender, heat-tolerant warm-season stand-in for spinach: seed or transplant after frost danger, 1 in. deep, 12–18 in. apart.
Source: CSU Extension
Okratypically late May (mid May – early Jun)
Planting window for Okra (Abelmoschus esculentus). Heat-loving: direct seed once soil is warm, 1 in. deep, 36 in. rows × 12 in.; a later sowing extends the harvest; pick pods young and often.
Source: UGA Extension
Peppertypically late May (mid May – early Jun)
Planting window for Pepper (Capsicum annuum). Very tender: transplants started 6–8 weeks ahead go out 2+ weeks after the last frost, 15–18 in. apart; shelter from cool winds.
Source: CSU Extension
Pumpkintypically late May (mid May – early Jun)
Planting window for Pumpkin (Cucurbita pepo / C. maxima). Very tender, long-season vine crop: direct seed 2+ weeks after the last frost, 1–1½ in. deep, 36–48 in. apart.
Source: CSU Extension
Rosemarytypically late May (mid May – early Jun)
Planting window for Rosemary (Salvia rosmarinus). Shrubby tender perennial, zones 7–11 (grown as an annual or in containers where colder); full sun, moist but well-drained soil, never overwatered. Light pruning after flowering; no fertilizer until after bloom.
Source: CSU Extension
Southern Pea (cowpea)typically late May (mid May – early Jun)
Planting window for Southern Pea (cowpea) (Vigna unguiculata). Heat-loving: direct seed after soil warms, through midsummer, 1–2 in. deep, 36 in. rows × 3–4 in.; blackeye, pinkeye, cream and crowder types.
Source: UGA Extension
Summer Squash (zucchini)typically late May (mid May – early Jun)
Planting window for Summer Squash (zucchini) (Cucurbita pepo). Tender vine crop: direct seed (preferred) or 2–3-week transplants after frost danger, 1–1½ in. deep, 36–48 in. apart.
Source: CSU Extension
Sweet Basiltypically late May (mid May – early Jun)
Planting window for Sweet Basil (Ocimum basilicum). Tender annual (12–24 in.), full sun, moist well-drained medium soil and wind protection; seed in spring once frost has passed, cuttings in summer; pinch to prevent flowering when growing for leaves.
Source: CSU Extension
Sweet Baytypically late May (mid May – early Jun)
Planting window for Sweet Bay (Laurus nobilis). Evergreen laurel hardy only from zone 8 (10–60 ft in the ground, usually grown in a container where colder and wintered indoors under 50°F nights); full sun, moist well-drained soil, slightly drought tolerant; prune to shape in summer.
Source: CSU Extension
Sweet Marjoramtypically late May (mid May – early Jun)
Planting window for Sweet Marjoram (Origanum majorana). Tender perennial treated as an annual outside zones 9–10 (12–40 in.); full sun and slightly alkaline, well-drained soil; seed in spring, cuttings spring to early summer; cut back after flowering; do not overwater.
Source: CSU Extension
Tomatotypically late May (mid May – early Jun)
Planting window for Tomato (Solanum lycopersicum). Very tender: set hardened-off transplants (started 5–7 weeks ahead) 2+ weeks after the last frost, 24 in. apart trellised.
Source: CSU Extension
Watermelontypically late May (mid May – early Jun)
Planting window for Watermelon (Citrullus lanatus). Very tender vine crop: direct seed (preferred) or 2–3-week transplants 2+ weeks after the last frost, 1–1½ in. deep, 36–48 in. apart.
Source: CSU Extension
Winter Squashtypically late May (mid May – early Jun)
Planting window for Winter Squash (Cucurbita maxima / C. moschata). Very tender vine crop: direct seed (preferred) or 2–3-week transplants 2+ weeks after the last frost, 1–1½ in. deep, 36–48 in. apart.
Source: CSU Extension
Sweet Potatotypically late May (mid May – mid Jun)
Planting window for Sweet Potato (Ipomoea batatas). Heat-loving: set slips after soil is thoroughly warm, 36 in. rows × 12 in.; long season, harvest before frost.
Source: UGA Extension
June
What to plant in June
Planting windows timed from the zone's typical frost dates, from CSU Extension and UGA Extension guides. Open a plant for how to plant it.
Sow Cabbage for a fall harvesttypically late Jun (early Jun – early Jul)
Second-season sowing: for a fall crop, plant cabbage about 99 days before the first fall freeze — 85 days to maturity plus a two-week margin for slowing autumn growth. Hardy cole crop: transplants 5–7 weeks old go out 2–4 weeks before the last frost at 18 in. spacing; direct seed in midsummer for fall harvest.
Source: CSU Extension
Sow Collards for a fall harvesttypically late Jun (early Jun – early Jul)
Second-season sowing: for a fall crop, plant collards about 99 days before the first fall freeze — 85 days to maturity plus a two-week margin for slowing autumn growth. Hardy Southern green: sow or transplant in late winter and again in late summer for fall, ½ in. deep, 36 in. rows × 8–16 in.
Source: UGA Extension
July
Midsummer lawn watering — deep, not daily
typically mid Jul (early Jul – late Jul)
Most lawns need about 1 to 1½ inches of water a week in summer heat — in one session, or two spaced 3 or 4 days apart, early morning (Iowa State University Extension). Avoid frequent, light applications, which promote shallow rooting. Letting bluegrass go dormant is also fine: it tolerates four to six weeks dormant without significant damage.
Source: Iowa State University Extension
What to plant in July
Planting windows timed from the zone's typical frost dates, from CSU Extension and UGA Extension guides. Open a plant for how to plant it.
Sow Carrot for a fall harvesttypically early Jul (late Jun – late Jul)
Second-season sowing: for a fall crop, plant carrot about 84 days before the first fall freeze — 70 days to maturity plus a two-week margin for slowing autumn growth. Semi-hardy: sow 0–2 weeks before the last frost in soil of at least 40°F, ¼ in. deep; thin to 2–3 in.
Source: CSU Extension
Sow Cauliflower for a fall harvesttypically early Jul (late Jun – late Jul)
Second-season sowing: for a fall crop, plant cauliflower about 84 days before the first fall freeze — 70 days to maturity plus a two-week margin for slowing autumn growth. Semi-hardy cole crop: transplants started indoors 5–7 weeks ahead go out 0–2 weeks before the last frost at 18 in.
Source: CSU Extension
Sow Kale for a fall harvesttypically early Jul (late Jun – late Jul)
Second-season sowing: for a fall crop, plant kale about 84 days before the first fall freeze — 70 days to maturity plus a two-week margin for slowing autumn growth. Hardy green: sow in late winter and again in late summer for fall, ½ in. deep, 36 in. rows × 8–16 in.; sweeter after frost.
Source: UGA Extension
Sow Parsley for a fall harvesttypically early Jul (late Jun – late Jul)
Second-season sowing: for a fall crop, plant parsley about 84 days before the first fall freeze — 70 days to maturity plus a two-week margin for slowing autumn growth. Semi-hardy herb: sow 0–2 weeks before the last frost, ¼ in. deep, 4–6 in. apart; germination is slow (7–12 days).
Source: CSU Extension
Sow Parsnip for a fall harvesttypically early Jul (late Jun – late Jul)
Second-season sowing: for a fall crop, plant parsnip about 84 days before the first fall freeze — 70 days to maturity plus a two-week margin for slowing autumn growth. Semi-hardy: sow 0–2 weeks before the last frost, ½ in. deep, thin to 5–6 in.; very slow to germinate (15–25 days).
Source: CSU Extension
Sow Snap / Snow Pea (edible pod) for a fall harvesttypically early Jul (late Jun – late Jul)
Second-season sowing: for a fall crop, plant snap / snow pea (edible pod) about 84 days before the first fall freeze — 70 days to maturity plus a two-week margin for slowing autumn growth. Hardy: direct seed in late winter, 1–2 in. deep, 36 in. rows × 2 in.; trellis taller types.
Source: UGA Extension
Sow Broccoli for a fall harvesttypically mid Jul (late Jun – late Jul)
Second-season sowing: for a fall crop, plant broccoli about 79 days before the first fall freeze — 65 days to maturity plus a two-week margin for slowing autumn growth. Hardy cool-season cole crop: set out transplants (started 5–7 weeks ahead) 2–4 weeks before the last frost; space 18 in. Direct seed in midsummer for a fall crop.
Source: CSU Extension
Sow Garden Peas for a fall harvesttypically mid Jul (late Jun – late Jul)
Second-season sowing: for a fall crop, plant garden peas about 79 days before the first fall freeze — 65 days to maturity plus a two-week margin for slowing autumn growth. Hardy: direct seed 2–4 weeks before the last frost, 1 in. deep, 4–6 in. apart (or 3 in. in 8-in. rows); replant in midsummer for a fall crop.
Source: CSU Extension
Sow Beet for a fall harvesttypically mid Jul (early Jul – late Jul)
Second-season sowing: for a fall crop, plant beet about 74 days before the first fall freeze — 60 days to maturity plus a two-week margin for slowing autumn growth. Semi-hardy: sow 0–2 weeks before the last frost once soil is at least 40°F, ¾–1 in. deep; thin to 4–6 in.
Source: CSU Extension
Sow Green Onion (bunching) for a fall harvesttypically mid Jul (early Jul – late Jul)
Second-season sowing: for a fall crop, plant green onion (bunching) about 74 days before the first fall freeze — 60 days to maturity plus a two-week margin for slowing autumn growth. Hardy: sow seed (or sets) 2–4 weeks before the last frost, ¼ in. deep, 2–3 in. apart.
Source: CSU Extension
Sow Leaf Lettuce for a fall harvesttypically mid Jul (early Jul – late Jul)
Second-season sowing: for a fall crop, plant leaf lettuce about 74 days before the first fall freeze — 60 days to maturity plus a two-week margin for slowing autumn growth. Hardy: sow 2–4 weeks before the last frost, ¼ in. deep, thin to 7–9 in.; succession plant every 2 weeks for a steady supply.
Source: CSU Extension
Sow Swiss Chard for a fall harvesttypically mid Jul (early Jul – late Jul)
Second-season sowing: for a fall crop, plant swiss chard about 74 days before the first fall freeze — 60 days to maturity plus a two-week margin for slowing autumn growth. Semi-hardy: sow 0–2 weeks before the last frost, 1 in. deep, 7–9 in. apart; succession plant for continuous harvest.
Source: CSU Extension
Sow Kohlrabi for a fall harvesttypically late Jul (mid Jul – early Aug)
Second-season sowing: for a fall crop, plant kohlrabi about 64 days before the first fall freeze — 50 days to maturity plus a two-week margin for slowing autumn growth. Hardy cool-season crop: seed or transplant 2–4 weeks before the last frost, ½ in. deep, 7–9 in. apart.
Source: CSU Extension
Sow Mustard Greens for a fall harvesttypically late Jul (mid Jul – early Aug)
Second-season sowing: for a fall crop, plant mustard greens about 64 days before the first fall freeze — 50 days to maturity plus a two-week margin for slowing autumn growth. Fast hardy green: sow in late winter and again in late summer for fall, ½ in. deep, 18–36 in. rows × 2 in.
Source: UGA Extension
Sow Turnip for a fall harvesttypically late Jul (mid Jul – early Aug)
Second-season sowing: for a fall crop, plant turnip about 64 days before the first fall freeze — 50 days to maturity plus a two-week margin for slowing autumn growth. Hardy cool-season root crop: sow 2–4 weeks before the last frost, ½ in. deep, thin to 4–6 in.
Source: CSU Extension
August
Seed or overseed a cool-season lawn
typically mid Aug (early Aug – late Aug)
Late summer — mid-August to mid-September in Iowa — is the best time to establish a cool-season lawn from seed (Iowa State University Extension): seed germinates quickly in warm soil, warm days and cool nights push growth, and fewer weed seeds germinate in fall.
Source: Iowa State University Extension
What to plant in August
Planting windows timed from the zone's typical frost dates, from CSU Extension guides. Open a plant for how to plant it.
Sow Spinach for a fall harvesttypically early Aug (late Jul – mid Aug)
Second-season sowing: for a fall crop, plant spinach about 54 days before the first fall freeze — 40 days to maturity plus a two-week margin for slowing autumn growth. Hardy: sow 2–4 weeks before the last frost, ½ in. deep, 4–6 in. apart; replant in midsummer for fall harvest.
Source: CSU Extension
Sow Radish for a fall harvesttypically mid Aug (early Aug – late Aug)
Second-season sowing: for a fall crop, plant radish about 44 days before the first fall freeze — 30 days to maturity plus a two-week margin for slowing autumn growth. Hardy and fast: sow 2–4 weeks before the last frost, ½ in. deep, 2–3 in. apart; succession plant for continuous harvest.
Source: CSU Extension
September
Refresh pine straw before the first freeze
typically mid Sep (early Sep – late Sep)
Top beds back up to a 2–3 inch layer before the first freeze so soil moisture and temperature stay even through winter. Keep mulch 2–3 inches away from woody stems to prevent decay and rodent damage during the winter.
Source: Clemson Cooperative Extension (HGIC)· How to apply pine straw · How much you need
Blow out the sprinkler system before freezing weather
typically late Sep (early Sep – early Oct)
Water left in pipes, valves, and heads expands when it freezes and breaks them, so blow the system out with compressed air before hard freezes arrive. Use 40–80 psi (80 max for rigid PVC, 50 for poly pipe), never blow out a PVB or RP backflow preventer, and leave its valves half open for the winter.
Source: CSU Extension
Plant garlic
typically late Sep (mid Sep – mid Oct)
Plant garlic cloves in fall as the soil cools — in Iowa that's October (Iowa State University Extension) — 1 to 1.5 inches deep and 3 to 5 inches apart in well-drained, fertile soil. Use garden-center or mail-order seed garlic, not grocery cloves, and mulch fall plantings with a 4- to 6-inch layer of weed-seed-free straw against winter injury.
Source: Iowa State University Extension
October
Make the final fall nitrogen application
typically early Oct (late Sep – mid Oct)
Make the season's last nitrogen application while the grass is still green and at least two to three weeks before the ground begins to freeze — about 1 lb of nitrogen per 1,000 sq ft for bluegrass and ryegrass. Fine fescue does not need a fall application.
Source: CSU Extension
Plant tulips, daffodils and other spring bulbs
typically early Oct (late Sep – mid Oct)
Plant spring-flowering bulbs once the soil has cooled — October in Iowa (Iowa State University Extension) — so they root well before the ground freezes. Planted too early, in warm September soil, foliage can emerge in fall; if the ground isn't frozen you can still plant as late as early winter.
Source: Iowa State University Extension
Keep watering new trees and fall plantings
typically mid Oct (early Oct – early Nov)
Newly planted trees are most susceptible to winter drought injury (CSU 7.211). From October into winter, keep watering new trees, shrubs, perennials and fall-seeded lawns during dry spells — water midday, when air and soil are above 40°F with no snow cover.
Source: CSU Extension
Mound pine straw over tender perennials for winter
typically late Oct (early Oct – early Nov)
Once plants are fully dormant but before the ground freezes, loosely mound 6–18 inches of pine straw over tender perennials and new plantings — deeper for larger plants. Applying it too soon can keep plants from going fully dormant. Pull it back in early spring before growth resumes.
Source: Iowa State University Extension and Outreach· How to apply pine straw · How much you need
November
Early-winter watering check
typically late Nov (mid Nov – mid Dec)
In dry winters, water trees, shrubs and vulnerable plantings about once or twice a month from October through March (CSU 7.211). Water only when air and soil temperatures are above 40°F with no snow cover, at midday so it soaks in before nighttime freezing. Shallow-rooted woody plants and evergreens benefit most.
Source: CSU Extension
Plants for Zone 4
See the plants university extension guides recommend for your area, with planting windows timed to your frost dates. Enter your ZIP to narrow them to your region.
Browse Zone 4 plants