What To Plant In A Kansas Greenhouse Each Season

Kansas sits in USDA zones roughly 5 through 7, with wide internal variation between cold western plains and milder eastern counties. A greenhouse in Kansas is a powerful tool: it protects against winter freezes, allows earlier spring starts, extends harvests into fall, and — with careful environmental control — keeps crops thriving through hot, dry summers. This guide gives concrete, season-by-season planting recommendations, temperature and spacing targets, and practical management tips to maximize productivity year-round.

Winter (December-February): Grow Greens, Herbs, and Overwintered Crops

Winter in Kansas can be harsh. With a heated or well-insulated greenhouse you can grow a surprising variety of crops; with an unheated cold frame style greenhouse, choose cold-hardy plants only. The keys are insulating, maintaining temperatures, managing light, and reducing humidity spikes that encourage disease.

Best crops for winter

Leafy greens: spinach, winter lettuce mixes, mache (corn salad), arugula, mustard greens, and Swiss chard. These tolerate cool nights and prefer daytime temps of 50-65 F and nights above 35 F.
Herbs: parsley, cilantro, chives, thyme, and rosemary (rosemary prefers the warmer end and good light).
Microgreens: radish, broccoli, pea, sunflower — fast turnover, minimal space, high yields.
Overwintered alliums and brassicas: garlic planted in fall can be overwintered and finished in spring; onion sets and shallots can overwinter in milder microclimates.

Winter environmental targets and tips

Day temps: 56-65 F for most greens; 65-75 F for herbs like basil if heated.
Night temps: keep above 35 F for hardy greens; above 45 F for tender herbs.
Light: supplemental LED or fluorescent lighting is often necessary in December and January. Aim for 8-12 hours of good-quality light for lettuce; 12-16 hours for herbs like basil.
Airflow: use low-speed fans on timers to exchange air and reduce fungal disease risk.
Soil and containers: use a well-draining mix (example: 2 parts coco coir or peat, 1 part compost, 1 part perlite) with pH 6.0-6.8.

Practical winter schedule

Sow microgreens every 1-2 weeks for continuous harvest.
Start spinach and lettuce transplants in late December-January under lights for harvest through early spring.
Keep garlic planted in fall; mulch lightly if soil is exposed.
Rotate containers and sanitize trays between crops to prevent disease build-up.

Spring (March-May): Early Starts and Succession Planting

Spring is the busiest season in a Kansas greenhouse. Use the shelter to start warm-season plants early, transplant progressively, and plant cool-season crops for an extended spring harvest. Success depends on timing transplants to avoid shock when moving outside or to maintain greenhouse-only production.

What to sow and start in spring

Cold-tolerant starts in early March: broccoli, cabbage, cauliflower, kale, and early peas.
Warm-season transplants under protection (late March-April): tomatoes, peppers, eggplant, cucumbers, squash. Start seeds indoors at 6-8 weeks before intended transplant.
Salad mix succession: sow lettuce and arugula every 10-14 days for continuous pickings.
Herbs: basil, dill, and cilantro can be direct-sown or started now for spring and early summer harvest.

Planting details and transplanting

Tomato spacing: indeterminate varieties 18-24 inches on bench; 24-36 inches when grown to fruit outdoors or tall in greenhouse. Use cages or trellises.
Pepper spacing: 12-18 inches between plants.
Cucumber spacing: vines can be trellised vertically to save space; 12 inches between plants on trellis.
Harden off transplants gradually for 7-10 days if moving outdoors; if staying in the greenhouse, increase light intensity and airflow to prevent legginess.

Practical spring tips

Start a staggered schedule: sow small blocks of 10-20 seeds per crop every 2 weeks.
Apply a balanced starter fertilizer at transplant (e.g., 10-10-10 at labeled rates or compost tea for organic).
Watch for aphids and whiteflies early; introduce beneficial insects or use insecticidal soap when necessary.

Summer (June-August): Heat Management and High-Value Crops

Kansas summers can push greenhouses to extreme temperatures. The summer season is ideal for peak production of fruiting crops if you control heat, humidity, and light. Choose heat-tolerant varieties and adapt cultural practices.

Ideal summer crops

Tomatoes: heat-tolerant varieties like “Sungold” (cherry), “Celebrity,” and other indeterminate types suited to greenhouse trellising.
Peppers: bell and hot peppers perform well if high night temps are avoided.
Eggplant and okra: both tolerate heat and can be excellent greenhouse crops.
Cucumbers and melons: need pollination; trellis cucumbers, use hand pollination for melons or introduce pollinators.
Basil and other warm-weather herbs: harvest frequently to encourage bushy growth.

Temperature and humidity control

Ventilation: automated roof vents and side vents, plus circulating fans. Aim to keep daytime temps below 85 F for most fruiting crops; some varieties will tolerate higher but may set less fruit when nighttime temps exceed 70-75 F.
Shading: use 30-50% shade cloth during hottest months to reduce radiative heat.
Evaporative cooling: pad-and-fan systems or misting can reduce temps in dry conditions; be careful with humidity which can increase disease risk.
Night cooling: open vents at night when external air is cooler to flush heat.

Water and nutrition in summer

Irrigation: switch to more frequent, deep waterings or consider drip irrigation. Water early in the day to allow foliage to dry.
Fertility: fruiting crops need more potassium and phosphorus once set. Use a soluble feed with an N-P-K ratio adjusted toward 5-10-10 for fruiting stages, or follow crop-specific fertilizer schedules.

Pests and pollination

Common summer pests: spider mites, whiteflies, thrips, and aphids. Monitor weekly and use sticky traps, miticides, or biological controls (predatory mites, Encarsia) as needed.
Pollination: many greenhouse tomatoes are self-pollinating but respond to vibration (buzz pollination). Use an electric toothbrush or mechanical vibrator on trusses if pollinator access is limited. Cucumbers and melons need bees or hand pollination.

Fall (September-November): Second Crops and Storage Roots

Fall is an opportunity to plant another round of cool-season crops and start storage roots for winter. Cooler nights reduce disease pressure if humidity is managed and allow crisp lettuce and sweet root crops to develop flavor.

Fall crop choices

Brassicas: plant broccoli, kale, and cabbage in late August-September for fall harvest.
Lettuce and salad greens: succession plant through September; consider cold-tolerant varieties for late fall.
Root vegetables: carrots, beets, radishes, and turnips. Sow directly in containers or raised beds in the greenhouse.
Spinach and Asian greens: harvestable in 4-6 weeks; ideal for fall.
Overwintering: mulch hardy crops and use row cover inside the greenhouse to extend harvest into late November and December.

Fall management and harvest

Lower fertilizer rates as growth slows; heavier applications encourage tender growth that is susceptible to cold damage.
Reduce watering frequency and focus on even moisture for root crops.
Clean up spent summer crops to reduce pest and disease reservoirs. Sanitize benches and tools.

Preparing for winter

Plant cover crops (e.g., hairy vetch, winter rye) in beds that will rest over winter; chop and incorporate in early spring.
Top up compost and amend soil pH if needed (liming in fall can correct acidity).
Service heating systems and insulate pipes and vents before first freeze.

Year-Round Practices That Matter

Beyond seasonal crop choices, certain practices determine greenhouse success in Kansas regardless of the month.

Soil, containers, and fertility

Use well-draining mixes and rotate container-grown crops to avoid soil-borne disease buildup.
Maintain substrate pH 6.0-6.8 for most vegetables; adjust with lime or sulfur as needed.
Practice regular fertilization calibrated to crop stage. Monitor plant vigor and leaf color to avoid overfertilizing.

Integrated pest and disease management

Sanitation: remove old foliage, sanitize pots and tools, and prune to improve airflow.
Monitoring: use yellow sticky traps and weekly inspections to catch problems early.
Biological controls: maintain predator populations, introduce beneficials early in the season, and use selective treatments rather than broad-spectrum pesticides.

Succession and record-keeping

Keep a planting calendar: track sowing dates, germination rates, harvest windows, and problem notes so you refine timing each year.
Succession planting: aim to sow a new block every 1-3 weeks for high-turnover crops like salad mixes and microgreens.

Practical Takeaways

Winter: focus on greens, herbs, and microgreens; invest in supplemental lighting and insulation or plan for cold-hardy varieties.
Spring: start warm-season crops early and stagger sowings for continuous harvest; harden off transplants if moving outdoors.
Summer: prioritize heat control (ventilation, shading, evaporative cooling) and choose heat-tolerant, well-vented varieties; manage water and nutrients closely.
Fall: sow a second round of cool-season crops and root vegetables; prepare beds and systems for overwintering.
Year-round: maintain clean benches, well-draining media, balanced pH, pest monitoring, and a planting calendar to increase predictability and yields.

A Kansas greenhouse can produce fresh vegetables and herbs nearly year-round when you match crops to seasonal conditions and actively manage temperature, humidity, light, water, and fertility. Start with the crop lists above, experiment with a few trusted varieties, and refine timing and microclimate controls each year to maximize production and quality.