Transplants · heat mats · 1020 trays · not a kit

How to start transplants in a high tunnel: heat mats, 1020 trays, soil blocks, lights, and damping-off (sourced)

Growers search high tunnel seed starting, heat mat thermostat, 1020 tray, 72-cell and 128-cell plugs, soil blocker, humidity dome, and damping-off when the house is up and the spring crop is still a tray. This page is the transplant-bench sibling — how a germination chamber or mat differs from house heat, which 1020 cell counts Delaware and USU actually print, why a hoop house is a hardening space, and why condensation on the film is a damping-off sentence. House heaters stay on how to heat a high tunnel. Sensors stay on high-tunnel temperature monitoring. Tomato season stays on high-tunnel tomatoes. Winter lettuce calendars stay on high-tunnel winter lettuce. Direct-seed tools stay on high-tunnel bed-prep tools. It is not a commercially manufactured high-tunnel kit and not a USDA payment schedule.

Quotes copied 27 October 2026, about 04:00 UTC from University of Delaware Weekly Crop Update (Ernest, 4 April 2024), USU tomato-pepper and general transplant pages, K-State MF3126, UConn damping-off (July 2024 revision), UMass Wick/Dicklow (updated 16 June 2026), Johnny's soil- blocking guide (vendor), plus the High Tunnel System Initiative FAQ and the Pennsylvania seasonal high tunnel page. Featured Amazon prices copied the same night. A missing featured price stays an em dash. Ratings are not copied. Vendor 1020 block counts stay labeled vendor. This page does not invent a USDA dollar, a PPFD table, or a tool price.

Kit index: commercially manufactured kits. Replacement-parts directory: high-tunnel replacement parts. House heat: how to heat a high tunnel. Thermometers: temperature monitoring. Tomatoes: high-tunnel tomatoes. Winter lettuce: winter lettuce. Bed prep / seeders: bed-prep tools. Harvest: harvest / wash-pack. County inspection: EQIP checklist. What the program will not pay for: EQIP will not pay for. Affiliate method: about / disclosure.

A tunnel can harden. A chamber germinates.

K-State puts the hoop house on the hardening side. Delaware puts the mat and the chamber on the first 36–48 hours. USU still wants a heated greenhouse for quality plants. Those are three jobs. Do not swap them.

A four-season high tunnel, or hoop house, also works well as an unheated area for “hardening” transplants and as a growing space when heated. A cold frame or hoop house is an ideal environment for hardening transplants because it provides exposure to cool nights, high light, and some wind.

Source: K-State Research and Extension — MF3126 Growing Growers: Growing Your Own Vegetable Transplants (opened 27 October 2026). Transplant production Vegetable transplant production begins 60 to 90 days before planting. House propane and frost cloth stay on how to heat a high tunnel.

To decrease transplant production time and increase germination uniformity, place transplant trays in a germination chamber or on thermostatically controlled heat mats for the first 48-36 hours after seeding. Trays should be removed from the germination chamber or heat mats turned down to the optimal day temperature as soon as the root emerges from the seed and before the seedlings emerge. Continuous high temperatures will produce leggy transplants.

Source: University of Delaware Weekly Crop Update — Emmalea Ernest, Times and Temperatures for Vegetable Transplant Production (4 April 2024; opened 27 October 2026). Adapted from Mid-Atlantic Commercial Vegetable Production Recommendations Table A-4. USU chamber rule: A germination chamber will better control heat when floor or bench heat is not available. Flats, trays, or pots are seeded, watered, and then stacked in the chamber for germination. When using this method, be sure to remove the trays from the chamber and unstack them before the seedlings emerge.

Heat the media. Then turn the mat down.

Bottom heat is a germination tool. Leaving it on after the root emerges is how Delaware gets leggy plants. Featured Amazon tonight: a 17 W Jump Start mat and an Inkbird plug-in thermostat.

Optimum germination occurs at 86 °F, and the use of heating mats will increase speed of germination and the percentage of seedlings that emerge. Optimal temperatures for plant growth are 75 °F during the day and 65 °F at night.

Source: USU Extension — Transplant Production (tomato, pepper, eggplant; opened 27 October 2026). Tomato / pepper / eggplant page. USU also warns: Research has shown that germinating the seedlings at higher-than-recommended temperatures for too long results in etiolated (elongated) hypocotyls (stem under the seed leaves). UConn bottom heat: Germinate seed under conditions that will ensure rapid emergence, such as with the use of bottom heat (70-75˚F). Media below 68°F before germ: Low media temperatures (below 68˚F) before seeds germinate can also promote damping off.

Use heating mats or some other type of germination chamber to hasten germination and warm the soil environment.

Source: K-State Research and Extension — MF3126 Growing Growers: Growing Your Own Vegetable Transplants (opened 27 October 2026). A 17 W mat is not a 30×96 heater. Callahan's house-heat notes stay on the heating page.

1020 flats. 72-cell and 128-cell are crop lists.

Delaware printed the tray column. USU printed 50–72 for tomato and pepper. K-State said high-tunnel growers may want a larger plant. Johnny's soil blockers fill a 1020 with 72 or 128 cubes — vendor counts.

Tomato — 70-80 °F germ; 65-75 day; 60 night; 5-6 weeks; 50, 72, 128. Pepper — 80-90 °F germ; 70-75 day; 60 night; 7-9 weeks; 72, 128. Lettuce — 60-70 °F germ; 60-65 day; 40 night; 4-6 weeks; 96, 128, 200.

Source: University of Delaware Weekly Crop Update — Emmalea Ernest, Times and Temperatures for Vegetable Transplant Production (4 April 2024; opened 27 October 2026). Generally, you should use the smallest cell size that you can successfully establish in the field to reduce costs associated with growing media and greenhouse time and space. USU: If starting your own transplants, sow seeds into plastic plug trays with 50-72 cells per tray filled with a good soilless mix. Generally, transplants grown in larger cells (50s, 72s) produce earlier yields. Cell size does not affect total yield when growing seasons are long. Weeks: Allow 8 to 10 (pepper and eggplant) or 6 to 8 (tomato) weeks for growth of transplants depending on greenhouse temperatures.

For vegetable production, propagation trays with 48, 50, or 72 cells are typical because they are made from single sheet and easy to manage during large scale planting. On the other hand, high tunnel growers may prefer larger transplants that provide an early growth advantage over smaller transplants.

Source: K-State Research and Extension — MF3126 Growing Growers: Growing Your Own Vegetable Transplants (opened 27 October 2026). Johnny's (vendor): Johnny’s 12-Cell Handheld Soil Blocker: creates twelve 1 1/2” x 1 1/2” x 2” deep cubes, with dibbles. This blocker produces 72 cells per 1020 tray (6 compressions of 12). Johnny's 32-Cell Handheld Soil Blocker: creates 32 1" x 1 1 ⁄ 8 " x 1 1 ⁄ 2 " cubes with dibbles. This blocker produces 128 cells per 1020 tray (4 compressions of 32). Do not treat those as a land-grant tray mandate. Johnny's Selected Seeds — Soil Blockers, Soil Blocking Recipes + How to Soil Block (vendor page opened 27 October 2026).

Soil blocks air-prune. Plastic cells hold a mix.

USU prints an organic soil-blocking mix next to a standard peat-perlite tray mix. Johnny's (vendor) names air pruning. Featured Amazon tonight is a Ladbrooke Mini 4 — four 2-inch blocks — not Johnny's 12-cell or 32-cell SKU.

As seedlings grow in soil blocks, their roots reach the edges of the soil block and are “air pruned.”

Source: Johnny's Selected Seeds — Soil Blockers, Soil Blocking Recipes + How to Soil Block (vendor page opened 27 October 2026). Vendor copy. USU still wants soilless plug trays for tomato and pepper unless you choose a blocking mix. Direct-seed Jang / EarthWay tools stay on bed-prep tools.

Lights for early season. Sun after true leaves.

USU fluorescent numbers are a winter-start sentence. K-State says fluorescent is not enough after true leaves. A bright tunnel is sunlight. Weathered film is Delaware's low-light caveat.

Supplemental light may be necessary when growing transplants in the winter and early spring. Cool white fluorescent lights positioned 2 to 3 inches above the plants for 14 to 16 hours per day will ensure large and healthy seedlings.

Source: USU Extension — Transplant Production (tomato, pepper, eggplant; opened 27 October 2026). UD: Low light conditions (caused by cloudy weather or weathered greenhouse film) will slow transplant growth. K-State after true leaves: Once seedlings are established (either transplanted or direct-sown) and start forming new “true” leaves, they must have sunlight. Fluorescent lights will not provide enough light for proper growth. Do not average 2–3 inches with a vendor 3–6-inch hang height.

Harden 7–10 days. Watch the night number.

The hoop house is K-State's hardening room. USU printed the temperature floors. Biennials are water-hardened only.

Generally, impose hardening treatments about 7 to 10 days before field planting, such as: Reduce water provided to the plant. Lower the growing temperatures. Limit fertilizer amount. When hardening vine crops, tomatoes, peppers, or eggplants, do not lower temperature more than 5 °F below the recommended minimum growing temperatures. Exposing warm season vegetables to low temperatures (<45 °F) can cause chilling injury, which delays growth after transplanting. Biennial vegetables (cabbage, onion, endive, chard, or celery) should only be water-hardened, as cold treatments may induce vernalization and promote premature flowering.

Source: USU Extension — Transplant Production (general vegetable guide; opened 27 October 2026). Tomato / pepper daily cool: Condition or “harden off” transplants for a short time each day by exposing them to cool temperatures (60 °F to 65°F for eggplant and pepper, and 50 °F to 60 °F for tomato), starting one week before transplanting. K-State: The plant should be introduced to these variables gradually over 7 to 10 days to make sure it is ready for field conditions. Nights below 60 o F decrease growth of warm-season crops. Water morning so leaves dry: Keep the soil mix moist but not wet. Water in the morning when possible. This allows the leaves to dry before night and reduces disease.

Condensation drips. Damping-off follows.

A high tunnel at night is a wet ceiling. UConn wrote the drip sentence. UMass wrote the floor sentence. K-State wrote the dome-off sentence. New soilless mix. Flats off the dirt.

Excessive overhead misting or condensation dripping from greenhouse coverings to the growing media promotes damping-off. Keep greenhouse temperatures warm with low humidity. Condensation on the plastic causes drips which can then lead excessive moisture and damping-off. Overcrowded seed flats, which increases moisture and humidity levels around young seedlings, promote damping-off diseases.

Source: UConn Extension IPM — P.S. Mercure / Leanne Pundt, Damping-off of Ornamental and Vegetable Seedlings (latest revision July 2024; opened 27 October 2026). Soilless: Use commercially available soilless potting media that are free of damping off fungi. Diseased plugs: Do not reuse plug trays with diseased plants. It is very difficult to remove all the organic matter in the small plug trays so that the commercial disinfectants can work.

Keep flats off of dirt floors. Hang up the hose ends. When damping-off occurs in a flat, discard the entire flat. Healthy appearing plants may carry contaminated soil and may develop root rot or blight at a later date. Use a soil-less medium.

Source: UMass Amherst — Robert L. Wick and M. Bess Dicklow, Damping-Off of Bedding Plants and Vegetables (updated 16 June 2026; opened 27 October 2026). USU used trays: Use new flats and liners for transplant production to avoid pathogens that cause damping-off and other diseases. If old trays or liners are used, they should be thoroughly cleaned. Dip them in 10% chlorine bleach several times, then cover with plastic to keep them wet overnight. That 10% bleach line is USU's. K-State dome: During germination, maintain high humidity by using a glass cover or plastic dome over the seedling tray. If growing in a greenhouse, it is critical to cover the plastic dome to prevent it from becoming too hot on sunny days. Reduce humidity to ambient levels (50 to 80%) and provide light once seedlings emerge from the soil to prevent damping-off.

Sourced Amazon seed-starting gear

Titles and featured one-time prices were copied from live amazon.com product pages 27 October 2026, about 04:00 UTC. No featured 128-cell tray tonight. Skipped: B01KTO6G5E — Bootstrap Farmer 72-cell 2-pack: live PDP, currently unavailable / no featured price.; B000HJB2YI — Hydrofarm Jump Start digital thermostat: Amazon 404 tonight.; B00004S7V1 — Older Ladbrooke Mini 4 URL: HTTP 404.; B07LD5F3PQ — Older Barrina T5 URL: HTTP 404.; B0CKQN9JLM — SOLIGT 1020 kit with light and mat: fetch timed out.

EQIP pays for the structure, not the bench

Heat mats, thermostats, 1020 trays, domes, soil blockers, grow lights, and nursery benches sit outside the High Tunnel System Initiative payment. Confirm with your NRCS district conservationist. Tunnel Spec does not invent a dollar.

Under the High Tunnel System Initiative, financial assistance is provided only for the structure itself. Electricity, venting systems, lighting, etc. can be installed providing the additions meets manufacturer’s designs and specifications. However, the grower is responsible for those costs.

Source: USDA NRCS High Tunnel System Initiative FAQ (Updated November 2024; Oregon-branded). That PDF names electricity, venting, and lighting as grower cost. It is silent on a heat-mat dollar.

Producers can install heating, ventilation, or electrical systems at their own expense.

Source: USDA NRCS Pennsylvania — Seasonal High Tunnel System for Crops. One state office page, not a national tray payment. More exclusions: what EQIP will not pay for.

Rules vary; call your county NRCS office.

FAQ

Can you start transplants inside a high tunnel?

K-State MF3126: a four-season high tunnel works as an unheated hardening space and as a growing space when heated; a hoop house is an ideal hardening environment (cool nights, high light, some wind). USU: high-quality transplants are almost always grown in heated greenhouses with managed media, temperature, fertilizer, water, and spacing. UD: germination chambers or thermostatically controlled heat mats for the first 36–48 hours, then turn the mat down. A high tunnel is not automatically a germination chamber. House heat stays on the heating page. EQIP pays for the structure, not mats, trays, lights, or benches.

What tray size — 1020, 72-cell, or 128-cell?

UD (adapting Mid-Atlantic Commercial Vegetable Recommendations): tomato 50 / 72 / 128; pepper 72 / 128; lettuce 96 / 128 / 200; brassicas 72; cucurbits 50 / 72. Use the smallest cell you can establish. USU: 50–72 cells for tomato/pepper/eggplant; larger cells (50s, 72s) produce earlier yields; cell size does not change total yield in a long season. K-State: 48 / 50 / 72 are typical; high-tunnel growers may prefer larger transplants. Johnny's (vendor): a 12-cell handheld blocker fills a 1020 with 72 cubes; a 32-cell fills it with 128. Do not average those systems into one Tunnel Spec tray.

How do heat mats, thermostats, and germination chambers work?

UD: mats or a chamber for 36–48 hours after seeding; set the thermostat to the crop’s optimum germination temperature; remove trays or turn mats down as soon as the root emerges and before the shoot emerges — continuous high temperatures make leggy plants. USU tomato/pepper: 86°F optimum germination; mats raise speed and percent emergence; then 75°F day / 65°F night. USU general: unstack a germination chamber before seedlings emerge; too-long high temperatures elongate hypocotyls. UConn: bottom heat 70–75°F; media below 68°F before germ favors damping-off. Those are their numbers. Do not leave a mat on all season.

Do you need grow lights inside a high tunnel?

USU tomato/pepper: supplemental light may be necessary in winter and early spring; cool-white fluorescent 2–3 inches above plants, 14–16 hours. UD: low light from cloudy weather or weathered film slows growth. K-State: after true leaves, fluorescent is not enough — sunlight, or metal halide / HPS / LED. A tunnel on a bright day is sunlight. Early-season starts under weathered film or on a north bench may still need a bar light. Do not invent a PPFD table or treat a 2-foot 8-pack as a house lighting design.

What is hardening off, and what about night temperature?

USU general: harden 7–10 days before planting — less water, lower temperature, less fertilizer; do not drop warm-season crops more than 5°F below the recommended night minimum; below 45°F can chill tomato/pepper/eggplant/vines; biennials (cabbage, onion, endive, chard, celery) should be water-hardened only. USU tomato/pepper: 50–60°F tomato and 60–65°F pepper/eggplant, one week, a short time each day. K-State: 7–10 days; hoop house for cool nights and wind; nights below 60°F slow warm-season growth. Water in the morning so leaves dry before night (USU).

How do you avoid damping-off and condensation drips?

UConn: condensation dripping from coverings onto media promotes damping-off; media below 68°F before germ; overcrowded flats; use soilless media; do not reuse diseased plug trays; bottom heat 70–75°F; keep the house warm with low humidity. UMass: soil-less medium; keep flats off dirt floors; hang hose ends; discard the entire flat if damping-off appears. USU: new flats, or 10% bleach overnight on used ones; water morning, moist not wet. K-State: vent the dome after emergence; drop humidity to 50–80% and give light. Those are sanitation and climate sentences, not a fungicide rate.

Does EQIP / NRCS practice 325 pay for heat mats, trays, or lights?

Tunnel Spec does not invent eligibility or dollars. The High Tunnel System Initiative FAQ (Updated November 2024) says financial assistance is provided only for the structure itself, and that electricity, venting systems, lighting, etc. can be installed if they meet manufacturer designs — the grower is responsible for those costs. The Pennsylvania seasonal high tunnel page says producers can install heating, ventilation, or electrical systems at their own expense. Heat mats, thermostats, 1020 trays, domes, soil blockers, grow lights, and benches sit with those grower costs. Confirm with your NRCS district conservationist. See what EQIP will not pay for.

Rules vary; call your county NRCS office. Tunnel Spec does not determine eligibility, payment rates, or inspection outcomes. Not a PPFD table and not a USDA dollar. As an Amazon Associate, we earn from qualifying purchases.