All the Tek

Tek library / Fruiting

Martha tent

A wire shelf inside a zip-up greenhouse cover, with a humidifier on a timer.

humidifier
Plate 12 of 16Martha tent, drawn for All the Tek.

What it is

A Martha tent is a small wire-shelf greenhouse with a clear zip-up cover, set up as a fruiting room. A humidifier feeds it through a tube, a timer or humidistat switches the humidifier on and off, and the zip front is opened or a small fan run for fresh air.

It is a scaled-down version of a commercial fruiting room. Cornell’s guide keeps fruiting rooms at about 62 to 65 °F, keeps humidity above 85% for the first days of pinning and in the 80% range after that, and runs humidifiers on a humidistat or timer1. Above about 75 °F many species fruit less and give lower-quality mushrooms1.

We found no university publication that tests the Martha tent itself. The design numbers above are the fruiting conditions it is trying to hit.

What it suits

Any species you fruit from blocks or bags, at the scale of a dozen or more at once.

Species notes are on the species page; for the mushrooms themselves, see Ohio Gourmet Mushrooms.

Equipment

  • A wire shelving unit with a clear zip-up cover
  • An ultrasonic humidifier and tubing
  • A timer or humidistat
  • A small fan for air exchange, optional
  • A hygrometer and thermometer
  • Shop lights or LED strips1

Time to first harvest

Depends on the blocks; the tent adds no wait. The tent is where colonised blocks fruit. Incubation before that runs about 10 to 20 days for oyster on sawdust, about 21 days for most specialties and 42 to 84 days for shiitake1.

Contamination and other risks

  • Saturated air. Penn State advises against relative humidity of 95–100% because cobweb mould germinates fast in it2.
  • Wet caps that stay wet for hours, which favour bacterial blotch3.
  • Too little fresh air, which gives long stems and small caps1.

Steps, in overview

  1. Assemble. Build the shelf, put on the cover and run the humidifier tube into the bottom.
  2. Wire the controls. Put the humidifier on a timer or humidistat1.
  3. Light. Hang ordinary shop lights or LED strips nearby1.
  4. Load. Place blocks with space between them, cut for their species1.
  5. Adjust. Watch the mushrooms: long stems mean more fresh air, cracked caps mean more humidity.

Common mistakes

  • Running the humidifier constantly, so everything drips2.
  • Keeping the zip shut all day and starving the mushrooms of air1.
  • Putting the tent in a warm room above 75 °F1.

Safety

Keep plugs and power strips outside the tent and below nothing that drips.

A full tent of fruiting oysters puts a lot of spores into the room4; oyster spores have been linked to hypersensitivity pneumonitis in growers5. Ventilate the room as well as the tent.

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Sources

  1. Methods of Commercial Mushroom Cultivation in the Northeastern United States. Willie Crosby (Fungi Ally) and Steve Gabriel, Cornell Small Farms Program, 2019 (Northeast SARE). Extension publication, checked 26 October 2026.
  2. Basic IPM Practices for Organic Mushroom Farms: Fungal Diseases of Mushrooms. Gorgo-Gourovitch, Beyer and Pecchia, Penn State Extension, 2021. Extension publication, checked 26 October 2026.
  3. Bacterial Blotch Disease. David M. Beyer, Penn State Extension. Extension publication, checked 26 October 2026.
  4. D.I.Y. FunGuide: Grow Your Own Oyster Mushrooms at Home. Hameed, Cotter, Liao and Hsu, UF/IFAS Extension (EDIS SS662). Extension publication, checked 26 October 2026.
  5. Hypersensitivity pneumonitis associated with mushroom cultivation. Satoh and Yamada, Journal of Postgraduate Medicine, 2022. Research, checked 26 October 2026.