Glass greenhouse
Credit: BC Greenhouses

Glass greenhouse

Roof vents allow hot summer air to escape.

If you have recently acquired a greenhouse or are a novice at operating one, here are some helpful tips.


* This is a top priority. Poor ventilation and excess humidity during cooler weather cause mould and fungi to grow rapidly. Automated solar-operated roof vents allow hot air and excess humidity to escape. Supplementary thermostatically controlled fans can be installed to move air more quickly.

Summer Cooling

* Shade cloth or a roll-up bamboo blind can help reduce temperatures on sunny days.

* Wetting the ceiling, shelves and floor of the greenhouse in mid afternoon helps reduce temperature and raise humidity.

* Grow a grapevine over part of the greenhouse roof: it will leaf out when the sun’s intensity is at its peak in summer and defoliate when it decreases.


* Water in the morning to prepare plants for the heat of the day.

* During cooler months, use warmer water from a pail, rather than cold tap water.


* Plate glass shelves allow light to pass through, are easy to clean and never rot.

* Supplementary shelving can be hung from the rafters using drapery cord.

Winter Heating

* Cut 5-cm-thick (2-in.) Styrofoam insulation panels to size and squeeze them in place between the studs and rafters on the north side of the greenhouse to reduce heat loss.

Starting Cuttings

* A good rooting medium for cuttings is equal parts peat, perlite and sharp sand.

* Place a sheet of newspaper over a flat of cuttings for the first few weeks; it allows the right amount of indirect sunlight and helps reduce moisture loss.

* Watch for cool temperatures and excess moisture, which will cause cuttings to die.


* Control ants – which encourage aphids – with an equal mix of borax and icing sugar.

* Smear a piece of yellow cardboard with Tanglefoot to help control whitefly.