Tips for Making the Most of Your Greenhouse

Are you getting everything that you hoped for out of your greenhouse? Roy Jonsson provides some helpful and handy tips on how you can make the most out of your greenhouse.

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Giving plants lots of breathing room is just one of the tips for better greenhouse gardening.

Ventilation – Poor ventilation and excess humidity during cooler weather cause mould and fungi to grow. Automated solar-operated roof vents allow hot air and excess humidity to escape. 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 and defoliate when it decreases.

Watering – 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 water directly from the tap.

Shelving – Plate glass shelves allow light to pass through, are easy to clean, do not allow soil to fall through onto plants below and never rot. Supplementary or temporary shelving can be hung from the rafters using drapery cord. Seedlings will benefit from the extra light.

Winter Heating – Cut 5-cm-thick (2-in.) Styrofoam insulation panels to size and place between the studs and rafters on the north side of the greenhouse to reduce heat loss. Two 110-volt electric lines on separate circuits with two heaters provide insurance if one heater burns out, the circuit breaker flips off or one heater is not sufficient to maintain the temperature.


Starting Cuttings – A good rooting medium for cuttings is equal parts peat, perlite and sharp sand (use sand-blasting sand). Place newspaper over cuttings for the first few weeks; it allows the right amount of indirect sunlight and helps reduce moisture loss. Cool temperatures and excess moisture will cause cuttings to turn black and die.

Pests – Control ants – which encourage aphids – with a mix of equal parts borax and icing sugar (out of reach of children and pets). Copper tape or wire pot cleaners deter slugs. Smear a 30-sq-cm (1-sq.-ft.) piece of cardboard with Tanglefoot to control whitefly.