Greenhouse maintenance

General maintenance tips

• Put canes around plants that need support; such as cordon tomatoes and melons, and tie in emerging shoots.
• Prick out, pot on and pinch out plants as needed. Summer pruning and fruit thinning may be required with some plants, such as grape vines.
• Water regularly, making sure that the composts and soils don't dry out.
• Weed around plants and in the beds.
• Make sure that plants are fed as required.
• Put up shade nets in early summer to protect plants from scorching by direct overhead sunlight. Shading washes can also be sprayed onto the outside of the greenhouse and washed off in autumn.
• Avoid watering plants in the middle of the day during summer as this can scorch the leaves.
• Some plants prefer high humidity, so splash the floor with water (called 'damping down') each day in the summer or use a hand-held mist sprayer.
• Look out for pests and diseases and treat appropriately. Common pests in warm, humid conditions include aphids, red spider mite and mealy bug. Diseases include mildew and botrytis.

Humidity control

• Cold water straight from the tap can shock plant roots in summer. Therefore keep a watering can full of water inside the greenhouse during summer to ensure you have a supply of warmer water.
• Another way of raising humidity is to place a tray of water on the floor which will slowly evaporate into the air.
• To lower humidity, keep vents and windows open in the summer. This will help to keep plants cool and prevent scorching in the heat of the day.
• You may want to invest in automatic vents which open and close according to the temperature. Extractor fans are also useful.

The annual clean

• A regular clean will help maintain the structure of your greenhouse, particularly if the frame is made from wood and therefore prone to rotting. Dirty windows affect sunlight levels - less light can lead to seedlings becoming straggly.
• The ideal time for cleaning is just before spring sowing as this will remove over-wintering pests and diseases and the greenhouse is likely to be at its emptiest at this time of year.
• Try to choose a mild day as you will have to open the doors and vents to clean them thoroughly. You don't want icy winds damaging valuable specimens.

Exterior

• Clean the exterior of the greenhouse by washing the panes of glass with warm water and a sponge.
• Higher parts of the greenhouse can be reached by attaching a sponge to the end of a broom handle or a bamboo cane.
• Old plastic labels or a gentle jet wash attachment on the end of a hose are ideal for getting in under the window panel joints to remove the build up of dirt underneath.
• Clean on a moderately windy day and let the breezes dry out the greenhouse as it's washed.
• Once the panes of glass are dry, insulate the greenhouse with bubblewrap to protect any plants you are overwintering, and to encourage the greenhouse to heat up more rapidly in the spring.
• Check the panels for any broken or cracked glass. They should be replaced. If you are planning on doing the job yourself, then you should wear gloves and goggles.
• Wooden frames can be painted using a wood preservative, making sure that none of the solution touches the plants.

Interior

• When starting on the interior of the greenhouse, ensure that the electricity is turned off and all electrical equipment such as heaters and radios are unplugged.
• Clean the interior by removing all the containers, pots and shelving/staging.
• If some of the plants are slightly tender, then move them into another shed or greenhouse.
• Otherwise, wrap them in fleeces and try not to keep them outside for too long.
• If the temperature is cold outside, then you will just have to work around them in the greenhouse.
• Throw out old used growing bags, remove all the leaves that will have fallen from the plants, and sweep the floor to remove any dirt and spilled soil.
• Also, pick off any damaged or infected leaves and burn them.
• Throw out any dead and dying plants.
• Weed the plant beds.
• The paths and brick walls should also be scrubbed with clean water and disinfectant.
• Sterilise containers, staging, propagation benches and capillary matting - although replacing capillary matting each year is better.
• Also check that all ventilation panels and windows are operating properly and lighting and watering/irrigation systems are working.

Watch video

In this video Toby Buckland sets up a second-hand greenhouse.