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Cleaning Your Greenhouse for the New Growing Season


It may not be the most fun job in the garden but cleaning out greenhouses is an important one before the new growing season begins as it greatly improves the growing environment for your plants. By removing the algae, moss and grime it lets in more light and helps control pests and diseases too. Yes, it’s not just plants that enjoy the protection of a greenhouse – pests and diseases love them too, avoiding the harsh weather and frosts that usually kill them off! 

Cleaning is essential to get rid of:

  • Slugs are probably the top pest for gardeners, they love to hibernate in hidden cracks, under old pots.
  • Aphids lay eggs before the winter becomes harsh, often on existing plants so removing old plant material is a must.  Aphids are one of the main ways that viruses are transmitted between plants.
  • Red spider mite love the hot dry conditions in greenhouses over summer and are ideal for them to multiply rapidly, reducing the crop of many plants.  The tiny red female insects can overwinter on greenhouse walls and pots so it is important to clean them out thoroughly.
  • Mealybug colonies resemble blobs of sticky cotton wool and are largely a greenhouse pest, sucking the sap from plants like aphids.  They can often be found under the rim of pots or similar places, which need to be cleaned thoroughly.
  • Botrytis is a fungal infection that can attack the foliage of plants left in damp conditions over winter.  It is important to fully ventilate the greenhouse and again remove all dead plant material to prevent this.
  • Mildew can survive on old plant material if we don't have a really cold winter.
  • Blight spores can easily spread to tomatoes and potatoes from plant debris left in the greenhouse or garden, so it must be removed and disposed of or burnt.


Late winter or early spring is usually the best time on a dry calm day.


  • Remove plants – a sheltered area with fleece protection is a suitable area to hold tender plants overwintering in the greenhouse while cleaning is carried out.
  • Remove everything else like benching, pots tools so you can reach every corner.
  • Brush or vacuum to remove all old debris and plant material for destruction or removal
  • Turn off the electricity before you start using water.
  • Scrub all benching, pots trays and any staging where your new plants will go.
  • Clean the structural parts with a disinfectant like Jeyes fluid or detergent.
  • Glazing material should also be washed inside and out, but for plastic materials test on a small inconspicuous area first to be sure the cleaning material does not damage the glazing.
  • Ease out dirt trapped between panes using a flexible scraper such as plastic plant label.
  • Replace broken parts such as vent controllers, glass and draught excluders.
  • Replenish soil if you grow your tomatoes in the same bed every year to make sure nutrient levels are maintained and disease risk reduced.

Posted by Charlie Groves

Charlie is the manager at Groves Nurseries.  He is the 6th generation of C.W. Groves to run the garden centre. 

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