Autumn Green Roof Maintenance

As September draws to a close, the leaves on the trees are just beginning to change colour and thoughts are turning towards putting the garden, the beehives and the green roof to bed for winter.

Time for final tidy up before winter sets in

This may be your last chance to climb up onto the roof before the winter weather makes it either impractical or downright dangerous.

Take the opportunity to remove any rubbish or debris.  Pull out any unwanted plants and take note of any major maintenance that might need to be scheduled in for spring.  For example, repairing fall restraint systems or replanting areas where the vegetation has become sparse.

The whole of a green roof buildup depends upon good drainage particularly if it is planted with succulants like these sedums.  When autumn leaves block drainage outlets it can result in unhealthy, dead or dying plants next spring.

If you have a wildflower green roof and haven’t got around to trimming off dead vegetation – now is the time to do it.  Trim everything down to a height of around 10cm (4 inches) but no lower.  At this length you won’t risk damaging the crown of perennial flowering plants AND you’ll leave enough cover for overwintering insects.

If you can, allow the hay to dry on the roof for a couple of days after cutting, then shake the seeds back onto the roof so that they can germinate next spring.

The two most important autumn maintenance tasks

The two most important tasks at this time of year are:

  1. Check that all drainage outlets and gutters are clear and that water can run off the roof with no problems
  2. Remove fallen leaves as quickly as possible – and definitely before they form a soggy mass on top of the plants.

Improving the biodiversity – optional, but good

If you have a relatively deep substrate layer on your roof, you could add in some new plug plants to increase biodiversity on the roof.

You might also like to plant some spring flowering bulbs.  Crocus and Muscari are particularly popular with bumblebees as they emerge from hibernation in the spring.

Adding an insect hotel before the first frosts arrive can be an enormous help to local wildlife….and, if you’re a business, it’s great for PR.  Insect hotels are widely available commercially or you can make your own.

Adding an insect hotel is a great way of increasing biodiversity without making a lot of work or impacting on the weight of the roof.  A simple log pile (provided the logs can’t roll off the roof and hurt anyone) is easy to create.  These logs have been drilled to make homes for solitary bees, but even without holes it can become a refuge for woodlice, spiders, overwintering ladybirds and a whole host of other plants, fungi and creatures.