Essential jobs to get your sedum roof ready for spring

Sedum green roofs are rarely green during the winter.  The plants naturally take on a rather lovely reddish-brown hue.  It’s the plants’ way of dealing with the stress of cold weather and lower light levels.

sedum roof transitioning from winter hues to spring colours

Spring time and this sedum roof has lost most of its winter redness, the plants are thriving and some are beginning to flower.

However, once the days start to get longer and warmer, the plants will start greening up and growing.  All being well, you should start to see flowers any time from late April onwards. Provided that the plants have everything they need.......

What do sedum plants need in spring?

Any living thing needs nutrition and air.  For plants, that means that their growing medium should contain both.

Good drainage allows roots to breath

Green roof substrate, which is what forms the basis of a sedum roof, is made up of different sized particles of minerals, sand and crushed rock.  Between the particles we find air and water.  If there’s too much water, there won’t be room for air.  Which is why sedums will not grow in soggy soil.

First job to do before spring gets here, and as soon as it’s safe to be standing on a roof, is to make sure the drainage is working properly.  Are all the gutters clear?  Are the drainage outlets free of dead leaves and debris?  I can’t stress enough how important that is.

sedum roof with grass infestationThis sedum roof in Stevenage is suffering from another of the consequences of poor drainage - grass infestation.  In this case, the sedum plants still look good but they are at risk of being starved of light and air by grass.  This roof has only 20mm of growing medium, shallow enought so that with good drainage the grass would quickly die through lack of water.

Sedum plants love daylight

Plants derive much of their energy and nutrition from sunlight.  The chemical process involved is called photosynthesis.  Photosynthesis can’t take place if the leaves are in the dark.  Without photosynthesis, a plant will die and you will have a baldy bit on your roof.

 

Make sure all the sedum plants on your green roof have plenty of access to sunlight.  That means removing any debris that may have blown onto the roof in winter.  Dead leaves, rubbish etc. 

Good nutrition = good results

In order to grow healthy foliage, flower and set seed, plants need quite a range of nutrients.  Humans need a balanced diet of carbohydrates, proteins, fats, vitamins and minerals for optimal health.   Plants need Nitrogen, Phosphorus, Potassium and quite a few micronutrients such as iron, sulphur and boron.

Plant nutrients are normally “made” by bacteria in the growing medium who recycle dead leaves, roots, bird poo and mini-beasts. Green roof substrate though is a man-made soil.  It doesn’t have much organic matter in it for bacteria to feed on.  That means, that if we want to sustain a nice dense covering of plants, we need to help fill the plants’ food store by adding green roof feed.

Green Roof Feed isn’t really taken up by plants until the growing medium warms up in spring time.  So there’s little point in throwing it about before mid-late february.  However, that doesn’t mean that you can’t buy some in advance so that you’re ready to feed as soon as the plants need it.

sedum roof with poor plant coverage as a result of not being fed

This sedum roof has not been fed for over 3 years.  As you can see, the species diversity has been lost, moss is taking over and the remaining sedum plants look small and weak

Enviromat Natural Green Roof Feed is exactly the right formula for sedum plants.  It’s got all the minerals they need. Plus, it’s relatively low in nitrogen.  Nitrogen is the nutrient used for growth.  If sedums on a roof grow too much too fast, they become soft and sappy.  That makes them vulnerable to wind-scorch, to damage from late frosts and to drying out in hot weather. These plants are dealing with difficult conditions.  They’re like athletes who can’t perform properly if they get too big.  So lawn food, houseplant food, potato food or whatever else you have in your shed, just isn’t right for your green roof.

Enviromat Natural Green Roof Feed is not available in garden centres.  To order yours, visit www.enviromat.co.uk or phone the office on 0333 456 4526 (7am – 5pm weekdays)

Your green roof job list for February:

  1. Clear debris from the roof
  2. Check drainage outlets and gutters are clear
  3. Order green roof feed

 

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