Autumn is upon us and it’s time to review your sedum roof maintenance. What worked well this year? What wasn’t so good? Did your roof perform the way you wanted it to?

In this article we’ll look at some common green roof maintenance issues and help you to address them. We’ll also give you a very short list of jobs to do this autumn.

Common Sedum Roof Questions

Why did I not see many flowers on my green roof this summer?

For your sedum roof to flower it needs to have enough of three things

  • Sunlight
  • Water
  • Plant Nutrients

Sedums need to spend at least half of the day in sunshine not shade. If your green roof is shaded by buildings or trees, it could be that the sedums are not seeing enough sun. Another sign of this is that some of the more shade tolerant species eg Sedum Album will dominate whilst the other species languish and disappear.

white flowers of sedum album on a living green roof

A happy, healthy sedum green roof will normally bloom between April and October depending on the species present

If the problem is with trees – see if you can trim some of the branches back. If buildings are casting too much shade there’s not a lot you can do other than keep your sedum roof well fed and consider introducing some shade tolerant flowering plants that don’t mind shallow growing medium or dry summers. 

Shade tolerant plants that will grow and flower in a shallow substrate include chives. If sedums won’t grow on part of your roof chives are a good substitute. Butterflies and bees love the purple flowers. But beware, they can be a bit invasive.

Why are there bald patches on my sedum roof?

The first thing to do is decide is what has caused the problem. If the substrate is mossy and damp – then you could have a problem with drainage. Sedums won’t survive if their feet are perpetually wet.

Maybe the roof has been walked on a little too often? Could the bare patches be footprints? Can you see a path? If the culprit is wildlife – then well done you! Your roof is doing it’s job. If people are to blame then perhaps you need to “have a word” to make sure it doesn’t happen again. If you need regular access to rooftop features, order yourself some turf laying boards and use them to spread your weight as you walk over the plants. Don’t leave them down though!

large sedum roof in poor condition because of underfeeding

Lack of spring maintenance has led to this sedum roof underperforming. It doens't look great right now but tidying up the pebble edges and giving it a good feed in the spring should improve its condition rapidly.

The usual reason for bald areas though is lack of food or water.  On a sloping roof make sure you feed at least twice a year and check on a monthly basis that all of the substrate is damp. Rainfall may not be enough to sustain the plants on a slope – supplement it with irrigation if needs be.

On a flat roof, make sure that plant feed is applied EVERY spring and that it’s applied evenly across the whole roof.

At this time of year there’s not much to be done about bald patches but make a note in your diary to feed the roof in February.

Why is my green roof red?

Sedum foliage will turn a red-brown colour when the plants feel stressed by drought, by cold or by lack of water. If your roof has been red all summer, it’s likely that the spring feed was insufficient. Consider giving a light feed in late February next year and then following up with a second feed in late April early May. Just to top up nutrient levels. Do not feed in autumn or winter. 

What do I do about weeds on my sedum roof?

These are inevitable, even on sedum roofs with shallow substrate. Simply pluck them out by hand. Ideally before they can set seed. Tree seedlings MUST be weeded out before they damage the waterproofing. 

autumn leaves blocking drainage outlet on sedum green roof

Something as simple as a blocked drainage outlet can cause enormous problems to the plants on a sedum roof.

Sedum Roof Maintenance Jobs for autumn

  • Look for physical damage and repair it immediately – things like missing substrate, broken fall restraints or worse – damage to the waterproofing.
  • Check that edgings are intact and safe from strong winds
  • Clear drainage outlets and gutters
  • Remove fallen leaves and other debris from the roof – they block light from the plants and will eventually kill them
  • Take out weeds and remove them from the roof
  • Order green roof feed ready for spring
  • Schedule a date for spring maintenance so you don’t forget to do it.

More articles on green roof maintenance

 Solving green roof problems

Can you walk on a sedum green roof?

 

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