Spring is almost upon us and plants will soon be waking up. The plants on living green roofs will be hungry and in need of a little TLC. In this blog, we’re looking at how to care for your green roof in spring
Your green roof needs just a little bit of maintenance in early spring. Here are our suggestions for essential and optional green roof jobs.
- Clear debris
- Make sure drainage outlets are clear
- Remove unwanted plants
- Apply green roof feed
- Repair bare areas
- Add some more wildlife habitat
Clear debris from your green roof
Plants need sunlight in order to grow. If they are beneath dead leaves or rubbish, your green roof plants will be deprived of light and they will flounder and die.
If you have a wildflower roof, and you’ve not yet had the chance to remove spent vegetation, now is the time. Dead foliage, spend seed heads and anything else that’s desiccated and brown needs to be chopped down and removed from the roof. Give it a good shake to try to ensure that overwintering insects stay on the roof.
If you have a sedum roof and the leaves are a reddy-brown colour – they’re not dead. Leave them where they are and they’ll green up as the air temperature rises.
Make sure drainage outlets are clear
Your green roof is essentially a giant plant pot. Without drainage, the growing medium will become saturated. Excess water drives air out of the substrate and drowns the plants. You probably cleared all of your drainage outlets in autumn. But now that you’ve made the effort to climb onto the roof, it’s well worth checking them again.
Remove unwanted plants
I’m writing this in February so some herbaceous plants and seeds are still dormant. However, some unwanted plants are very easy to see right now. I’m talking tree seedlings in particular.
Tree seedlings can and will damage waterproofing over time. Every time you are on the roof and you spot one make a point to pull it out and dispose of it. I’m sure you don’t need me to remind you to be very careful when using garden tools on a green roof. There is only a finite amount of substrate (growing medium) up there and some buildups have very little to protect waterproofing against marauding garden spades – be careful not to pierce anything important.
Apply green roof feed
The sedum plants that are frequently used on green roofs are relatively economical when it comes to fertiliser. However, if you want a fabulous display of healthy plants this summer, a feed is essential.
We recommend this sedum fertiliser from Enviromat. Be sure to water it in – or better still, wait until rain is forecast and let Mother Nature water it in for you.
Repair bare areas
Bare or plant-free areas on a green roof do have some benefits to wildlife. Certain bee species like to nest in substrate and some creatures like to sun themselves in plant-free zones. However, if you feel there are too many bare patches on your green roof you have several options.
- Allow Mother Nature to colonise the space – it’s amazing what will grow where you least expect it to.
- Sow some seed. Wildflower seed is widely available but choose your species carefully. If your roof has a shallow substrate layer, your choices are limited.
- Use cuttings to repopulate the area. Sedums are easy to grow from cuttings. Wait until the danger of frost has passed and then break some small pieces off the plants growing elsewhere on the roof. Simply press the pieces onto the surface of the substrate and water keep them moist until they grow tiny roots. (normally 3-4 weeks depending on the weather)
- Plug plants are great on a deep substrate (100mm +) roof. Choose your species wisely and plant a good distance apart. You’ll find a good selection here. https://www.wildflowers.uk/
- Pregrown mats. For larger areas needing repair, pregrown mats such as Meadowmat or Enviromat are quick and easy to install. For shallow substrates on a sunny site, choose Enviromat sedum matting. For substrates of 10-15cm deep, Meadowmat is more biodiverse.
Add to the wildlife habitat
Green roofs have many benefits for us. I’m thinking insulation, rainwater management, noise amelioration etc. They also have a lot of potential benefits for wildlife. Why not add a log pile or an insect hotel to support minibeasts? If your roof is strong enough a small heap of sand makes a great place for mining bees to nest in and birds to bathe in.
If you do nothing else to your green roof this spring, please don’t neglect to feed it. You will benefit from more efficient insulation, cooler air and (depending on the species growing up there) a better floral display.