If green roofs are “low maintenance” why do they need feeding?

When sedum green roofs first became fashionable in the UK, one of their USP's (unique selling points) was that they are "low maintenance".  Unfortunately, architects, developers, buildings' managers and maintenance folk interpreted "low maintenance" as "no maintenance"

Oh dear.

That was very wrong indeed.

• A sedum green roof IS drought tolerant --- so it rarely needs irrigation.  
• It is frost hardy----so doesn't need replacing after a bad winter.  
• It is low growing----so it doesn't need mowing, pruning, clipping or any of the other gardening jobs associated with herbacious perennials.
• It is quite thrifty when it comes to nutrients----so no need for frequent feeding as you would roses or tomatoes.

However, what is often overlooked with such an easy-going plant palette is that

• A sedum roof IS a living thing.  Which means that it DOES need an adequate supply of water and of the right nutrients.

Plants like this Sedum spurium need a booster feed in spring when they're growing on a roof

A living green roof is just like a huge container garden.  The plants growing in it have a finite amount of growing medium to get their roots into.  That means that there is a limited supply of nutrients for them to enjoy.

A green roof is equivalent to a large, shallow plant pot.
It needs similar care to your houseplants, raised beds and planted containers----but on an industrial (and more manageable) scale

At ground level, microscopic organisms in the soil pull nitrogen from the air and recycle dead plants and bugs to make a certain amount of plant food.  BUT, on a green roof, the substrate (growing medium) has been engineered to suit the needs of the building (light weight, free draining, with particles that are too big to wash off).  Green roof substrate is super, but the structure of it doesn't support soil microbes very well.

In addition, the harsh conditions on a roof put extra strain on the plants’ metabolism so, just like us when we’re working hard, green roof plants need the right food (and plenty of it!) to keep them in good health.

So, even self-sufficient plants like sedums need a little extra help if they are to thrive on a green roof and provide all the benefits you want them to.   ie insulation, cooling, wildlife habitat, good looks, showing off your "eco" credentials.

Here's what you need to keep your green roof in tip-top condition:

If you're still at the design stage.....choose your plants carefully and put plenty of thought into how your green roof will be maintained in the years to come.

This downloadable guide will help you.

If you already have a living green roof you will need some of this

Enviromat Natural Green Roof Feed has been specially developed to help you and your clients to get the best out of their green roofs.

It comes in a bucket – so it’s easy to carry up on to a roof.  The granular feed is easy to store and easy to apply.

YUK! a neglected sedum roof.  The hungry plants are too weak to hold the growing medium in place with their roots.  This roof looks ugly and its thermal performance is probably very poor.  It's not much use to wildlife either.

The formulation for this highly specialised feed is 7.9% Nitrogen, 2.97% Phosphorus, 2.47% Potassium and a whole host of essential trace elements that are needed to keep plants healthy in stressful conditions.  Enviromat Natural Green Roof Feed is a slow release feed, so on a healthy living roof, one feed a year is enough. 

Order your Green Roof Feed online or phone Q Lawns for a quote: 01842 828266

Electricity prices are rising so install a green roof

Today I arrived home from work to a seasonably chilly house and a husband who's mood could only be described as icy....our electricity supplier has announced an 11% price hike and he's not happy.

So what does that have to do with green roofs?

Newly installed green roof just begging to
have PV panels added

Well, to start with, a green roof is a fantastic insulator, keeping a building warmer in winter and cooler in summer so savings there on the heating bills.  I speak here for the lucky souls who happen to have "greenable" roofs on their homes.  Our house was build long before electricity, let alone green roofs.  It has a steeply pitched, tiled roof and although it's strong enough to support a green roof buildup, the installation and maintenance would be a nightmare.  So, until we retire into something more suitable, there'll be no living roof on our house to help save electricity; 

So what about generating our own power with solar panels?  My friend Ginny and her husband Chris swear by them.  Chris installed PV panels on their roof in Essex and when they moved to the depths of deepest Norfolk, the solar panels came too.  Apparently the solar panels provide all the hot water they need in the summer months so the only fuel they use between late spring and mid-autumn is for cooking, boiling the kettle for tea and maybe watching a bit of telly.

Again, hubby says PV panels won't suit the look of our pretty house, BUT, being a farm, we do have outbuildings and so maybe he'll be persuaded to put use at least one of them to generate our own power and show the electricity company what he thinks of their pricing structure.

If however, he installs PV panels in conjunction with a living green roof, we'll be quids in.   Solar panels work best when the temperature is below 30 degrees celcius. Of course on a roof, in summer, temperatures can rise a lot higher than 30 degrees, thus rendering the PV panel less efficient; but if it's a green roof, the cooling effect of the plants will keep the temperature more comfortable and the PV panels will be more efficient.  PS...remember to design the roof so that panels are not casting shade over the sedum plants..they don't enjoy being kept in the dark

Research in Germany compared  PV cells over a green roof  with cells over Bitumen roofs. In over 5 years of recording, the panels over the green roof showed an average 6% increase in yields

I like it! So here I am, in my kitchen, log-fired Rayburn creating a nice warm fug around me.  Laundry is drying on the clothes horse in front of the fire, kettle is whistling and I'm wondering how I can persuade my dearly beloved to leave the comfort of the armchair to climb on the roof, install some Enviromat and wire in some PV panels before electricity prices go up in December.  I'll let you know how I get on.

Oh....if you fancy a green roof yourself, drop me a line and I'll send you a copy of our "how to" guide and a phone number for our installation man in case you'd rather sit by the Rayburn and let someone else do the work (like me)