There are some simple tasks that are important to do during the first two seasons so that the roof develops.
Green Roofs, like all gardens, require some amount of maintenance and, like gardens, the type of green roof you have will determine the amount of maintenance it needs. Intensive green roofs will require much more time and effort than extensive ones. So as there is no simple answer to the question of “how to maintain a green roof,” here are some general green roof maintenance tips.
General Green Roof Maintenance and Care
- Weed out unwanted plants. The soil comes with weeds and during the first season it is crucial to remove them to let the still junior plants establish. If you let the weeds run free then the plants we installed will be crowded out and you will be left with a roof full of dead weeks.
- Keep the drainage areas clear of plants. The border around the edge of the roof and the graveled areas around drain outlets and other roof penetrations should be kept clear of all plant life and vegetation. Plants growing too close to the drain will clog it up, which completely defeats the purpose of having a drain. Biannual weeding should suffice.
- Add compost biannually. Nutrient-rich compost should be added to the roof garden in spring and autumn. This provides plants with important nutrients and replenishes the soil.
- Weed out unwanted plants (again!). Being on a roof, seeds dropped by birds or carried by the wind inevitably find their way into your roof garden. Some of the seedlings are fine and can be left alone. Others, such as a budding oak tree, are not desirable. Most likely your roof could never support the weight of an oak, unless your building something like Derry and Toms in London. Monthly walk-throughs should be scheduled to monitor the types of vegetation growing on your roof. Unwanted plants, such as the aforementioned oak tree, should be replanted somewhere else, if possible. Get a group of friends together and do some guerilla gardening with those “unwanted” plants!
- Green roofs should be watered as little as possible. Water is extremely heavy and creates additional weight on the roof. For lightweight roofs with 4-6 inches of growing medium, desert-type plants are ideal because they require so little water. Experiment with plant types and, depending on how much rain you get, try to get to the point where you don’t have to water your roof at all. When it does become necessary to water your plants, err on the side of under watering. Also, if your roof garden is on a pitched roof, begin watering at the top of the roof to the water can trickle down through the plants at the bottom, which may not need any water at all.
- Watch out for pests and diseases. Keep an eye out for pests and diseases that may come to your roof garden. While green roofs are designed to attract insects and increase biodiversity, sometimes unwanted insects come along.
- Keep a detailed maintenance log/diary. Schedule when you’re going to do these checkups (and follow through!) and keep and detailed record of your findings. This will also help you see what plants do best in your roof’s environment.