But if you hate the extra vegetation its weeding I’m afraid. On a shallow substrate roof you’ll often find that a period of drought will kill off the grass plants. They simply cannot tolerate dry conditions as well as sedums can.
This applies especially to tree seedlings. Never let them get established.
Moss loves damp shade. Is there a problem with drainage on the roof? Or have we just had such a wet winter that avoiding damp soil has been impossible?
2. Take timely action to remove weeds
Tree saplings on a green roof – these have been allowed to get out of hand
Identify the weed if you can and try to work out why it is thriving on your roof.
Weeds that are commonly found on green roofs include grass, moss and tree seedlings.
Grass is good…sort of
A weed is any plant growing in the wrong place. It might be grass between patio slabs, groundsel in the greenhouse or moss in the lawn.
Should you need help or advice on green roof weeds, the green roof maintenance team have a wealth of knowledge and experience.
What began as a dirty roof can quickly lead to larger, more expensive roof problems. Plants can’t grow without moisture. If water isn’t draining off your roof properly, there’s an opportunity for seeds to germinate. When roof drains, scuppers and gutters are blocked by environmental debris and growing plants, they cannot divert water away and ponding water and/or leaks are likely.
Saturated leaves and blowing dust can quickly become rooftop compost, the ideal place for wind-borne seeds to grow. The conditions are ideal for algae, mildew, and mold to grow too.
Imagine years without cleaning; your car would be covered with dust and dirt. That same accumulation occurs on your roof and if left unattended long enough, seeds deposited by the wind, squirrels, or birds can make an unwanted rooftop garden flourish. While this can occur with any type of roof, ballasted systems are especially problematic because the rock traps dirt.
The Damage Trees Cause to Your Roof
Does it really cause damage? Out of sight, out of mind, right? Unfortunately, no. Spouting plants on the roof and in drains and gutters is a big problem. (For the sake of clarification, we’re not talking about vegetative roofs in this blog.)
If you’ve just discovered vegetation on your roof, it’s evidence of one (or both) of the following:
The root system of plants, shrubs, and trees will quickly destroy a roof membrane and the insulation beneath.
How to Prevent Tree Growth on a Roof
That tree would never have grown if there had been routine roof maintenance. Performing the following regularly (yearly or more often, as needed) will prevent problems from taking root.