De-Mossing a Slick Brick Walkway
Jennifer Nawada discusses ways to keep that brick walkway from getting slippery
My shaded brick walkway is covered with moss and becomes very slippery when it rains. I've poured bleach and vinegar and salt on the moss, but it's still there. Is there a way to get rid of it without harming my plants? —G. Cannon, East Greenwich, R.I.
I'm pretty sure that your bricks are actually covered with algae, not moss. Algae gets as slick as ice when it's wet, while moss forms a spongy cushion that isn't as dicey to walk on. Moss is also opaque. If you can see the brick through a greenish or black film, then you have algae.
You're on the right track with bleach and vinegar. Undiluted white vinegar destroys algae by drying it out. Diluted chlorine bleach is also an effective algicide, but isn't safe for plants. A better choice would be an oxygen bleach, such as OxiClean.
Whichever solution you choose, apply it with a spray bottle or garden sprayer, then scrub with a soft bristle brush. Rinse thoroughly while the brick is still wet. Repeat a second time, if necessary. To help keep your walkway clean, trim overhanging branches to bring in more sunlight and air circulation and help the bricks dry. The faster they dry out, the longer it will take for the algae to grow back. When it does, just hit it with more vinegar or oxygen bleach.
Jennifer Nawada is a landscape designer, a certified horticulturist, and the owner of Nawada Landscape Design in Boston. She appears regularly on TV episodes of Ask This Old House.