Will zinc strips harm my garden or local waterways?

The question matters more in Greater Victoria than in most cities because so many roofs drain toward water. Lots in Cordova Bay, Ten Mile Point, Brentwood Bay and along the Colquitz, Bowker and Millstream creeks send roof runoff to the sea or a salmon stream within a few hundred metres, and the CRD's stormwater system in the core municipalities is largely separate from sewage treatment, so what goes down a Fairfield or Oak Bay downspout can reach the shoreline untreated. That is an argument for strips over repeated powder applications, and for redirecting downspouts, not an argument against moss control.

Gardens are the other local concern. Victoria's rain barrels, vegetable beds under the eaves and ornamental ponds in Saanich and Oak Bay backyards all sit in the runoff path. A rain barrel fed from a slope with a fresh powder treatment should be bypassed for the first few storms; a barrel below a zinc strip that has been in place for years is a much smaller issue. Copper gutters, common on older Rockland and Uplands houses, are the one thing zinc sulfate demonstrably damages, so on those homes a copper strip is the better match.

A strip works by shedding a trace of metal ions each time rain runs over it, which is enough to stop spores establishing on the roof but is spread across every rainfall for years. A powder or heavy liquid application delivers the whole dose in the first few storms, which is when it can burn foliage under the eaves and reach a pond in a concentration that matters. Extension guidance treats the strip as the low-impact preventive and the removal of existing moss as the necessary first step; the two together mean fewer chemical applications over the roof's life.

Walk the lot and note where each downspout discharges. Any that feed a pond, a rain barrel used on vegetables, or a swale that runs to a creek should be redirected to a splash pad on lawn or gravel for the first storms after any treatment, and permanently if a powder is used. Rain barrels can be bypassed with a diverter. Overspray on plants under the eaves is rinsed off with a hose the same day. None of this is complicated; it just needs to happen before the moss company arrives, not after.

• Map downspouts to pond, barrel, bed or creek
• Bypass rain barrels for the first storms
• Rinse foliage under the eaves the same day
• Ask the applicator what the product is and its label guidance

What product are you applying and can I see the label? Is it a powder or a liquid? Is it safe on copper gutters and flashing? Where will the runoff go and should I redirect anything? Would strips reduce how often you need to come back? A reputable Victoria moss company will answer all five without hesitation and will often suggest a strip-plus-occasional-treatment plan for roofs that drain toward water.