The sand on your putting green is turning dark or black. Here is why.

Green sand starts light, uniform and clean, so a change in color is always something added to it, never the sand aging on its own.

• Pine pollen paste. Rain turns the yellow spring pollen load into a paste that works down into the sand and darkens it as it dries.
• Live-oak leaf tannins. Leaves dropped in April release tannins as they break down, staining the sand a brownish shade wherever leaf litter sits and is not cleared.
• Algae and biofilm. In shaded, damp spots that never fully dry, a thin dark film forms on the sand and fiber the same way it does on any damp turf.
• Bird droppings. A perch, a wire, or a favorite spot overhead leaves repeated small deposits that darken and can smell.
• Sand that was never kiln-dried or clean to start. Play sand or beach sand carries organic fines and moisture that proper green sand does not, and it can look dingy from day one rather than darkening over time.

Location does most of the diagnosis. A dark ring or patch under an oak or pine points to pollen paste or leaf tannins. A shaded strip along a fence or under a canopy that stays damp longer than the rest of the green points to algae or biofilm. Scattered small dark spots, especially near a wire, gutter or roofline the birds favor, point to droppings. And sand that has looked slightly gray or dingy since the green was built, rather than darkening gradually, points to sand that was never the right grade. Rub a pinch between your fingers: a gritty, dry, dusty texture is usually organic debris; a slick or slightly slippery feel points to algae or biofilm, and a faint musty smell confirms it.

1. Brush hard against the grain over the dark area to lift and loosen whatever has settled into the sand.
2. Pull out the worst of the contaminated sand rather than just burying it under new sand.
3. Treat the spot with a turf-safe oxidizer for tannin and organic staining, or a turf-safe algaecide where the film is biological. Never bleach; it strips fiber color and does not solve what caused the darkening.
4. Top-dress with fresh kiln-dried green sand and brush it in evenly so the treated spot matches the rest of the surface.

Pine pollen starts on warm days in February, peaks in March and into early April, and live-oak leaves come down through April right behind it, so a green on the Grand Strand takes its heaviest organic load in a six-to-eight week spring window. Cleaning during that window just means doing it again in a few weeks, since more pollen and leaf litter is still coming down. The better timing is a thorough brush, pull and top-dress once that window has closed, so whatever darkened the sand over spring does not sit through the humid months that follow and turn into algae. Our coastal turf maintenance calendar lays out that timing against the rest of the yard's year, since a green under the same trees usually needs its clean-up on the same schedule as the lawn around it.

A quick brush lifts surface pollen and moves loose debris, but tannin staining that has soaked into the sand grains and biofilm that has taken hold in a shaded low spot both come back within days of a surface-only pass. Sand that was never kiln-dried does not improve with brushing at all, since the problem is the sand itself rather than what landed on it; that sand needs to be pulled and replaced with the right material, not treated in place.

Handle light, occasional pollen dust yourself with a stiff brush between visits. Call when the dark patch keeps returning within a few weeks of clearing it, when it smells musty rather than just dusty, or when you are not sure whether you are looking at algae or simple debris. That work is an algae and organic-buildup treatment folded into a putting green restoration, priced after we see the green; a typical backyard green falls in the same range as our Premium Restoration bands, $299 to $899, by size and condition.