Deck Stain Turns Black from Tree Pollen 4.3/5 (3)

by Deck Stain Help
Black Mold from Tree Pollen

Black Mold from Tree Pollen

Updated February 2020

Deck Stain Turns Black from Tree Pollen

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When Your Deck Stain Turns Black from Tree Pollen, what happened and how to fix?

You’ve followed all the steps to ensure your deck stain project has a beautiful finish. You properly prepped it, allowed for it to dry before staining (unless you used Restore-A-Deck), then stained it meticulously in a beautiful semi-transparent finish. However, you are left with black mildew spots on the finished wood surface down the road. How did this happen?

Black Mold from Tree Pollen

We hear complaints about this problem within our community, and we’ve seen it with our own eyes when we survey wood decks. One thing you may have not considered is whether the deck is near a pollinating tree. Tree pollen can fall on a drying oil-based deck stain project and promote the growth of mildew which causes the black specks or spots. To prevent this, make sure you start your wood stain project when your trees are not going through their peak pollination phase if using an oil-based stain. If the pollen falls on the drying wood stain, it can attach to the surface of the wood, promoting the growth of mildew. Always make sure you are properly cleaning your wood deck prior to brightening and staining as well.

Another option to avoid this from happening is to use a water-based deck stain. The best brands we have used and tested for a water-based penetrating semi-transparent stain would be the Restore-A-Deck Wood Stain and the Defy Extreme Wood Stain.

If your deck has turned black due to tree pollen, it is important to recognize and tackle the problem. Stripping the wood using a quality wood deck stain stripper or wood deck cleaner will remove the mildew. Pick a high-quality stain that contains mildewcides and mold inhibitors, as low-quality stains can be a source for mildew growth themselves. Proper maintenance includes a light wash every couple years followed by a recoat of the same quality deck stain. As always, make sure your wood surface is not around any tree pollen before tackling a deck stain project.

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Sally Dwyet
Sally Dwyet

Just restained our pressure treated deck this spring and have a ton of black mildew. Can we clean it without having to restain? If so is bleach a good way to clean it?