This post was updated on May 1, 2024
Black Mold from Tree Pollen
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 it?
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 of 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.
Best Cleaner for Removing Mildew from Trees
The RAD Guard will remove the black mildew and green algae stains from your wood and deck stains and will prevent them from returning for 1-2 years: RAD Guard Mildew and Algae Cleaner and Preventer
We did all the prep etc and didn’t think about the pollen in the air. First coat of Cabot Gold oil stain is on and there is a yellow layer of pollen on top. What do I do? Cabot says to apply the second coat within 7 days. Do I try to clean off the pollen, wait, just do the 2nd coat and pray it doesn’t turn black??
There is nothing you can do at this point outside of removing all the Cabot and starting over. If you do not, it will probably mildew on you from the pollen that has dried into the stain.
Hello,
I stained my deck with Armstrong in July. It looked perfect. Wood is 2 yrs old. We have pine trees next to the deck. Since the rains started here in WA, my deck is not looking so good. The deck that is not covered and is closer to the pine trees is looking like mildew /mold is coming to the surface. Help! Is there a cleaner I use now, or wait till Spring?
Wait until Spring to prep and recoat.
I have a few questions regarding staining and tree pollen. Our deck was completed around Thanksgiving, KDAT pressure treated pine, with cedar railings. We planned to wait the couple of months advised, but there were so many rainy days, it was pushed out to March, and we did not know about the wet application option.
The deck was cleaned this past Wed. with Restore a Deck cleaner and brightener. Then, we were hit with very high pollen counts (6800 plus), for the past few days, and learned that the oil based Armstrong Clark stain we had picked wouldn’t work. The tree pollen period will likely last a few weeks.
My questions are:
1. If I understand correctly, if we switch to water based stain, then we can go ahead and stain, even if pollen days are high? Or, is it best to wait anyway? Various pollen seasons, in the Southeast area of metro Atlanta, will be ongoing for months, but the current pine tree pollen is the big yellow stuff.
2. If we do move forward, and order water based stain (Defy Extreme or the Restore a Deck that you recommend), how long is our Restore a Deck cleaning effective until, as it may take time to get the stain shipped? Or, will we need to reclean and brighten again?
3. When we get the stain, do we just blow off the pollen with a leaf blower. Or, is it best to rinse, as well? If so, is the wet application of Restore a Deck better in this regard, as we could stain more quickly?
Thanks
1. Pollen can feed mildew growth if it is trapped in a stain. It does not matter if oil or water-based. Less potential issues with water-based as it dries and cures much faster.
2. Always try to stain within 2 weeks of prep or you will need to lightly redo the prep.
3. It depends on how long it has been, how dirty it is, and how much pollen landed on the wood. Rinsing would be better in general.
OK. Thanks. This sentence in the above article had made it sound like water based would avoid it (“Another option to avoid this from happening is to use a water-based deck stain.). But, it sounds like there is still some risk, though. Since you mention rinsing is better, do you suggest using the Restore a Deck stain since you can rinse before applying, since you can apply it wet? Or, can you do a light rinse a couple hours before any water based stain? We are trying to blow off the pollen every other day, as well, while as we will be waiting a week or so for the new stain to ship in.
Avoid but not 100% stop. The RAD stain would make it easier and faster to get it done. Other water-based stains cannot be applied the same day as the prep.
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?
No and no. Bleach will harm the stain and it is not possible to just remove the mildew without having to reapply the stain.