Tiny black dots stuck to the siding like tar, usually on the wall nearest the mulch bed. Not dirt, not mold, and not something a pressure washer will fix.
Artillery fungus is a small fungus that lives in decaying hardwood mulch. It is named for what it does: it builds pressure in a tiny cup-shaped fruiting body, orients itself toward the brightest thing it can see, and fires a sticky spore mass at it. On a house, the brightest thing nearby is light-colored siding, and it can reach well up a wall.
What lands is a dot roughly the size of a pinhead, dark brown or black, and coated in an adhesive that sets hard. That adhesive is the whole problem. This is not a stain sitting on the paint, it is a small object glued to it.
| What you see | What it probably is |
|---|---|
| Pinhead dots, raised enough to feel with a fingernail, concentrated on the lower wall by a mulch bed | Artillery fungus |
| Flat green or black patches, worse on shaded and north-facing walls | Algae or mildew, which a soft wash removes |
| A chalky even fade on sunny walls that comes off white on your hand | Oxidation, which needs different chemistry |
| Dark streaks running down from the roofline | Roof runoff, see black streaks on a roof |
| Dots on cars, windows and the mailbox as well as the house | Artillery fungus, which does not care what it hits |
Height is the most useful clue. Artillery fungus is launched from ground level, so it thins out as you go up and usually stops somewhere between the first-floor windows and the eaves. Algae does not follow that pattern.
Because the spore mass is bonded rather than deposited. Force removes what is resting on a surface, and this is not resting on anything. Turning the pressure up far enough to shift the dot will crack vinyl, drive water behind the courses, or strip paint, and even then it often leaves a stain behind where the adhesive was.
You may get some of it, particularly if the specks are fresh. Older ones have had time to set and to weather into the surface, and those are the ones that stay. Anyone promising to pressure wash artillery fungus off a wall completely is promising something the material does not allow.
Fresh spore masses, in the first days, are the only ones that come off with any consistency. Once they harden the odds drop sharply.
A fingernail, a plastic scraper, or a nylon brush and patience will lift individual specks without damaging siding. It is slow, and on a badly hit wall it is not realistic for the whole elevation.
A soft wash will not remove the fungus but it removes everything else, which makes what remains visible and stops you fighting two problems at once.
On siding that has been hit for several seasons, meaningful improvement is a realistic goal and a spotless wall usually is not. We would rather say that up front than after taking your money.
Everything above is temporary if the mulch bed stays the same. This is the step that actually ends it.
Artillery fungus needs damp, decaying hardwood. Take that away and the problem goes with it, which is why mulch choice matters more than any cleaning method.
If you are choosing between cleaning the wall again and changing the mulch, change the mulch. Cleaning is an annual cost, the mulch is a one-time change.
We will look at a wall and tell you honestly what is achievable. Often that means a house wash to clear the algae and grime, hand work on the worst-hit sections, and a straight conversation about the mulch bed. If the specks have been there for years, we will say so rather than sell you a wash that cannot fix it. Call (919) 698-3669 or send a close-up photo and we can usually identify it from that.
“Siding and windows on the same day and the whole house looks lighter. Careful with the beds and easy to schedule.”
“They transformed the outside of our house. The siding looks brand new and they were careful around all my flower beds.”
“They brought the color back on our vinyl siding after another company left it chalky. Night and day.”
The white film that comes off on your hand is not dirt. It is the surface of the siding breaking down, which is why washing the house does not fix it.
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