Parking under trees: sap, leaves and droppings

The sticky film is often not sap

If your car is coated in a fine, tacky mist after a few summer days under a linden or maple, that is usually honeydew. Aphids feed on the leaves and drop a sugary liquid that lands as tiny specks across the roof, hood and glass. It turns grey as dust sticks to it, and on the windshield it smears when the wipers run.

Honeydew dissolves in water, so a normal wash takes it off without much trouble. The problem is that it keeps coming as long as the aphids are there, which can be most of July and August. If you park in the same spot every day, a wash every week or so is more realistic than waiting for it to get bad.

Real sap and how it hardens

Pine and spruce sap is different. It falls in larger, thicker drops and hardens into amber beads, especially in hot sun. Fresh sap often comes off in a wash. Sap that has cured for a few weeks usually will not, touchless or otherwise, because it has bonded to the clear coat.

For hardened spots, use a dedicated sap remover or isopropyl alcohol on a soft microfibre cloth, let it sit for a minute to soften the bead, then lift it off with light pressure. Do not scrape with a fingernail or a blade. Wash the area afterwards, since solvents can strip any wax or protectant from that spot.

Bird droppings need the fastest response

Trees are where birds sit, so a car parked underneath collects droppings. These are the most damaging thing on this list. As the paint heats up in the sun and cools at night, the clear coat expands and contracts around the dropping, and it can leave a dull, etched outline that stays after the mess is gone.

Deal with them within a day or two if you can. Lay a wet cloth over the spot for a few minutes to soften it, then lift it off. Wiping it dry drags grit across the paint. If an etched mark is already there, a wash will not fix it. That usually needs polishing by hand or a detailer.

Leaves, seeds and blocked drains

In the fall, wet leaves stuck to a light-coloured hood can leave brown tannin stains if they sit through a few rainy days. Brush them off rather than letting them dry in place.

The bigger issue is drains. Leaves and maple keys collect in the cowl at the base of the windshield, where the cabin air intake usually is, and in the channels around the sunroof and trunk lid. When those block, water backs up and can leak into the cabin or footwells. A wash will not clear them. Lift the hood and pull the debris out by hand a few times each fall, and check your owner's manual for where the sunroof drains are on your car.

Spring pollen

In April and May the yellow-green film on everything is pollen. On its own it is mostly a nuisance, but it soaks up morning dew and can stain if it sits wet for long. It rinses off well. A basic wash is enough for pollen and honeydew; save the deeper packages for when there is salt or mud underneath.