Spider mites on houseplants

Flip a leaf over: tiny moving dots and fine, silky webbing mean spider mites. Rinse the plant hard in the shower, then wipe or spray every leaf underside with insecticidal soap once a week for three weeks — that’s how long it takes to catch the eggs that hatch after the first round.

Spider mites aren’t insects; they’re tiny relatives of spiders, about the size of a grain of salt. They suck juices out of leaf cells, and in a warm, dry room a few can become thousands in a couple of weeks.

How to confirm it’s spider mites

Sign	What it looks like
Stippling	Tiny pale or yellow dots all over the leaf, like it was sprinkled with salt
Webbing	Fine silk under leaves and where leaves meet stems — not a big spider web
Moving dots	Specks that crawl, usually on the leaf underside
Dull, bronzed leaves	Leaves lose their shine and turn yellow-brown
Leaf drop	Badly affected leaves dry up and fall

The white paper test: hold a sheet of white paper under a leaf and tap the leaf sharply. If specks fall and start crawling, you have mites. Smear one: spider mites leave a red or green streak.

Which plants get them most

Plants in warm, dry rooms get hit hardest — especially in winter when the heating is on. Common targets: English ivy, calathea, parlor palm and other palms, dracaena, alocasia, and plants that spent the summer outside. Bringing plants in for winter? Check them first →

The 3-week plan

Eggs survive most treatments, so one round is never enough. Mark these on your calendar:

Day	What to do
Day 1	Isolate the plant. Cut off the worst leaves. Rinse every leaf, top and underside, with lukewarm water in the shower.
Day 1	Once dry, spray or wipe all leaf undersides with insecticidal soap (or a horticultural oil labeled for houseplants). Follow the label.
Day 4	Check with the white paper test. Rinse again if you see webbing.
Day 8	Second soap/oil treatment, all surfaces.
Day 15	Third treatment.
Day 22	Final check. Two clean checks in a row? Move it back with the other plants.

Tips that make the treatment work:

• Coverage is everything — mites hide under leaves and in leaf joints.
• Test soap or oil on one leaf first and wait a day; some plants (ferns, for example) are sensitive.
• Don’t spray in direct sun or when the plant is very dry.

Prevent them from coming back

• Raise humidity a little and keep leaves clean. Mites love dusty, dry leaves. A monthly shower or wipe helps more than you’d think. (Does misting help? Not much — here’s what does →)
• Quarantine new plants for two weeks before they join the others.
• Check leaf undersides every time you water. Catching ten mites is easy; catching ten thousand isn’t.

If you also see tiny flies around the soil, that’s a different pest: fungus gnats.