August is the last month of genuine peak-season care before the fall slowdown begins. Growth is still strong on most tropicals, though some species — particularly calathea — start to show the first hint of slowing in late August as days shorten perceptibly. It's the last sensible repotting window of the year, the month when outdoor-summering plants need to come back in before nighttime temperatures drop, and the point when thrips from open windows and returning outdoor plants can introduce an infestation that carries all the way into winter if you don't catch it early.
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What's happening to your plants in August
August sits at the transition between peak summer and the beginning of fall deceleration. Day length is noticeably shorter than July — we're losing around two minutes of daylight per day by mid-August, and by the end of the month the change is visible. Light intensity is still summer-strong, but the angle is lower than June and the afternoon sun doesn't hit the same positions indoors that it did in July.
Physiologically, fast-growing tropicals like pothos, heartleaf philodendron, and monstera are still actively growing. Some more seasonally sensitive species like calathea and pilea may start to slow perceptibly in late August — fewer new leaves, longer intervals between new growth. This is normal. It's not a care problem; it's the plant sensing the change in photoperiod.
The August care window matters: repotting in August gives plants roughly 6–8 weeks of warm growing conditions to establish roots in fresh soil before growth slows in October. Repotting in September or October gives roots less time to settle before winter dormancy, which is why August is the last practical repotting window of the year for most plants.
Southern hemisphere readers: your August is our February — the late-summer transition notes here apply to your late-summer period, roughly January through March.
Light this month
August light is still strong but measurably different from June. The sun's arc is a bit lower, morning and evening light comes at different angles than solstice, and south windows that were receiving overhead sun in June now see a slightly lower-angle light that penetrates deeper into a room.
The practical effect: some plants that needed to be well back from south windows in June can move slightly closer in August. But I don't rush this — the change is gradual, and a plant that was getting scorched in July should stay protected until you verify that its actual leaf surface isn't receiving direct sun.
In August I also start thinking about what's going to happen to my north-window plants as September approaches — that's when north-facing rooms start to feel genuinely low-light. August is the time to consider moving any plant that was barely getting by in a north room to a slightly better spot while there's still enough light to sustain the transition.
Window guidance for August:
- South windows: Still need shade protection for tropical shade-lovers, but you can start testing whether shade-lovers that were pushed very far back can move slightly closer to the light.
- East windows: Excellent for most tropicals all the way through August. Morning sun is warm and the afternoon shade prevents heat stress.
- West windows: Still intense in August, especially in heat waves. Afternoon sun through west glass is still summer-strong — keep shade-lovers protected.
- North windows: Fine for low-light species through August, but start thinking about repositioning anything marginally lit here before September's longer nights begin.
Watering adjustments
August watering is still at summer frequency for most plants, but if you start to notice plants taking longer to dry out than they did in July — typically in the last week or two of August — that's the seasonal slowdown beginning and a signal to start adjusting. Don't over-water a plant that's slowing its growth simply because you've been watering it on a June/July schedule.
As always: check the soil, don't water on a fixed schedule.
Practical August watering notes:
- Plants still in peak growth (pothos, monstera, heartleaf philodendron, spider plant) continue at summer frequency — water when the top 1–2 inches of soil are dry.
- Plants starting to slow (calathea, pilea, some ferns) may need water slightly less often in late August than in July. Watch for the soil staying moist a day or two longer than usual — it's telling you something.
- Outdoor plants coming back in will need a watering schedule recalibration. Outdoor pots typically dry out faster than indoor ones; you may find a plant that needed water every day outdoors now needs it every 5–7 days inside.
Use the watering frequency calculator to recalibrate when conditions change significantly.
Humidity
August humidity indoors is still driven by AC, which continues running at close to full capacity through the month in most of the country. The humidity battle from July continues — NC State Extension notes tropical houseplants prefer qualitatively higher humidity than typical AC-driven indoor air provides.
There's sometimes a brief humidity spike in August in climates with late-summer monsoon patterns or when a tropical system affects broader regions, but for most indoor environments, AC is still the dominant driver and conditions remain dry.
Late August does bring the possibility of nights cool enough to open windows, depending on your climate and USDA zone. Open windows bring natural outdoor humidity in but also bring outdoor pests in — particularly thrips, which are abundant in late summer as outdoor gardens finish their peak season. If you're opening windows in August, inspect plants near those windows for thrips on new growth weekly.
Maintain the same humidity strategies from June and July: humidifier near sensitive plants, grouping, and pebble trays. Don't let up on humidity management just because summer feels like it's winding down — your AC is still running, and calathea still cares about dry air in August.
Pest pressure this month
August pest pressure comes primarily from two directions: the ongoing summer spider mite and thrips populations established in June and July, and a new influx from outdoor sources — both from open windows and from plants returning from outdoor summer vacations.
Thrips are the August headline pest. They're abundant in outdoor gardens in late summer, and they find their way indoors through open windows and on returning outdoor plants. New growth flushes on heartleaf philodendron, pilea, and pothos in August are the primary targets. Look for silvery streaking, distorted leaf surfaces, and tiny fast-moving insects on new leaves and in the folds of unfurling leaves. Confirm with the spider mites vs thrips vs whiteflies guide if needed.
Spider mites remain active through August in dry AC-driven air. Continue checking leaf undersides when you water.
Outdoor-returning plants are the most significant pest-introduction vector of the year. Any plant that spent summer outdoors — even in shade — has been exposed to the full spectrum of garden pests for weeks. Quarantine all returning outdoor plants for at least 2–3 weeks, away from your indoor collection, before reintroduction. Inspect thoroughly for spider mites, aphids, scale, mealybugs, and thrips before clearing them.
When you find active pest damage, act immediately:
I isolate first, then treat — a plant with active thrips or spider mites sitting next to your clean collection can spread the infestation within days.
Tasks for this month
- Repot any remaining root-bound plants now — this is the last practical repotting window before fall slowdown. Plants potted up in August have 6–8 weeks to establish roots in fresh soil.
- Bring outdoor-summering plants back inside before nighttime temperatures drop below 55°F — most tropical houseplants are cold-sensitive and can sustain damage at temperatures in that range. Quarantine on return.
- Inspect all returning outdoor plants carefully for pests before reintegrating them with your indoor collection — mandatory 2–3 week quarantine.
- Check open-window plants for thrips — late summer is peak thrips season outdoors, and open windows are an entry point.
- Continue fertilizing through August at full strength; September is when most guides recommend tapering.
- Start monitoring light for plants in north and low-light positions — August is the time to move marginally-lit plants to better positions before September dims further.
- Clean all leaves on large-leafed plants before the growing season winds down.
Plants to focus on in August
Heartleaf Philodendron (Philodendron hederaceum)
Heartleaf philodendron is still growing actively in August and is one of the more thrips-prone plants this month because of its ongoing production of tender new growth. I check the new unfurling leaves closely — look for silvery streaking or distortion in the leaf surface before it fully opens.
The ASPCA lists Heartleaf Philodendron as toxic to cats and dogs via insoluble calcium oxalates. Keep away from all pets. See heartleaf philodendron care for full growing notes.
Heartleaf philodendron prefers consistently moist soil per NC State Extension — in August, check it every 3–5 days and water before soil goes dry.
Jade Plant (Crassula argentea)
August is a good month for jade plant care. It's been in active growth through summer and may benefit from a top-dress of fresh soil or a light repot if it's become rootbound. Jade plant is more drought-tolerant than most tropicals — it stores water in its thick stems and leaves — so it's one of the plants that handles any late-August schedule disruptions with grace.
The ASPCA lists Jade Plant as toxic to cats and dogs — clinical signs include vomiting, depression, and incoordination. Keep away from pets. See jade plant care for full details.
In August, water jade plant when the soil is dry through at least the top half of the pot. Bright indirect to direct light is preferred.
Pilea (Pilea peperomioides)
Pilea (Chinese money plant) grows steadily through August, often producing small offset plantlets at the soil surface. These can be carefully removed and potted up in August with good success rates in warm conditions. By September the window for establishing new plants from offsets narrows.
Per NC State Extension, pilea is considered non-toxic to cats and dogs — though ASPCA does not have a standalone entry in the warehouse. It's generally regarded as pet-safe.
Water pilea when the top inch of soil is dry. It tolerates somewhat lower humidity than calathea or alocasia, making it a more forgiving option for the dry August indoor air.
Pothos (Epipremnum aureum)
Pothos is still growing well in August and remains the most forgiving plant in the collection. By late August it may start to slow marginally, but you won't notice unless you're counting leaves. August is a good month to take stem cuttings for propagation — they root readily in water or moist soil and will establish well before winter.
The ASPCA lists Golden Pothos as toxic to cats and dogs via insoluble calcium oxalates. Keep away from pets. See pothos care.
Monstera (Monstera deliciosa)
Monstera is still pushing new leaves in August, though the pace may slow slightly compared to June and July. August is an excellent month to repot a rootbound monstera — the warm conditions support fast root establishment in fresh soil. Go up one pot size and use a chunky, well-draining aroid mix.
The ASPCA lists Monstera deliciosa as toxic to cats and dogs via insoluble calcium oxalates. See monstera care.
Snake Plant (Sansevieria trifasciata)
Snake plant is the one to reach for if you know August is going to be a neglect month — travel, busy schedules, or simply the end-of-summer slowdown in attentiveness. Its thick leaves store water, it tolerates north to bright indirect light, and it doesn't care much about humidity. Water it when the soil is dry through at least 2 inches depth, which in August may mean every 10–14 days.
The ASPCA lists Snake Plant as toxic to cats and dogs via saponins — nausea, vomiting, and diarrhea can occur. Keep away from pets. See snake plant care for full details.
What NOT to do in August
Don't bring outdoor plants back inside without quarantining them. This is the cardinal rule of August. Two weeks of isolation, careful inspection for pests, and treatment if needed before the plant rejoins your collection. I have made the mistake of skipping this exactly once, and I spent the following three months dealing with a thrips infestation across half my collection.
Don't repot after late August into September. Once nights start cooling and growth begins to slow, repotting stress is harder to recover from. If you've missed the window this year, wait until March.
Don't stop checking for spider mites and thrips. Late summer is not the time to relax pest monitoring. If anything, August through September is when outdoor pest populations peak and window-entry risk is highest.
Don't continue fertilizing at the same rate as you approach September. August is still appropriate for full-strength fertilizing, but late August is the time to make that your last full-dose application for the year — September care guides recommend tapering to half-strength as the growing season winds down.
Don't ignore plants near open windows. If you're ventilating with open windows in August evenings, check the plants nearest those windows for thrips and aphids weekly — late summer outdoor populations are high.
Don't let newly repotted plants go in direct sun immediately. Repotting disrupts roots, and a plant that just went into new soil is temporarily less able to cope with heat and direct light stress. Keep newly repotted plants in bright indirect light for the first week or two.
Frequently asked
Should I fertilize in August?
Yes, through August. Plants are still actively growing and can use nutrients productively. I apply a balanced liquid fertilizer monthly through August, then taper to half-strength in September and stop fertilizing entirely in October for most plants. Fertilizing a plant that's slowing its growth in fall doesn't help — the unused nutrients sit in the soil and can build up as salt deposits that damage roots. August is the last full-dose month for most plants.
My plant is dropping lower leaves in August. Is that normal?
It depends on the plant. Pothos and heartleaf philodendron regularly drop older lower leaves — the plant prioritizes the newest growth and lets the oldest leaves go. If the leaf yellowing and drop is confined to the oldest leaves at the base or along old vine sections, and new growth looks healthy, it's probably normal senescence. If yellowing is happening on newer leaves, spreading rapidly, or accompanied by mushy stems, that points to overwatering, root rot, or a pest problem. Check the roots and soil moisture first.
When exactly should I bring outdoor plants back inside?
The practical rule: bring plants back in before overnight lows consistently approach 55°F. Most tropical houseplants are sensitive to temperatures below that threshold and can sustain cell damage from brief cold exposure. In zone 6, that might mean mid-August for safe outdoor placement; in zone 9, you might have until October. Check nighttime forecasts regularly in August and don't rely on the calendar alone — an early cool snap can damage plants left outdoors even in the warmer zones. And remember: every day outdoors is another day of pest exposure, so the sooner you bring them in (with proper quarantine), the less you're rolling the dice.
Sources: ASPCA — Heartleaf Philodendron · ASPCA — Jade Plant · ASPCA — Golden Pothos · ASPCA — Swiss Cheese Plant (Monstera) · ASPCA — Snake Plant · NC State Extension — Heartleaf Philodendron · NC State Extension — Pilea peperomioides · NC State Extension — Plant Toolbox · UC IPM — Thrips · UC IPM — Spider Mites