August Indoor Plants: How To Manage Summer And Shifting Light

The Calendar Year may get paid commission for purchases made after clicking a link on this page. 
This website is for inspiration purposes only. The content provided is meant to spark creativity and ideas, not to serve as professional advice or as endorsement.

August has a distinct feel for plant people. On the surface, it still looks and feels like peak summer. Everything is lush and green, and the days are still long. But there’s a subtle shift happening that plants pick up on before we do. The light is changing. The nights are getting noticeably longer. And if you pay attention, you start to see the first hints that summer is winding down. August is about enjoying what’s left of the season while quietly preparingfor what comes next.

What’s Actually Happening in August

August sits in an interesting position in the plant calendar. It’s still very much summer, with warm temperatures and good light levels. But the days are shortening noticeably after the June solstice, and by the end of August, the change is genuinely significant. You’re losing roughly two to three minutes of daylight every day through August.

For most houseplants, this hasn’t triggered any significant changes yet. Growth continues at a good pace through most of the month, though you might notice it slowing slightly toward the end of August compared to the explosion of June and July. Some plants also subtly slow their water uptake.

August is also a month of two halves when it comes to the weather. Early August often feels like the height of summer. By late August, cooler nights in the UK and northern US start to signal the approach of autumn. It’s worth noting this shift because it affects outdoor plants in particular.

For Southern Hemisphere readers in Australia, New Zealand, and South Africa, August is the equivalent of late winter and early spring. The February and March posts in this series are more relevant to your current conditions.

Watering in August – Still High But Starting to Ease

Watering needs in August remain high, particularly in the first half of the month. Outdoor plants still need daily checking in warm spells, and indoor plants in sunny spots are still drinking quickly. That said, as temperatures gradually ease toward the end of August, you’ll notice some plants not drying out quite as fast as they were in July.

This is the month to start paying closer attention to the signals your plants are giving you, rather than just watering on a fixed schedule. A plant that needed watering every two days in mid-July might stretch to three days by late August. Following the soil rather than the calendar remains the most reliable approach.

One August-specific issue is that outdoor plants can be suddenly waterlogged after dry spells, which can quickly waterlog the compost. If you’ve had a dry July and August suddenly brings heavy rain, check the drainage of outdoor pots and promptly tip away any standing water in saucers.

The RHS guide to watering container plants remains a solid reference for adjusting watering through the seasons.

Feeding – The Last Big Push of the Season

August is the last month when feeding at full fortnightly strength really makes sense for most houseplants. Growth is still active enough to justify it, and the nutrients help plants build strength as autumn approaches.

That said, toward the end of August, some people begin reducing feeding frequency slightly for plants that are clearly slowing down. There’s no hard rule here- follow what your plants are telling you. A plant that is still producing vigorous new growth in late August can continue regular feeding. A plant that seems to have slowed down might benefit from reducing watering to once every three weeks.

August is also a good month to give flowering plants one final high-potassium feed to encourage any last blooms of the season. Hoyas, begonias, anthuriums, and jasmine can all produce late summer flowers with the right encouragement.

Down to Earth Fertilizer in the US and Tomorite in the UK are both good high-potassium options widely available this time of year.

Bringing Outdoor Plants Back Inside – When and How

If you moved plants outdoors for the summer, start thinking about bringing them back indoors in August. You don’t necessarily need to do it yet, but having a plan is important.

The general rule is to bring tropical houseplants back indoors before overnight temperatures consistently drop below 10 degrees Celsius (50 degrees Fahrenheit). In the UK, this can begin in September in some areas. In northern parts of the US and Canada, it can happen even earlier.

August is the time to start monitoring overnight lows in your area. The Met Office in the UK and Weather.gov in the US both give reliable overnight temperature forecasts. Don’t wait until you see a cold forecast and have to rush everything in at once.

Before you bring plants back inside, inspect them very carefully for pests. Outdoor plants can pick up all sorts of hitchhikers over summer, including aphids, spider mites, vine weevils, and slugs hiding in compost. Check every surface of every leaf, inspect the compost, and consider repotting any plant that has been outdoors all summer into fresh compost.

The RHS pest identification guide is invaluable for this process.

Acclimatising Plants Coming Back Inside

This is something I got completely wrong in my first year of plant keeping. I brought everything in from outside all at once in early September, and several plants dropped leaves dramatically. The transition from full outdoor conditions to indoor conditions is more disruptive than it seems.

Outdoor conditions offer more light, better air circulation, and natural humidity from rain. Indoor conditions are dimmer, drier, and stuffier. Plants need time to adjust to that shift just as they needed time to adjust going the other way in spring.

Bring plants indoors gradually if possible. Start by moving them to a sheltered outdoor spot in the shade for a week, then to a bright porch or conservatory, and finally to their indoor position. If you can’t do it gradually, at least give them 2 to 3 weeks near your brightest window before moving them to their final winter spot.

Expect some leaf drop. It’s normal, and it doesn’t mean you’ve done something wrong. Most plants stabilise within a few weeks once they’ve adjusted to indoor conditions.

Gardeners’ World has a helpful step-by-step guide to this process that I wish I’d found earlier.

Late Summer Propagation – Last Chance This Year

August is the last reliably good month for propagation in the Northern Hemisphere. After this, as light levels drop and growth slows, cuttings take longer to root and success rates fall. If there are plants you’ve been meaning to propagate all summer and haven’t got around to it, now is the time.

Water propagation in August still works quickly. Most cuttings will root within two to three weeks in a bright spot with the remaining summer warmth. Pothos, tradescantia, philodendrons, and begonias are all excellent choices for August propagation.

Division is another technique to use in August for plants that have become very large and congested, such as spider plants, peace lilies, and calatheas. Dividing a large plant into two or three smaller ones gives each division fresh space and compost, and you end up with more plants for free.

Establishing rooted propagations before autumn gives them time to settle in before winter. A cutting rooted in August can become a reasonably established plant by November.

Gardeners’ World’s propagation hub has guides for all the techniques and species mentioned here.

Starting to Think About Autumn Care

August isn’t quite the time to switch into autumn mode, but it’s the right month to start thinking about it. A little forward planning in August makes the transition to autumn much smoother for both you and your plants.

Think about where your plants will spend winter. Do you have enough good light spots for everything? If you’ve accumulated more plants over the summer, as many of us have, you may need to consider how to position them to receive adequate light once outdoor brightness is gone.

It’s also worth thinking about which plants might need a grow light this winter. If you had plants struggling with low light last winter, August is a good time to research and invest in a grow light before you actually need it. Having it set up before autumn arrives is much less stressful than scrambling in November.

Finally, take stock of your compost, pots, and equipment. If you’re running low on potting mix or need new pots for plants you’re bringing back inside, August is the time to stock up before garden centres start reducing their ranges in autumn.

The Spruce’s guide to grow lights remains a reliable reference for choosing the right setup.

My August Plant Checklist

August is about enjoying the tail end of summer while starting to look ahead. Here’s what I’m working through this month.

Continue checking outdoor plants daily and water generously in warm spells. Maintain fortnightly feeding, but start monitoring for signs of slowing growth toward month-end. Begin monitoring overnight temperatures and plan when to bring outdoor plants indoors. Inspect any plants that have been outside for pests before they come back in. Get any remaining propagation done while summer warmth and light are still on your side. Consider winter light spots and invest in a grow light if last winter was a struggle. And take a moment to appreciate your plants at their peak because autumn is just around the corner.

As always, the RHS and American Horticultural Society are brilliant general resources to have to hand.

Are you noticing any changes in your plants as summer winds down? I always find August bittersweet. Everything looks so good, but you know it won’t last much longer. Would love to hear what you’re doing to make the most of the last of the summer growing season.