15 Perennial Flowers That Grow Better When Planted In August (Gardeners Know This Trick!)

Every senior gardener I've ever worked with tells me the same thing about August. It feels like the garden is winding down, so the work should wind down with it. That's the biggest mistake you can make this month, and it's the reason so many spring gardens open up weak instead of full. The perennials on this list don't care that the calendar says summer is fading. They care about one thing, warm soil. And while the air starts to cool off, and that ground underneath still holds on to the summer Roots are doing more growing than they will at almost any other point in the year. I've put together 15 perennials for you, and we're counting them down from 15 to 1. Number 6 is a plant a lot of folks write off as background filler, and by April it's usually the first thing visitors notice in the yard. Number 1 has quietly become a favorite among gardeners who don't want to fuss over their beds every week. And once you hear why, you'll understand exactly why I saved it for last. I'm John Sam, and this is Seniors Gardening Advice, the channel built around gardening that's easier on the back and better for the borders. None of what's coming up requires heavy digging, hauling bags of soil across the yard, or spending your whole weekend on your knees. Most of the real work on this list happens underground, out of sight, which means the effort you put in now is small compared to what you'll see waiting for you when the weather warms back up. If a full season of color with less bending and less guesswork sounds good to you, go ahead and subscribe now so you don't miss what we cover next. Let's get into the list, starting with the plant that rewards a little patience more than almost anything else you'll put in the ground this year. Before we get to number 15, it helps to understand why August works so well in the first place, because the same few rules apply to almost everything on this list. Soil that's still warm from the summer sun acts like a slow cooker for roots. Cooler air overhead signals the plant to ease off on pushing out new leaves and start sending that energy underground instead. That's why a perennial planted now can outgrow one planted in spring, even though it looks smaller going into winter. A few habits will carry you through this entire list. Dig the hole wider than the root ball rather than deeper, since most new roots spread out sideways before they ever go down. Water deeply right after planting, then keep the soil evenly moist for the first few weeks while roots settle in, easing off once the ground cools for good. Skip the high nitrogen fertilizer this time of year. It encourages soft new leaf growth that won't have time to harden off before frost, and it can pull energy away from the roots that actually need it. A two-inch layer of mulch, pulled back slightly from the crown of the plant, holds moisture and steadies the soil temperature through those first shaky weeks. Keep those habits in mind as we go, because I won't repeat them for every single plant. One more thing worth mentioning. If you're gardening in a colder zone, aim to get everything on this list into the ground within the next few weeks so roots have enough time to settle before the first hard freeze. In milder climates you have a bit more breathing room, sometimes stretching into September. A long-handled trowel or a bulb planter can save your knees and your lower back on days when you're working through several of these at once, and a simple soaker hose laid along a new bed makes watering in the weeks ahead far less of a chore than dragging a hose across the lawn every evening. Number 15. Catmint. If you've ever wanted a border that looks tidy without you standing over it every weekend, catmint earns its spot at the very start of this list. Its silvery green foliage and soft purple flower spikes shrug off drought once established, and bees treat it like a buffet all season long. Give it full sun and soil that drains well, since soggy roots are about the only thing that bothers this plant. Space new plants roughly 18 to 24 inches apart to give the mounding habit room to fill out. Deer and rabbits tend to leave it alone because of the strong scent in the leaves, which makes it a forgiving choice if wildlife has been a problem in your yard. Planted in August, catmint has enough time to build a root system before winter, so by the time the first warm days of spring arrive, you'll already have a full, rounded mound ready to bloom instead of a bare twig working its way back from scratch. If the mound ever starts to look leggy in mid-summer, a quick trim back by a third brings on a fresh flush of flowers within a couple of weeks, and that's about as much upkeep as this plant will ever ask of you. Number 14. Coneflower. This one grows a long taproot, and that single detail explains almost everything about how to treat it. Getting that root established before the ground freezes matters more than almost any other step you'll take with this plant, which makes August planting far more forgiving than trying to squeeze it in during the heat of July. Coneflower wants full sun and soil on the leaner side, since rich, heavily amended beds tend to produce floppy stems and fewer of those daisy-shaped blooms with the raised center cone. Once it's in place, resist the urge to move it, since disturbing that taproot sets the whole plant back. Leave the seed heads standing through winter instead of cutting them down in fall. Finches and other small birds will work through them on cold mornings, and the plant holds its shape well against frost even after the petals are long gone. By its second spring, a single coneflower planted now can already be wide enough to split into two or three new plants for other corners of the yard. Number 13. Russian Sage. If your yard has a hot, dry corner where nothing else seems to want to grow, this plant was practically built for it. Russian Sage thrives on neglect in the best possible way, tolerating poor, rocky soil and long dry spells that would leave most flowering perennials wilting by afternoon. Its silvery stems and airy lavender-blue flower spikes bring a soft, almost hazy texture to a border, and the aromatic foliage keeps deer from bothering it. Give it full sun and sharp drainage, and resist the temptation to feed it richly, since too much fertility just makes the stems floppy and weak. Space plants two to three feet apart, since a mature clump spreads wider than it looks in the nursery pot. One habit worth remembering. Leave the old stems standing through winter for a little structural interest, then cut the whole plant back hard in early spring rather than in fall, since the old growth actually helps protect the crown through the coldest months. Because it takes a season or two to reach full size, don't be discouraged if this one looks sparse its first spring. The payoff shows up in year two and only gets better from there. Astilbe For a shady corner that's always felt a little empty, astilbe brings feathery plumes of pink, red or white that seem to glow against dark green, fern-like foliage. Unlike most of the drought-tolerant plants on this list, astilbe wants consistently moist soil, and it will let you know quickly if it dries out by browning at the edges of its leaves. Partial to full shade suits it well, with a little morning sun tolerated in cooler climates. Mulch heavily around the base to hold moisture, since its roots stay fairly shallow and dry out faster than you'd expect. Space new plants 12 to 18 inches apart, and plan on dividing established clumps every three or four years once the center starts to look thin. Planted in August, alongside hostas or ferns, astilbe fills that gap between spring bulbs and summer flowers with almost no extra work once it's settled in. Choose varieties in a few different bloom times if you have the room, since staggering early, mid and late season types keeps color going in that shady corner for months instead of just a couple of weeks. 11. Coral Bells This plant earns its place for foliage alone, long before it ever sends up a single flower. Coral bells come in shades of amber, purple, lime and near black, holding that color through most of the year in milder climates, which makes it one of the few perennials on this list that still looks good in the middle of winter. Give it part shade, since too much hot afternoon sun can scorch the leaves and well-drained soil that never stays soggy. The one detail that trips people up, keep the crown sitting right at soil level. Bury it too deep, and the whole plant can rot from the center out. Space plants 12 to 18 inches apart, and check on them after a hard freeze and thaw cycle in late winter, since the crown can heave up out of the ground and needs to be gently pressed back down. Come late spring, wiry stems covered in tiny bell-shaped flowers rise above the foliage and draw hummingbirds in for a closer look. Because the color holds through fall and often into winter in milder areas, a small grouping planted along a walkway now can carry a bed through the months when almost nothing else is contributing anything worth looking at. 10. Japanese Anemone This is the last of the new additions, and it's here because it solves a problem a lot of gardens have, color, once the peak of summer has already passed. Japanese anemone sends up tall, wiry stems topped with pink or white flowers in late summer and into fall, right when most borders are starting to look tired. It prefers part shade, especially afternoon shade in warmer regions, along with rich, evenly moist soil. The first year after planting, it tends to sit quietly and build roots, rather than put on much of a show, so don't judge it too quickly. Once it settles in, it spreads by underground rhizomes and can travel further than expected, so give it a spot with room to wander, or a hard edge like a path to keep it contained. Mulch well after planting this August to protect the young roots through their first winter, and by the second or third fall, you'll have a drift of movement and color that most late-season gardens are missing entirely. Cut the old stems back once frost finally takes them down, and resist digging around the base in spring, since new shoots can pop up further out than you'd expect as the clump matures. That covers the six new additions, and now we're moving into familiar ground, nine perennials that reward August planting more reliably than almost anything else you can put in the soil this year. Peony If you only think about peonies once they're already blooming in spring, you're already behind. The gardeners who get the biggest, fullest blooms do the real work in August, months before a single flower shows up. Here's the piece that decides everything. The buds on a peony root, called eyes, need to sit one to two inches below the soil surface. Bury them any deeper, and you can end up with years of healthy green leaves and no flowers at all. Give peonies full sun, at least six to eight hours a day, along with rich, well-drained soil. Skip high nitrogen fertilizer here too, since it pushes leafy growth at the expense of blooms and raises the risk of disease. Varieties like Sarah Bernhardt and Festiva Maxima are known for producing some of the largest blooms in the whole garden when they're given this kind of head start in late summer. Bearded Iris This plant has one of the strangest planting rules you'll come across, and getting it wrong is an easy way to lose next year's blooms before winter even arrives. Bearded Iris grows from a rhizome, a thick underground stem, and in late summer, that rhizome is resting, which makes it the ideal time to plant or divide it. Here's the part that surprises almost everyone. The top of the rhizome should sit at, or just barely below the soil line, sometimes even slightly exposed. Bury it too deep, and trapped moisture can rot it before it ever gets the chance to bloom. Mound the soil, lay the rhizome on top, and spread the roots down each side. Full sun and sharp drainage aren't optional here, and mulch should never be piled directly over the rhizome, since trapped moisture is the fastest way to lose the whole plant before spring. If you're dividing an older clump while you're at it, cut the fans of foliage back to about a third of their height before replanting, which keeps the newly cut roots from having to support more leaf than they can handle while they're still getting established. Bleeding Heart If this plant seems to vanish completely by the middle of summer, that's not a problem, that's exactly how it's supposed to work. By August, all of its energy has already moved underground into fleshy roots, so above the soil, it looks finished, while underground, it's actually preparing for next spring. Set the crown level with the soil in rich, moist soil, impartial to full shade. Those buds need a long stretch of cold, roughly 16 to 20 weeks below 41 degrees, to trigger the heart-shaped blooms it's known for. Since the foliage disappears for part of the season, plant ferns or hostas nearby so the bare patch of soil doesn't stand out while you wait for it to return. Number 6 Creeping Phlox A lot of folks treat this plant like a filler and tuck one lonely pot into a corner, which undersells exactly what it can do. Creeping Phlox spreads by rooting as it grows, so planting in August gives every stem months to knit itself into a solid mat before spring arrives. Space plants 6 to 12 inches apart, in a staggered pattern rather than a straight line, and it fills in noticeably faster. It wants full sun and soil on the dry, rocky side, actually struggling in rich, wet ground. Plant it now, and by April, you could have a carpet of pink, purple, or white flowers covering ground that would otherwise still be bare mulch well into the season. Number 5 Columbine This plant teaches impatient gardeners a lesson fairly quickly. Expecting it to look full and established in its first year, usually leads to disappointment. But that's not a failure, that's simply the plan. Columbine spends its first fall building a deep taproot, and August planting gives that root system months of a head start before the ground freezes solid. Give it partial shade, especially in hot regions, along with well-drained, fertile soil. Leave it sitting in wet ground too long, and the crown can rot before it ever reaches its potential. Keep the crown level with the soil line rather than buried. One trick worth trying, let a few spring flowers go to seed instead of deadheading everything, since Columbine self-sows readily, and a single August planting can multiply into dozens of blooms over the following seasons. Those distinctive spurred blooms also happen to be a favorite waypoint for hummingbirds passing through in spring, so a small cluster near a window or a porch gives you a front row seat. Number 4 Hellebore Also known as the Lenten Rose. While most of the garden is still asleep in late winter, this plant is already putting on a show, sometimes pushing flowers straight through late snow. Hellebores hate being moved once they're established, so choosing the right spot now matters more than with almost anything else on this list. Plant it under a deciduous tree, where summer shade protects it and winter light still reaches the evergreen leaves. Dig the hole 2-3 times wider than the root ball, but no deeper, and disturb the roots as little as possible while settling it in. Space plants 12-24 inches apart since crowding traps moisture and raises the risk of leaf spot in damp spring weather. Leaves that look tattered or spotted by late winter can simply be trimmed away right before the flower stems rise, which tidies up the plant and lets those early blooms take center stage without any competition. Number 3 Siberian Bugloss If deer or rabbits treat your hostas like a buffet every summer, this plant solves that problem without asking you to give up a beautiful shade garden. Its rough, heart-shaped leaves naturally resist both, so while nearby hostas are getting chewed down, this one keeps looking just as good as the day you planted it. August planting lets it settle into shade before the real cold sets in. Give it partial to deep shade and consistently moist soil since baking in hot, dry conditions will leave those attractive leaves looking tired fast. Mulch around the base to hold moisture through the last hot stretch of summer, and by spring, small sky-blue flowers seem to float above silvery foliage, bringing life back to the shadiest corner of the yard. Number 2 Oriental Poppy One of the easiest mistakes to make with this plant is giving up on it too soon when it disappears by mid-summer since that's simply what oriental poppies have evolved to do. That dormant window in August is the exact moment to plant or move one. This plant grows a deep taproot and once it's in the ground, it hates being disturbed again so it pays to get the placement right the first time. Give it full sun and sharply draining soil since sitting in wet ground can rot the roots long before spring ever arrives. Since the foliage disappears for weeks at a stretch, plant something sprawling nearby, like baby's breath, to cover the gap. By late spring, the reward is blooms the size of your hand in colors bold enough to look almost painted onto the garden. A single established clump can hold that kind of presence in a border for well over a decade which makes the small effort of getting the spot right this August one of the better long-term trades you'll make in the whole garden. Number 1 Dianthus Also called Pinks This is the plant I've been building toward the entire list because it settles in faster than anything else we've covered. A lot of gardeners underestimate Dianthus since it looks small right out of the pot but its fine, fibrous roots establish with remarkable speed giving it plenty of time to root in firmly before the ground freezes. Give it full sun, 6 to 8 hours if you can manage it along with soil that drains sharply and leans neutral to slightly alkaline. Space plants 8 to 12 inches apart to keep air moving and prevent powdery mildew from taking hold. In colder regions, a light layer of straw after the ground freezes protects the crown. Just remember to pull that mulch back in early spring. Plant it this August and by spring you'll have fragrant blooms and early color from a plant that looks like it's been established for years. 15 perennials, all of them ready to go into the ground this month and every single one rewards the gardener who gets moving now instead of waiting for spring to sort itself out on its own. None of them demand a perfect gardener either, just a little patience and a real willingness to trust that the quiet work happening below the soil is worth it in the end. So which one earns a spot in your beds first? Let me know in the comments and tell me your growing zone while you're at it since someone gardening in your exact climate is probably reading through those comments too. This is Seniors Gardening Advice and if you'd rather spend next spring enjoying a full garden instead of scrambling to catch up, subscribe so you don't miss what we plant next.