Even the most avid gardeners can struggle with how to wake up the late summer garden after a long, hot summer. August through September can be a tough time for gardens and gardeners alike.
Did you know there’s a term for this time of year, called serotinal? The word comes from the Latin adverb sērō (late)” and means ‘pertaining to or occurring in late summer.’ It’s the midpoint between mid-summer and autumn.
This is an awkward time in the garden, when things seem to have come to a screeching halt, and everything is a little muted.
Especially our plants with various shades of green that were once vibrant with notes of chartreuse, lime, and deep, rich greens that made the garden feel so lush.
Now, it seems these enthusiastic shades have been dulled by the heat, blending in with one another to create a less exciting garden.
And when combined with perennials that have called a time-out, taking a break from the unrelenting heat, it can be downright depressing strolling through the garden.
Fortunately, as hot and tired as I feel, my garden still has plenty of bright spots. Which is why I’ve updated this post to include loads of plants that come into their own when the others poop out.
I’m not talking about those plants that might produce a few token repeat blooms – I’m talking about plants that produce TONS of blooms.
Plants that not only tide the garden over until the cooler temps of fall put on their own show – but plants that thrive in this serotinal season (like this sedum ‘Autumn Joy’, left, which is just now starting to step on stage.)
So here we go!
Rudbeckias – Full to part sun, perennial, zones 3-9, deer-resistant
I adore all rudbeckias, reminding me of my grandmother’s zone-6 Lake Tahoe garden, where they grew with wild abandon. Here are some of my favorites.
Rudbeckia laciniata (Cutleaf Coneflower)
Native to Missouri, this pollinator-favorite prefers more water, though it does well with average water at my family’s Lake Tahoe garden.
Plus, without ample water, its typical aggressiveness is easily curtailed, keeping this rampant spreader in check.
With average water, it grows to 4’x3’, but if grown with more water (or along a stream, where it’s really happy) it’ll definitely spread around and grow to 9’ tall!
Rudbeckia triloba ‘Prairie Glow’
Like the more common rudbeckia triloba (below), it also has a multi-branching habit, but instead of the typical gold-yellow blooms, these flowers glow with shades of mahogany, red, orange, and yellow.
Don’t the colors ‘pop’ when planted in front of burgundy foliage?
Once established, it grows to 36” x 18” and may re-seed if you’re lucky.
This is the common variety, yet nonetheless just as spectacular as any other!
The 1-inch flowers cover the tall multi-branched stems, but what the flowers lack in size, they make up for in quantity.
It begins blooming mid to late-summer and will be covered with hundreds of blooms all the way through October.
If happy, it will re-seed throughout your garden, which I don’t mind, as rudbeckias can be short-lived.
And with so many babies sprouting up, I always have plenty to pass along.
Rudbeckia ‘Henry Eilers’
I adore prairie plants, which is why when I first spotted this variety at the Bellevue Botanic Garden, I vowed then and there to find some for my own garden (speaking of which, I’m speaking there again May 8th, 2024 – if you live in the area I’d love to say ‘hi’!)
This is a tall variety, growing to 4-5’, with tons of starry golden-yellow late-summer blooms with spoon-shaped petal tips. Very unusual!
While I’ve never seen them available in local nurseries, I’ve ordered mine from Bluestone Perennials.
Even though the tags say they need moist soil, mine have done well with average water. I just make sure to provide at least 3-inches of mulch to help retain the moisture.
Rudbeckia hirta ‘Autumn Colors’
This is a full-sun, short-lived perennial (mine have lasted only 2-3 years), but boy, are they worth replacing when the time comes!
This native variety is much shorter than the others I’ve previously mentioned, growing to just 2’x2’.
The flowers, though, are much larger – 3 to 4”, in shades of deep orange, red, gold, and yellow.
Bouvardia ternifolia (Firecracker Bush) perennial, full to part-sun, zones 7-10, deer-resistant
By far, the most popular post I’ve written is 25 Heat-Loving, Deer-Resistant Perennials for HOT Summer Days. So, if you’ve read that post you might see a few repeat performers in this post about late-summer blooming plants.
That’s because a few plants are THAT amazing – they keep pumping out the blooms for weeks on end, all the way through fall.
Bouvardia is no exception, as it looks just as good today as it did in July. Native to Texas (and the southwest) this is an amazing perennial that will attract every hummingbird in the area to your garden.
It has stiff, upright stems that reach 3-4 feet tall, and once the temps begin to heat up, the vibrant scarlet red flowers appear (and never stop until the first frost!)
Helianthus ‘Lemon Queen’ full-sun, perennial, zones 4-9, deer-resistant
As some of my regular readers know by now, I’m a sucker for anything that grows unusually tall (click here for some of my favorites!), and I’m excited to say that ‘Lemon Queen’ doesn’t disappoint.
Give it a few years, and this perennial sunflower will grow to a towering 8’ x 4’, with loads of 2-3” soft yellow flowers, bringing lots of sizzle to your late summer garden.
This is a Midwest native variety of helianthus, preferring moist soil, but it does just fine in my garden with average water.
I have loads of aster varieties throughout my garden. They’re indispensable for blooming their little hearts out during this transitional time in the garden.
Anything that blooms for weeks at a time, nourishes tons of pollinators, and withstands marauding deer and rabbits has my vote!
Aster laevis (Smooth Aster) zones 4-9
The Smooth Aster is unique in that it’s tall and airy looking. It quickly grows to 3-4’ on tough stems that don’t easily flop over.
Leaves are long and smooth to the touch versus other asters (hence its common name.)
I love how mine looks nestled against the faded blooms of the cenolophium denudatum (Baltic Parsley. Click here and scroll down the post to see what this gorgeous umbilifier looks like in the spring!)
Aster divaricatus (Wood Aster) zones 3-9
This is my favorite groundcover aster, perfect for cascading down a rock wall.
The Wood Aster prefers shade, with a bit of morning sun to encourage blooms.
Despite the internet saying it’s somewhat thirsty, in my gardens in Los Altos, Granite Bay, and Lake Tahoe, it thrives with fairly low water.
Aster frikartii ‘Monch’ zones 5-9
I have several of these throughout my garden, most in full sun but some in partial shade (fewer flowers, but heck, at least they bloom!)
They look particularly stunning nestled among the dark foliage of Berberis ‘Concord.’
In fact, maroon and glaucous/blue is one of my favorite color combos (click here to see why!)
Blooming from July through September, I think the butterflies love them almost as much as I do.
Oh, and don’t be so quick to cut back the spent flowers of ‘Monch’ as they can add another element of interest to the winter garden (below.)
Aster tataricus ‘Jindai’ (Tatarian Aster) zones 5-8
I’m always experimenting with zone-8 plants, praying they’ll do well in my zone-9 garden. Sometimes they do, sometimes not so much.
Luckily, this Tatarian Aster loves my garden!
However, it does want a bit more water (similar to the New England Aster, below) so I have this one planted at the bottom of the hill where a naturally occurring high water table keeps it watered for me.
While the species grows to a towering 7-8′, ‘Jindai’ tops out at 3-4′ on very stiff stems, making it ideal for the middle of the border.
The profuse purple blooms of ‘Jindai’ start opening towards the end of September, and last until the first frost, making it a fantastic early-fall food source for hungry pollinators.
Aster ‘Barbados’ (New England Aster or Michaelmas Daisy) zones 5-9
This variety is a bit thirstier than the others (after all, it’s called a ‘New England’ aster which is a clue!) but it still does really well in my garden with moderate water. In the photo (left) you can see it growing with yellow solidago ‘Little Lemon’ and sedum ‘Autumn Joy – two other amazing late-summer bloomers.
And below, it’s also growing behind my agave desmetiana.
Malvaviscus arboreus (Turk’s Cap) deciduous shrub, part-sun, zones 7-10
This native shrub has been in my garden for several years, providing rich nectar to every hummingbird in the neighborhood.
While it does die back in the winter, it can quickly grow to 8-feet or more in a single season, if it has moderate water.
I give mine less water than it probably wants, which keeps it growth at a manageable 4’x4′.
Of course, I’d be remiss if I didn’t include ornamental grasses in this post about adding pizzazz to the late-summer garden.
Many grasses, like the calamagrostis, pennisetum, or betula varieties are just now starting to ‘bloom’ with their tall inflourescens.
However, in this post, the focus is on flowers.
But if you’d like to read more about how to design with ornamental grasses, and the many gorgeous varieties that have thrived in my garden – click here.
Zauschneria ‘Everett’s Choice’ (CA Fuchsia) perennial, full-sun, zones 8-11, deer-resistant
Man, oh man, my California Fuchsias are in their prime right now!
‘Everett’s Choice’ is my go-to variety of choice, as the foliage tends to have a greenish tint to it (versus many other varieties that have glaring, steely-gray foliage.)
Combine that beautiful foliage with the tiny scarlet, red-orange trumpets that cover the 1 1/2′ mound, and you have a hummingbird’s buffet.
This particular planting combination gets all-day sun, with reflected heat from my driveway. The zauschneria, lomandra ‘Platinum Beauty’, and grevillea ‘Peaches and Cream’ (behind) is perfection, looking good throughout the majority of the year.
What more could you want?
Caryopteris ‘Beyond Midnight’ and ‘Dark Knight’ (Bluebeard) perennial, full-sun, zones 5-9, deer-resistant
‘Beyond Midnight’ (left) is a Proven Winners variety and is still one of my favorite late-summer bloomers.
Starting in late July, this Bluebeard will bloom through the end of September.
The blooms are darker than many other varieties, and the shrub is more compact.
I wish you could see how many bees are on this plant (look closely, and you can find at least 4!)
This is the ‘Dark Knight’ variety which grows a bit taller (3’x3′) than ‘Beyond Midnight’ (2’x2′).
I love the repetition of blue colors happening in this combination, with the aster laevis (mentioned above) growing behind.
If you squint, you can even see the salvia azurea in the distance, further echoing the cool blue colors.
Tithonia rotundifolia ‘Goldfinger’ (Mexican Sunflower) annual, full-sun, zones 8-11, deer-resistant
I love orange flowers in the garden (click here to see some of my favorites), and tithonia doesn’t disappoint.
It’s mid-September now, and my tithonias are just now kicking into gear, with loads of buds waiting to open into 3” bright orange flowers that light up the garden.
It’s a tall annual, quickly growing to 48” (or more) x 20”, and does well with average water. I’ve heard it can be a little tricky to start from seed (anyone have experience?), but I’m definitely going to try it this year.
Vitex agnus-castus (Chaste Tree) perennial, full-sun, zones 5-9, deer-resistant
The vitex is a non-stop bloomer, starting in July and going all the way through to the first frost.
In this photo, it’s the large shrub with lavender-colored blooms, behind the bright pink salvia.
It’s a biggie, growing into a large shrub/small tree (15’x15’ or more!)
However, ‘Blue Diddley’ is a smaller Proven Winner variety that I’m dying to get my hands on, growing to a much more manageable 5’x5’.
Lantana tender perennial in zones 9-11, otherwise an annual, full-sun, deer-resistant
It seems far too many west coast gardeners are jaded by the ubiquitous lantana, and roll their eyes when I mention it.
But honestly, this is one of the most reliable late-summer bloomers there is, and nothing seems to stop it.
It takes the hottest temperatures with a grain of salt.
It thrives with very little water.
Deer and rabbits leave it alone.
And butterflies and hummingbirds adore the blooms.
Not only that, but it comes in a huge range of colors and sizes.
I will admit that lantana is mighty unattractive in the winter, with its brown, dead leaves clinging onto the stems. But c’mon…nothing’s perfect and it’s a small price to pay for all this late summer beauty.
One of my favorite varieties is ‘Dallas Red’ (in the foreground of the photo) as it has the most vibrant, rich reds and oranges I’ve seen.
The taller ‘Radiation’ is in the back, growing to 3-4′ with softer shades of orange and yellow.
So, to those who might be groaning with my commonplace suggestion, I dare you to walk outside this time of year, look at the butterflies feasting on the flowers, and not think to yourself , ‘wow, Rebecca was right – this IS an awesome plant!”
And now for some exciting news!!
Starting next week, I’ll be contributing design content for Garden Design Magazine in addition to co-hosting monthly webinars (along with president Jim Peterson.)
I couldn’t be happier!
I’ve been listening to Garden Design’s webinars over the past few years, and they’re amazing, featuring world-famous gardeners such as Fergus Garrett (head gardener at Great Dixter), David Culp of Brandywine Cottage, and Dan Hinkley – to name a few.
Next week, September 21st, Dan Benarcik of Chanticleer Gardens will discuss a topic that couldn’t be more timely – Gardening in Overtime: Getting the Most Out of Your Late Season Display.
Unlike other webinars, these are less formal, similar to a fireside chat that results in a more personal experience.
Attendees are encouraged to type their questions, which will be answered in real-time, or at the end of the webinar.
After the webinar, updated show notes are sent out (along with a link to the recording) that also includes a wrap-up of ideas and comments submitted by attendees – something called ‘Wisdom of the Crowd’ (and boy, is this crowd incredible – full of relevant advice and ideas.)
So, if you’d like to learn more about adding some late summer sizzle to your garden, click here to join, and I’ll see you next week!