The Best Late-Summer Flowers For Your August/September Garden

In mid August, it’s sometimes hard not to look at your garden and throw in the towel. By that, I mean take out the pruners and cut down all the moldy, dried out stems or simply turn a blind eye to the whole debacle. But that would be a shame with so many late-summer flowers just now coming into their own. It just takes a little advance planning and some careful pruning and you can have a garden that keeps flowering all the way until fall.

I know what I’m talking about, not only as a designer, but because I co-chair a demonstration garden in Maryland that must be in peak flower in August in time for the County Fair. Located on the grounds of the Montgomery County Agricultural Center, the garden is funded by the Master Gardener program and plays an integral role in educating the public. The Fair falls at a time of year, however, that can be hard on flowers not only because it’s getting late in the season but also because there are invariably wide swings in weather.

A view of our demo garden with the cow ‘show barn’ in the back

Come late July, I often lay awake at night wondering just how the garden will remain in flower. And this year, our demo garden endured more challenges than usual, including extremes in temperature, a prolonged period of drought and a 10-day deluge of rain. Additionally, a cold spring led us to plant later than usual (every year we add or replace some flowers) only to watch the the temperatures soar 20 degrees above normal the following day. It was a perfect storm of garden-related disasters that made us all wonder what would possibly be left for the Fair.

It was a miracle then, that when we opened the garden to the public yesterday, it looked better than ever.

Blanket Flower (Gaillardia) is a member of the sunflower family

How did we do it? Upon reflection, I think our success hinged on four important things: 1) Choosing late-summer flowers; 2) Diligent pruning to increase or delay blooms; 3) Proper irrigation; and 4) Planting annuals and bulbs to fill out bare spaces.


Following are the perennials that are in full flower today in our August garden, many of which started blooming in early July. Other late-summer flowers like Japanese anemones, goldenrod, Joe Pye weed, physostegia, dahlias, zinnias and many plants in the aster family waited until August to begin putting on a show.

We supplemented these flowers with such dependable late-flowering shrubs as abelia, hydrangeas ‘Annabelle’ and ‘Limelight’ and Knock-Out Rose.

Hydrangea arborescens ‘Annabelle’

Planting late-summer flowers in the right places (sun or shade, back or front of the border) sets the August/September garden up for success from the start. It pays to educate yourself on what species bloom when and then design your garden around the seasons you most like to enjoy it.


I’ve written a lot previously about the importance of deadheading and why it encourages a plant to produce more flowers. But there’s another secret to pruning: judicious and early removal of blooms can also cause a plant to bush out and most importantly, it can delay flowering. Depending on what time of the season you make your cuts and by how much, you can coax plants to bloom at times later than they are naturally programmed to do.

Red hibiscus

My go-to reference for all types of pruning is The Well-Tended Perennial Garden by Tracy DiSabato-Aust. I’ve used it for years to get plants to bloom longer and at times they aren’t accustomed to. This in turn has helped our Master Gardener team create unique color combinations in our demo garden and orchestrate things so that our plants are in peak flower come Fair-time.

New Dawn climbing rose with balloon flower in the background

Starting in mid June, we hard prune many of our flowers, lopping off sometimes as much as a third of the plant. This encourages the plant to bush out instead of becoming leggy. And, if we get our timing right, the flowers are delayed until the beginning of August, or just in time for the Fair.

Here are two examples:

Daylilies. in addition to snapping off the daily dead blooms (daylilies are called daylilies for a reason), we make sure to immediately remove any of the bulbous seed heads that start to develop. In the plant world, once the seedpods start to develop, the plant thinks it’s done for the season and stops flowering.

Removing spent blooms as often as possible will prolong daylily flowering

By diligently removing the dead flowers and pods (as well as cutting all spent stalks down to the ground) the plant gets the message to keep on blooming. Using this technique, we’ve kept some of our daylilies blooming for twice as long as they usually do.

Echinaceas. These sturdy flowers start blooming in our garden in July but can get long and leggy by August without some prudent intervention. We continuously remove the flowers as soon as they start to dry out, making our cuts down along the stem where we see the newest flower just starting to develop.

Echinacea purpurea, sneezweed and salvia ‘Victory Blue’

By continuous pruning, we keep our coneflowers thick and blooming pretty much until the end of summer.


At the demo garden, we use a drip system of irrigation. It works relatively well until someone at the fairgrounds decides to turn off the main water source. This year we installed a timer and spoke with the fairgrounds staff to get everyone on the same page. Still, there were many times, especially with new plantings, that we needed to call on our team to hand water.

Purple physostegia and artemisia ‘Powis Castle’ make a great combination

Although it seems obvious, I cannot emphasize enough the need to water. Drip irrigation alone is rarely sufficient in hot climates to get new plants to establish properly. We always supplement our drip system with hand watering during dry spells, making sure to water long and deep. Deep root watering is always better than a short surface spritz, which only teases the roots before quickly evaporating.


Finally, nothing beats zinnias and dahlias for filling in bare spaces in the late summer garden. Zinnias come into their own by late August and my own dahlias at home keep flowering until well into October. It’s a great pick-me-up to see all these happy, bright flowers appear suddenly at the end of the season.

Zinnia mix in the late summer garden

We plant our (potted) zinnias in the garden in July and prune them down as they grow to encourage them to thicken up before blooming. The dahlias go in the ground in June. And both will be continuing to brighten our demo garden well after the Fair has ended.


Managing Hydrangeas: To Prune Or Not To Prune And Other Existential Questions

To prune or not to prune? That is one of the quintessential gardening questions. Recently I asked a top landscaper in Middleburg, Virginia to weigh in on the issue. “When is the best time to prune hydrangeas without destroying next year’s flowers?” I asked. Her reply?

“Never,” she said with a laugh. “But your best shot is after they’ve bloomed.”

It turns out that knowing how and when to prune hydrangeas involves first, knowing what kind of hydrangeas you have growing in your garden. Different varieties require different pruning methods. Prune at the wrong time and you risk trimming off next year’s blooms. It all starts with knowing whether your hydrangeas flower on old or new wood. Continue reading

The ABC’s Of Deadheading And Why It Produces More Flowers

Regular deadheading ensures the blooms keep coming all season long

Ever been frustrated by a beautiful plant that suddenly stops blooming? It’s time for a haircut. Regular deadheading is an essential practice in the life of a garden. Not only does it keep plants looking neat, but it encourages more blooms over a longer period of time. There’s nothing quite like getting a plant to re-flower that looks like it’s called it quits for the season.

What is deadheading?

Simply put, it’s the practice of removing faded or dead flower heads from a plant. Deadheading not only keeps a plant looking attractive, it encourages it to keep on blooming.

Dried poppy seed heads

Why does deadheading work?

Because the goal of all plants is to grow, set seed and die. As flowers start to fade, the plant pours its energy into producing seed heads. By removing dead blooms, you prevent the plant from setting seed, which in turn keeps the plant’s energy focused on producing more flowers. The result is a healthier, more vigorous plant that blooms for a longer period of time.


While deadheading benefits all blooming plants, the world of flowers is diverse and has different requirements. Depending on the species and variety, particular flowers require particular kinds of deadheading.

Here are tips on how to deadhead 6 popular varieties of flowering plants:

1. Clusters of flowers with leaves on their stems

Purple garden phlox

For tall, leggy plants like phlox, yarrow, daisies (or plants that have leaves on the lower stem), the best strategy is to deadhead just before the blooms die back completely.

As soon as flowers begin to wither or brown, use a pair of pruning shears or a sharp knife to cut off the spent blooms.

A good rule of thumb is to reach into the plant and remove the spent flowers back to the first or second set of leaves. This not only helps hide the cut, but it encourages the plant to bush out more as it produces new blooms. I vary the lengths at which I cut to keep the plant shapely.

2. Flowers with no leaves on their stems

Long-stemmed orange daylily

For flowers like daylilies and hostas that have no leaves on their stems, cut the entire stalk back to the base of the plant once it has finished flowering.

3. Salvias

Multiple flower spikes of salvia make pruning tedious

Once the initial flush of flower spikes start to brown, salvias often appear to be done for the season. With proper deadheading, however, you can encourage them to keep blooming through the summer.

Take a look at the plant and you’ll see that there are actually three flower stalks growing together – a central one surrounded by two, smaller ones on the side. As soon as the central stalk starts to brown, remove it. This will encourage the side shoots to grow.  Once the side shoots lose their color, cut them off too. Deadheading perennial salvias in this way can encourage the plant to re-bloom at least twice and sometimes three times during the season, especially if you feed it mid way through the summer.

4. Bushy plants with small flowers

Bushy perennial, Coreopsis verticillata

Bushy perennials like coreopsis can be encouraged to produce a second round of blooms past their standard flowering time.

Since it can be tedious to deadhead so many tiny flowers, I grab big chunks of the stems with spent blooms in one hand and shear them back with a pair of long-blade shears in the other. This not only encourages the plant to re-bloom a week or so later, it keeps thinks looking tidy.

5. Roses

With roses, the number to know is ‘5’

Most of us know that roses need to be deadheaded to flourish. Remove withered blooms by pruning back to above a five-leaflet leaf, cutting on an angle.

6. Annuals

Geraniums need consistent deadheading to look their best

All annuals need to be deadheaded regularly to thrive (with the possible exception of begonias, in which case I prune the leaves.) Popular annuals like geraniums and petunias must be constantly snipped, pinched or cut back to keep flowers looking neat and to encourage blooming. For a more in-depth tutorial on how to prune these annuals, click here for my blog post How To Keep Your Potted Plants In Shape All Summer.’


Butterfly weed is a prolific self-seeder

Some flowers, like columbine, echinacea and butterfly weed are prolific self-seeders. If you’re looking to produce lots of new baby plants, leave the seed heads on and they’ll quickly spread around your garden.

Don’t be afraid to get out those pruners!

It’s rare to damage a plant by cutting it. Use common sense while removing spent flowers, taking care to hide your cuts under existing foliage. You will be rewarded with a flush of new blooms!


Weed ID: Get To Know What You’re Pulling

“My flower is an educated weed.” – Luther Burbank

Summer is coming and many of our plants are bursting into flower. But while we celebrate, there’s another less attractive family of plants that is springing into life as well. These are the dark cousins of our ornamentals: the perennial and annual weeds. The bane of all gardeners, they stubbornly crop up each year, seemingly unfazed by our attempts to remove them.

I started delving into the shadowy world of weeds a few years ago when a member of my garden club gave us an odd assignment. She handed each of us a sheet of paper on which were illustrated a dozen garden-variety weeds. Then, she asked us to “locate” them in her garden. Needless to say, we pulled a lot of weeds that day. I wasn’t thrilled.

However, the experience ended up peaking my interest in this unwelcome form of vegetation.

Weeds are fierce competitors

Weeds compete with other garden plants for water, sunlight and nutrients, often in very aggressive ways. In Maryland, Creeping Charlie is one such example, as it delights in spreading rapidly by runners and carpeting the garden with its fan shaped leaves. (Though pulling it can be particularly satisfying because it comes up in large mats.) Other weeds like crabgrass, or worse, hairy bittercress that spits up tiny seeds if you touch it, are hard to eradicate and decidedly much less satisfying to remove.

It’s important to remember that, just like ornamental plants, weeds are classified by their life spans. They’re either annual (growing from seeds spread the previous year), biennial (completing their vegetative growth in the first season and flowering in the second) or perennial (springing up from established roots that survived the winter.) Herbicides are generally targeted to annual species, while perennial varieties can be much harder to kill. Perennial weeds, in fact, can easily regrow from seemingly dormant stolons, rhizomes, tubers and of course seeds.

Unlike our finicky ornamentals, weeds can grow anywhere

Over the past few years, I’ve compiled a list of the more obnoxious weeds that show up uninvited in my garden. It has helped me get to know the different species and understand when and why they appear. Somehow just knowing the names of what I’m removing has made the whole process a bit more satisfying.

Here are the top ten weeds I’ll be pulling this season


Smooth green, finger-like leaves of crabgrass

Long considered a major problem weed in North America, crabgrass can produce up to 150,000 seeds per season all of which germinate in late spring and early summer. The clumping annual grass can be distinguished by its slender, finger-like leaves that spread by side shoots from a central hub. Growing to form larger and larger clumps in star-shaped patterns, crabgrass eventually becomes a dense mat that smothers grass and other weeds.

Interestingly, crabgrass is considered a symptom (and not the cause) of poor lawn health as it thrives in sparse grass that is under watered and not well fed.


Goosegrass is one of the hardest to remove

Also known as silver crabgrass, goosegrass is a prostrate, bunching grass that spreads by seed and usually emerges a few weeks after its smooth green cousin. It has dark green, thick, flattened leaves and whitish stems that radiate from a central point (which makes it easy to identify.) Small, flattened flowers emerge on stiff spikes from July to September. Unlike crabgrass, goosegrass is very difficult to remove and its seeds spread easily by wind.


Hairy bittercress spits its seeds when you pull it

A member of the mustard family, hairy bittercress has heart-shaped leaves with scalloped margins that grow from a basal rosette. The largest leaves are at the base of the plants. The weed produces tiny white flowers from spring to fall and spits its dried seeds into the air when disturbed. If you can dodge the seeds, hair bittercress is actually easy to pull from wet soil, roots and all. Just give it a good yank on the stalk.


The candle-like inflorescences of broadleaf plantain

Broadleaf plantain has large, oval-shaped leaves that grow in a ground-hugging rosette. The leaves are attached to thick green stems that resemble celery when shredded. Long slender spikes of inconspicuous tiny green flowers spring from the base of the weed from April to September. Broadleaf plantain is actually edible (as are many weeds) and is chock full of iron, minerals and vitamins. The smallest leaves (harvested in the spring) are the tastiest, imparting an asparagus-like flavor. Fresh leaves can also be crushed to treat burns, insect bites and wounds.


Bindweed is a member of the morning glory family

This perennial weed has a spade-shaped leaf with rounded tip and two pointed lobes at the base. Erect seedlings spring from underground stems that can grow to several feet long, causing the plant to bend over and begin its vine-like growth. Whitish/pink, trumpet-shaped flowers, which close each afternoon and reopen the following day, bloom from April to October. Bindweed spreads from both underground horizontal stems and seed and is considered one of the most troublesome weeds in the U.S.


The clear blue flowers of chicory

Of Mediterranean origin, chicory was grown for centuries as a salad green before it started showing up all over our lawns and roads. It has one of the truest blue flowers around. The hardy perennial grows from a deep taproot that forms a prostrate rosette of hairy leaves. From June to September, clusters of daisy-like flowers appear on stiff hairy stalks, opening early in the morning and closing about 5 hours later. In addition to the many medicinal uses for chicory, the weed’s long taproot can serve as a coffee substitute when dried.


Delicate brown flower of yellow nutsedge 

Native to North America and parts of Eurasia, yellow nutsedge is a grass-like perennial with shiny yellowish-green leaves and golden brown flower heads. The plant spreads by producing tubers from a complex shallow root system. It can grow in just about any soil or surface, including my driveway.


Mat-forming mouse-ear chickweed

Mouse-ear chickweed is a low-growing, mat-forming perennial with oval, dark grey-green leaves. The leaves are attached directly to the stem, which can be green or purple. Tiny clusters of white, star-like flowers bloom on erect 4″ stems throughout the summer. Mouse-ear chickweed forms dense mats with trailing stems.


Easy-to-pull Creeping Charlie has violet flowers

Creeping Charlie, also known as Creeping Jenny or ground ivy, lives up to its name; it creeps. It has small, fan-shaped leaves with round-toothed edges, which emit a minty scent when crushed. Tiny blue-violet flowers appear in the spring, which look quite pretty wrapped around other garden perennials. Don’t let it get out of control, though, Creeping Charlie spreads rapidly to form dense mats, setting down roots all along its stems.


Tiny fruits of mock strawberry make it easy to distinguish

Resembling common strawberry, mock Strawberry is a ground-hugging plant that spreads by hairy runners and forms crowns at nodes. Its leaves are toothed and have dense hairs on the upper surface. Yellow flowers with five petals appear from April-June followed by tiny red strawberries. The fruits are edible, but have very little taste. The plant has been used for centuries for medicinal purposes, including as a fever reducer and antiseptic.

A portion of my lawn (below) is currently being invaded by mock strawberry.

Of course, there are so many other weeds to pull, including clover, ragweed and dandelions, to name just a few. This list is by no means exhaustive. NOTE:  Remember to pull weeds when the ground is wet- it makes it a lot easier and you’re more likely to get the entire plant instead of leaving part of it in the ground. Click here for a great tutorial on fast and easy ways to remove weeds from the garden.


True-Blue Flowers: A Dozen Of The Best And Brightest

Himalayan Blue Poppy at Pennsylvania’s Longwood Gardens/Kari Wilner

Years ago, in an effort to distract my middle-school aged daughters, I dragged them to an avant-garde exhibit at Washington, DC’s Hirshhorn Museum. The show was a one-color retrospective on the works of the French artist, Yves Klein (1928-1962) and it focused on the color blue; specifically, a supersaturated deep blue created by Klein that made you feel like you had been sucked out to sea and were drowning. Needless to say, it left an indelible impression on all of us. Continue reading

Spring Bulbs: Still Time To Plant Some Of These 10 Great Varieties

Spring bulbs in a formal garden setting

Yesterday I directed the planting of two thousand spring bulbs. We placed them individually in patterns and our very capable team dug them one-by-one into the ground. When they were finished, we dressed the bulbs with a thick layer of mulch and all stepped back to admire our handiwork. The garden felt as if it were bursting with energy with so much spring promise nestled snuggly underground. Continue reading

Five Reasons Your Trees Are Failing: A Bartlett Tree Expert Speaks Out

Trees are generally admired for their surface beauty, but their health and vigor springs from what’s underground. That’s according to Dr. Kelby Fite, Director of Research for Bartlett Tree Research Lab in Charlotte, North Carolina, who spoke to Maryland’s master gardeners last week. His lecture entitled ‘Managing the Landscape Below Ground’ provided a wealth of information about how to improve the life of the trees in our landscape. According to Fite, it all starts with the soil. Continue reading

How To Successfully Grow Lavender: A Maryland Expert Weighs In

One of the best things about being a master gardener is all the great lectures you get to attend. Today’s talk following the board meeting was no exception. It happened to coincide with the very moment I was asking myself “Why is my lavender not thriving?”. Suddenly, here was professional grower Sophia Watkins, ready to answer all of my questions.

A family-run lavender farm named Soleado

Watkins runs a family-owned, sustainable lavender farm located at the foot of Sugarloaf Mountain in Montgomery County, Maryland. It is the largest lavender farm in the state. She grew up on the 286- acre farm, 26 acres of which are now dedicated to the cultivation of lavender.

Soleado Lavender Farm

The family prides itself on its long history of organic farming, a practice Watkins’ father adopted in the 1960s when the farm grew a mix of soybeans and grains. For a child, it was a fantastic way to grow up. So when Watkins and her fiancé took over the farm, they knew that they wanted to continue that legacy.

“Our goal was about preservation even more than about gardening,” she said. “We wanted to protect these special parts of Maryland and keep them alive for not only our own child but for everybody else’s children as well.”

Why choose lavender? The couple was looking to grow a sustainable perennial that deer wouldn’t eat and from which they could make products for sale. They hit on lavender not only for its drought tolerant qualities, but also for its many decorative and culinary uses. Along the way they added bees for pollination and today the farm boasts nine hives with over 40,000 bees in each, all producing lavender honey.

In a nod to Watkins’ fiancé’s Latin American roots, they chose Soleado as the name for their farm. As it so happens, in their first year of operation, they also found themselves ‘dying in the heat’ as they got things established. Soleado, meaning sunny or ‘just baking in the sun’ suddenly took on a new shade of meaning.

Tips for how to successfully propagate lavender

At Soleado, all of the lavender is grown from cuttings, a practice most nurseries have moved to given the lower germination rate of seeds. Watkins harvests soft and hardwood cuttings averaging around 5 inches. Once she has the cuttings, she strips them of their leaves and dips them in a root hormone. Her top choice for an organic one is (not surprisingly) honey.

Watkins has had the most luck with her seedlings using a ‘bulky’ growing medium that provides maximum space for roots to expand. She mixes her own from Leafgro and perlite, then she plants the cuttings in 2” plastic pots.

Once potted, the cuttings spend up to 8 weeks in partial shade or in the greenhouse (under shade cloths) until they grow decent roots. After that, they’re transplanted to the field. Watkins noted that if the seedlings are planted outside first, the process is usually faster.

According to Watkins, three is the magic number of years for a good-sized plant to establish, after which it may continue to grow for another four. What happens around year seven I asked? If taken care of properly, lavender can last a good deal longer, with 10 to 20 years not being unheard of. And some historical properties have plants that are as much as 80 years old.

A great combo, hydrangea and lavender

Once established, lavender is a sun-loving plant. No variety can tolerate shade and still produce flowers. Once the flowers are harvested, Watkins sprays the plants’ roots with fish emulsion for fertilizer. “We need to fortify them after they’ve put all that energy into blooming, “ she said.

Cut, cut and then cut again

There is so much conflicting information about when and how to cut back lavender. Watkins freely admits that her method might not suit everyone. But for Soleado, 2 to 4 times a year is ideal. They sheer their lavender like sheep, cutting back all new growth 3 to 4 times a year until the plants flower. The cutting back starts almost as soon as the seedlings are planted.

Cutting back encourages new growth

Since lavender has a tendency to open up in the middle, cutting back helps to encourage dense growth. This improves the overall looks of the plant and helps it get through the winter. It also allows more energy to go into developing strong roots, producing a thicker, healthier plant.

At Soleado, they cut back nothing thicker than a pencil, avoiding old wood. Watkins does NOT recommend cutting back old woody stems. If you absolutely must, she said to trim them back just to where the first bunch of leaves start on the bush.

They stop all cutting by the end of October.

Avoid shredded mulch

Along with lots of sun, lavender prefers to stay dry and ironically, once of its biggest threats to survival comes in the form of mulch. According to Watkins, shredded mulch is the biggest offender. Often harboring mold spores, this kind of mulch can spell death for lavender.

“What seems to really kill them is the mold spores that come in on shredded mulch,” said Watkins. “Given the amount of humidity we have (in Maryland), it’s really important to stick with a dry medium.”

If you’re using shredded mulch in the rest of your garden, Watkins advises keeping it at least 1 – 2 feet away from your lavender. At Soleado, they use crushed bluestone for mulch that they harvest from their driveway. Other great options include white gravel and seashells, both of which help to reflect light back onto the plant.

White gravel mulch

Wintering tips

Many of us have had the experience of losing our lavender plants over the winter. However, Watkins said, “Getting your plants through the winter does not have to do with size or age, even little seedlings can make it through the winter. A temperature of anything above 0 degrees Fahrenheit is OK.”

Frozen lavender

So what can we do to prepare for the colder months? The most important thing, according to Watkins, is to keep plants trimmed and thick. The thickness (or thatchiness) is what keeps the snow and ice out of the plants. (Although snow doesn’t seem to be as bad for lavender as ice.)

It’s a matter of creating a plants that have a good smooth cut on them so they become their own insulation.

No significant pests or diseases

Not only are its water needs low, but lavender is resistant to most pests and diseases. Watkins says occasionally she’ll observe spittlebugs on her plants, but that’s about all. The main concern is lavender’s super susceptibility to mold spores (mentioned above.) The best thing you can do for mold is to practice prevention.

Another great plus to lavender is that deer hate them, although Watkins observed that “Sometimes they’ll pull the seedlings out of the ground, ‘Just because.”’

Soleado Farms grows a mix of English, French and Spanish varieties of lavender. They’re always experimenting with new strains and have found that within each variety each year there are clear standouts. These days, Watkins is loving the “rabbit ear petals” on the flower tops of Spanish lavender.

Spanish lavender

To learn more about Soleado, tours of the farm and their lavender-based products, click here for the official website.


Shady Behavior: 20 Great Plants for Shade Gardens

“Ferns are the embodiment of green thoughts in a green shade and if a leafy shadow could take root, moss would surely be the result” –Hugh Johnson ‘Principles of Gardening’

I was always drawn to shady nooks as a child. In my mind, a deep green space spoke of mystery and enclosure with its long shadows and dappled play of light. This fascination has continued into adulthood where my earliest memories now inspire many of my designs, particularly when it comes to creating a shade garden. Continue reading

How to Keep Your Potted Plants In Shape All Summer

It’s that time of year again when we all head out to purchase summer flowers to plant in pots. And they all start out looking gorgeous. But, in no time the blooms fade and the stems turn long and leggy. As a garden designer, I find that this is one of the most frequent questions I am asked: What can I do to keep my potted plants in shape all summer? Continue reading