The Informal Garden in High Summer

My north bank in high summer is where most of my native plants reside, along with some favorite hybrid cultivars. By July it is like an orchestra in perpetual warm-up. Colors start trumpeting their hues. Soon soft drumbeats of rhythm and bass notes gets the whole show going, ending with a chorus of anemones in a jubiliant finale. Each year the effect is slightly different, just as a musical score varies with every performance.

I’m a total pushover for this look, I must admit. I live for it all year long. To me, jazzy colors and intricate layers of texture are as uplifting as any piece of music. So what makes a garden invigorating as opposed to visual cacophony? Is it okay to mix annuals and perennials?

First let’s look at technique, then review the best performers.

Aside from soil, light and water needs, what else should a gardener consider when planting a large, semi-wild informal area, such as a slope?

The mix of vegetation, certainly, and their juxtapositions. Most gardeners employ a few tricks, either deliberately or unconsciously. It may help to quickly review them here, and how to achieve them with purpose. And yes, it’s perfectly fine to mix some annuals in among the perennials!

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Height — I like to mix medium and medium-tall plants, or medium-tall and very tall plants. For a more controlled look in a smaller space, I use mostly shorts and mediums, with the occasional tall “see-through” variety. If adjacent plants are mostly of similar height, then by all means, feel free to introduce other forms of contrast.

Color — Existing plants will naturally dictate the color scheme, but you can tweak it for a fresh look. The space will look more unified if you limit the colors somewhat; too many shades can be jarring. A good rule of thumb: The larger the area, the more color you can introduce. If your bed is small, a monochrome palette like all pinks or all yellows will seem more expansive than multiple colors.

Texture — Texture is much more important than most gardeners realize. After all, it’s the foliage we look at most of the time. In addition to pops of contrast, a garden also needs continuity. Knowing when to preserve or repeat a texture is a skillful way to achieve that. For example, grass is an obvious example of an easily repeatable texture.

Grasses add rhythm, verticality, pattern and most of all, movement. Mix up the flower forms too. Placing thin, strappy foliage next to whorled or deeply cut leaves is an easy example. This technique makes both plants seem more interesting, because our eyes naturally focus on the edges of things, where different textures meet.

Groups vs. clusters — Decide if you will plant in massed groupings of all one variety or repeat small clusters. Both techniques work. If you have the space and want to attract pollinators, massing is more effective than clusters. This is especially true for milkweeds (and other host plants) because just a few specimens can’t sustain a hatch of caterpillars. Large areas of a single plant also helps pollinators to locate them more easily.

Random repeats — Not everyone has the room or budget for mass plantings, me included. So I use clusters, supplemented with randomly-tucked-in singles or triples repeated throughout. If you go this route, try to keep individual plants to a minimum to avoid a spotty look. You may have to do some judicious transplanting, but the end result is worth it.

Erosion Control — On a slope or bank, be sure to include a few plants with strong root systems to hold the soil in place. I rely on grasses, barberry, liriope, daylilies, joe pye-weed and “Gro-lo” sumac (rhus aromatica). All are great at stabilizing a slope even in the hardest rains.

Gro-lo sumac is an especially good “solution” for places where little else will thrive, or areas that are not the center of attention. This form of sumac is unaffected by disease, pests or plant toxins, so it’s perfect under black walnut trees. Even better, it requires no care. In fall the foliage turns burgundy-red. It does sucker but very slowly; this trait helps create a tenacious groundcover over time. Occasionally I trim the tips of the branches for a neater, fuller appearance, but it’s not necessary.

Ease of Maintenance — Weeding a steep bank is a pain (literally) for the weeder, and sometimes presents dangerous footing. So I plant things there that require as little care as possible: nothing that needs regular dividing, pruning, staking or deadheading. I mulch the bare sections and weed early in the season. That way I can safely ignore the entire bank from July to September. Any weeds that do get a foothold can wait until I clear the bank in late fall or winter. In other words, plan ahead.

Go native— Natives and nativars are among the hardiest, least demanding perennials there are. The downside to flowering natives is putting up with slow top growth the first few years while their roots establish. But once mature, these survivors are rugged and long-lived. No watering, no fertilizing, no deadheading! And if the deer eat a few, it’s usually not the end of them.

As climate change kills off the weak and the delicate, natives point the way forward. They are not as flashy as what we’re used to, but we ignore them at our peril. After all, they’ve survived for eons on their own just fine so far. But which ones? Here are my suggestions.

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Best flowering nativars and similars for zone 6b — I’ve published articles on most of these plants individually, so I apologize if this section seems redundant. Still, it never hurts to mention the most reliable choices, just in case you’re looking for one or two you don’t have yet.

Click the links following each mention for in-depth information.

Monarda — Bee balm, Oswego tea, Monarda– whatever you call it, it is a lovely plant. Why not include both the wild form and a hybrid cultivar or two? Monarda’s only drawback is susceptibility to downy mildew, but many new varieties have solved that problem. More about monarda

Echinacea purpurea— I would be remiss if I didn’t mention coneflowers, the main player in many a natural garden. Some choices are hardier and more pollinator-friendly than others. Magnus is a robust nativar that bees and goldfinches adore. To extend the coneflower season, I recommend including a few hybrids. Many keep producing blooms in stunning colors well into October, after Magnus and others have gone to seed. Just be sure to include pollinator-friendly selections. More about coneflowers

Persicaria — Also called Mountain Fleece this plant is an underused “supporting player” for massing. Persicaria’s coarse foliage can look weedy out of bloom, but when planted with showier companions, persicaria contributes unrivaled texture and color over a long period. It sports exuberant red, pink or white “mini-wands” from midsummer to fall. In my garden the deer snack on the emerging foliage and budded tips early on, but once in bloom (if they leave enough buds) they let it alone. To discourage their browsing I no longer grow it, but wish I could.

Asclepsias incarnata –Swamp or rose milkweed fares better in my garden than common field milkweed because it’s more versatile in nearly every aspect than other milkweeds. It easily tolerates heat, rain, considerable shade and even high humidity while staying disease free. It also hosts monarchs and tussock moths just like any milkweed. Mine flower well even in half shade, a bonus if you have limited sun like I do. More about milkweeds

Veronicastrum virginicum — Known colloquially as Culver’s Root or Culverphysic, this tall beauty can be a devil to get started, but it’s lovely and tough once established. Start with plugs, don’t expect too much for a year or two, then enjoy the show once they start flowering. The light pink cultivar Erica is especially nice, with long-lasting, fluffy blooms. More about Culver’s Root

Rudbeckia hirta; Rudbeckia fulgida — Black-eyed Susans, brown-eyed Susans, we all know these cheerful gold-hued “daisies”. Hirta is an annual that reliably self-seeds; fulgida will live for several years, modestly reseeding to form dense colonies. These color machines are must-have perennials for the dog days of summer. More on rudbeckia

Tall Garden Phlox – No informal garden is complete without tall phlox. While not exactly native, these prodigious bloomers bring a lush look and often fragrance too. Most varieties on the market are hybrids these days, and nearly all are garden-worthy– take your pick. Delta Snow, shown here with deep lavender verbena bonariensis, is particularly disease-free and very floriferous. More about tall garden phlox

Agastache – Better known as hummingbird mint, this member of the hyssop family is under-utilized. Maybe that’s because most of the prettier hybrids are not reliably hardy in zone 6. I’ve found the best cultivar for southeastern Pennsylvania is Blue Fortune. It is a robust yet sparsely foliaged plant with real presence. Its lavender-blue flowers produce nectar over a very long period, making it popular with all the pollinators. If you want to grow hummingbird mint, start with Blue Fortune. Want a pink cultivar? Try Ava’s mint. More on Agastache

Helenium – Or sneezeweed as it’s often called, a misnomer since this lovely flower is not the cause of hay fever or allergies. Yellow, orange and red discs of two-toned petals surround bold buttons of gold and brown. Lovers of average to dry conditions, this frilly wheeled beauty blooms its head off from midsummer to late August. During wet spells, stake to prevent flopping. The red-orange cultivar Potters Wheel opens in July here, and is perhaps the easiest to find. Others available by mail order.

Japanese or fall Anemone – Anemones are certainly not native but are just as tough. Sometimes called wind flowers, these late summer and fall powerhouses of color really put on a show. When happy they can even be thuggish, so don’t put them where they might crowd out more delicate flowers over time. Japanese anemones are just glorious in August and September, lighting up the garden in a riot of color and motion. Bumblebees appreciate them too. More on fall anemones

Lilies – All lilies are attractive, but martagon and tiger lilies are tailor-made for informal gardens: they are deer-resistant, reliable, beautiful, long-blooming and very hardy. Their graceful candelabra forms also look better visually in an informal setting than fancier hybrids. I especially like the tiger lily hybrid Flore Pleno, a double, which the bees are still able to access despite its distorted petals. The color is a deep cool coral, which coordinates especially nicely with other colors. More about true lilies

Echinops – We know it as globe thistle; this bee magnet sports spiky gray-blue or silvery balls atop rather prickly foliage — it is a thistle, after all! Prized for its fun shape and strong architectural presence, this easy perennial will take care of itself. (Gloves are a must when handling.) It gets quite tall, so put it with grasses or similar sized companions. A good alternative to rattlesnake master, or plant the latter at its feet!

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Below is a roundup of photos of my north bank garden in high summer. Supporting cast members not mentioned above include drumstick allium, fleabane, daylilies, orlaya, cleome, Queen Ann’s Lace, toadflax, joe pyeweed, peonies, yarrow and verbena.

What will your garden look like in high summer? Plan it now!