Garden centers offer many shorter, compact perennial choices these days for use in landscapes with limited gardening space. But if you have a spacious landscape, a meadow, or a “wild” garden, then taller, bulkier perennials may be more suitable choices. Read on as I illustrate this point by taking you for a quick tour of the taller perennials on my property.
THE ORIGINAL PLAN
When I designed the landscape for our home south of Charlottesville 13 years ago, I had four specific goals in mind for our treeless 3.5-acre lot: Install foundation plantings around our newly built house, plant a variety of trees and shrubs, develop a fairly large perennial garden, and install raised beds for a vegetable garden.
Those projects replaced some of the grass on our lot (which was previously a featureless cow pasture), but we still had a lot of grass left to mow. So, I decided to landscape the area adjacent to the 550-foot long plank fence that borders our back yard. Using the fence as a backdrop, I envisioned deep, 15’ to 20’ undulating beds filled with woody and herbaceous plants. A mixture of trees and shrubs (the “bones” of the garden) was installed first. Then, I planted drifts of yarrow, asters, hardy mums, and Rudbeckia among other perennials. Wild violets filled in some of the sunnier areas as a ground cover. Hardy geraniums, Tiarella, and wild ginger served as ground covers in another, partly shady area. Eventually, the perennials began to fill the spaces between the trees and shrubs, and all was well – for a time.
THE PLAN GOES AWRY
As the landscape plantings matured, I saw that too many of my original perennial plant choices were mound shaped. That made the design look monotonous. Also, some grew too low to the ground (1.5’ to 2’ on average), making them difficult to see from a distance. That’s when I realized the design needed tweaking. It needed additional plants that would:
- Fill the void between the lower-growing perennials and the trees and shrubs that had grown much taller.
- Be clearly visible from our house, which is about 180′ from the fence.
- Provide vertical elements to contrast with all the lower, mound-shaped forms.
- Be pollinator friendly and provide habitat for wildlife species.
- Fill in large areas over time as a lawn replacement.
GETTING STARTED WITH TALL PERENNIALS
More shrubs would not have solved this problem. They would have been too heavy, too dominant. The design needed a “lighter” touch, which is why I chose tall perennials of 4’ or more to provide a more naturalistic, layered look.
So, my experiment with tall perennials began with grasses. Starting with groups of ‘Karl Foerster’ feather reed grasses (Calamagrostis x acutiflora) (4’ tall by 2’ wide), I noticed how the feathery seed heads in mid-summer stretched higher than the top fence rail and added an interesting softening contrast with the solid boards on the fence. ‘Apache Rose’ Switch grasses (Panicum virgatum) (4’ tall by 2.5’ wide) added additional height and pleasing texture from late summer all the way through the winter months. So far, so good.
In addition to these two grasses, I gradually added a variety of other tall perennials, such as:
False Aster (Boltonia asteroides) – Due to its relaxed habit, this 5’ to 6’ tall by 4’ wide perennial is well suited for an informal cottage or “wild” garden setting. I became interested in Boltonia years ago at a friend’s house where I saw the plant gently cascading over a stone wall in late summer. It was covered in a billowing mass of 1” white blossoms with yellow centers. Because it does tend to be floppy, it should be cut back by about a third in May or June to stimulate a bushier, more compact habit. Otherwise, it may need to be staked. I grow the straight species, but most sources recommend ‘Snowbank’, a shorter, better-behaved cultivar.
Joe Pye Weed (Eutrochium fistulosum) – This 7’ tall native is often seen growing along roadsides all over the east coast. As a host plant for a variety of bee, butterfly, and moth species, Joe Pye Weed is well regarded as a good nectar plant for visiting pollinator species. The mauve-pink flower clusters appear in July, when there’s not much else going on in the garden. The plant can be cut back by half in early June to control its height. Alternatively, check out one of the “dwarf” cultivars such as Baby Joe (4’ tall) or Gateway (4’ to 6’ tall).
False Blue Indigo (Baptisia australis) – Most sources say this plant grows between 3’ and 4’ tall and 4’ wide, but when in flower, it tops out at more than 4’ in my garden. I am aware that some hybridized varieties such as ‘Purple Smoke’ can top out at 5’. I love this plant because the vertical spikes of stunning lavender-blue flowers can easily be seen from a distance in my landscape. After it finishes blooming in spring, it tends to flop over a bit, probably because of the weight of the seed pods. However, shearing it back by a third removes the seed pods and solves the flopping problem.
Common Milkweed (Asclepias syriaca) – Having grown up on a farm where this large, coarse-looking plant was an agricultural pest, I am not a big fan of it. However, common milkweed is a critical host plant for Monarch butterfly larvae as well as an important host for other species such as those listed in the U.S. Fish and Wildlife’s blog on Milkweed – For More than Monarch Butterflies. For this reason, I do grow it in my landscape where it tops out at nearly 7’. It can spread aggressively into large colonies. So, I am watching it to make sure it doesn’t get out of control.
Culver’s Root (Veronicastrum virginicum) – This 4’ to 6’ tall by 4’ wide plant provides a good strong vertical contrast to all the mound-shaped plants in my garden. The flowers appear as 6” to 9” long racemes (spikes) in mid-summer and last for about 4 to 6 weeks. After it finishes blooming, it can be cut back hard, which encourages it to generate fresh new growth. A few cultivars of this plant are available displaying pale lavender or pinkish flowers, but I prefer the straight species, with its white flowers.
Cup Plant (Silphium perfoliatum) – Whether you call it cup plant, Indian cup plant, or rosinweed, this 4’ to 6’ tall plant makes a bold statement in the mixed border. It has attractive large leaves, strong stalks, and 3” to 4” yellow, sunflower-like blossoms in mid- to late summer. Although native and therefore not technically invasive, this clump-forming plant can spread aggressively. I have plenty of room for it in my mixed border, but I keep it deadheaded so that it doesn’t seed where it’s not wanted.
Cutleaf Coneflower (Rudbeckia laciniata) ‘Herbstsonne’ — ‘Herbstsonne’, which translates to ‘Autumn sun’, is a favorite cultivar of cutleaf coneflower. In the third edition of his reference book on Herbaceous Perennial Plants, author Allan Armitage refers to ‘Herbstsonne’ as “one of the finest coneflowers in cultivation” and “…the king of the sunny fall garden.” As the name suggests, the blossoms on this 5’ to 7’ tall by 4’ wide perennial are a strong yellow color with green cones. The flowering period generally lasts from August through October. If this plant grows taller than you would like, it responds well to being cut back to a leaf node lower on the stem. I have sometimes cut it back twice during the growing season – once in May and again in June or early July – to control its height.
Perennial Sunflower (Helianthus laetiflorus ‘Lemon queen’) – While there are other perennial Helianthus species that are more appealing, this natural hybrid of two perennial species happens to be the one I bought at a local plant sale some years ago. I was attracted to the idea of having hundreds of yellow blossoms in mid-summer when my garden normally goes on a break. It easily tops out between 5’ and 7’ and is perfect for the back of the border. It does, however, spread with wild abandon (translation: it is aggressive!). When it grows out of its allotted space, it’s very easy to pull up. It more than makes up for its aggressiveness when it starts blooming in July and is covered with butterflies.
Tall Coreopsis (C. tripteris) – This species tops out at between 7’ and 9’ and is a giant compared to shorter, 1’ to 2’ varieties such as lanceleaf (C. lanceolata) or threadleaf (C. verticillata). Tall Coreopsis has a long bloom time starting in late July and lasting for about two months. When in bloom, the numbers of insects attracted to it are unbelievable. Various pollinator species flock to the bright yellow flowers and goldfinches love its seeds. I grow ‘Gold Standard’, a 5’ to 6’ tall cultivar that is shorter than the straight species. According to the Mt. Cuba Center plant trial information, ‘Gold Standard’ has strong stems that never flop and is sturdier than the straight species.
GENERAL OBSERVATIONS ABOUT TALL PERENNIALS
Before introducing any new plant to your garden, research it thoroughly to make sure you know what you are getting into. For example, make sure you know how large the plant will be after it’s been in the ground for several years. Some of these taller perennials may spread well beyond the space allocated to them. That may be beneficial if, like me, you want plants that can eventually fill in a larger area. But if you’re concerned that a plant may spread too aggressively in your landscape, then opt for other, “better behaved” species more suitable for your needs.
Keep in mind what the plant will look like throughout the growing season. In his book New Naturalism, author Kelly Norris advises us that: “It’s easy to lean heavily on the later lushness of tall perennials, which form a green umbrella of vegetation over the ground, but these don’t jump to life in the first two weeks of spring.” In other words, many of these plants don’t offer any clues as to their final size when they are just emerging in spring, so it can be a shock when they reach their full height and width later in the growing season and tower over your other plantings.
If you want to add taller perennials to your own landscape, then choose a plant height that makes sense for you. In my landscape, tall perennials of at least 4’ or more made sense because of the height of the plank fence behind the plantings plus the size and shape of plantings already in place. But that may be too tall for some landscapes. Fortunately, many excellent shorter perennial species fall within the 3’ to 4’ tall range, such as gayfeather (Liatris Spicata), some beebalm (Monarda) varieties, and purple coneflower (Echinacea purpurea).
IN SUMMARY
My landscape continues to be a work in progress. There’s still a lot of work to be done, but the tall perennials I’ve added so far make the entire fencerow look much more interesting. It’s a little wilder looking now, but it’s a look I can live with. I’m also pleased that the plants are providing pollen and nectar for beneficial insect species as well as nesting material and habitat for the many birds, small mammals, and amphibians that visit my back yard.
FEATURE PHOTO: Pat Chadwick
SOURCES
Armitage’s Native Plants for North American Gardens (Armitage, Allan M., 2006)
Herbaceous Perennial Plants, 3rd Edition (Armitage, Allan M., 2008)
Native Plants of the Southeast, A Comprehensive Guide to the Best 460 Species for the Garden (Mellichamp, Larry, 2014)
New Naturalism (Norris, Kelly D., 2021)
Tall Perennials, Larger-than-Life Plants for Gardens of All Sizes (Turner, Roger, 2009)
