Sometimes, you need something big in the garden. Usually, gardeners fill large spaces with trees or shrubs. But sometimes that does not work. Say you have a large island bed in the middle of a big open space, and you want color most of the season, but you want it to have the potential to be removed if you want to turn it to lawn? That is when big perennials come into place. They fill a need when you were not sure of the need.
But what are considered big perennials? I would consider any perennial plant (those that die back to the ground each season) that is between 4 to 12 feet tall and 3 and 8 feet wide to be a big perennial. We have a lot of perennials with that stature, and indeed, many of they can reach height of 8 feet tall. And I do not know why, but most of them are natives. I suppose old world plants have been tamed for too long.
Out in the Sun
Planting in full sun conditions can be tricky for all of us. We need to think about plants that not only are tough, but drought resilient. A lot of our perennials, especially natives, prefer part sun, more than full. Full sun is 8 plus hours, while part sun is 4 to 8 hours. Shade is usually considered 6 hours or less of direct sunlight. It can get hot out there, especially in later summer. So we pick heat and drought tough plants.
One thing I have noticed over the years is that areas in full sun planted in mulch or no mulch do much better than those in rock. And they do even better if plant spacing is less considered. Plants like to have community around them. They like to share their roots with their neighbors, and with the mycorrhizal fungal network in the soil. And by sharing roots and fungal hyphae, plants become more drought resistant.
Locations for Big Perennials
I already mentioned planting in a large island bed, but what other places can big perennials go? There are a lot more spots than you might think. If you are re-imagining the perennial border, you might fill the back of it with big perennials. Other areas might include a large bed with a south or west facing wall behind it, or around a gazebo, or any place where you need to fill in with large plantings.
Some large perennials are more water-loving, and so need to be planted in the right places. I would suggest a large bog garden or rain garden area.
The Big Perennials
Agastache ‘Blue Fortune’
One of my favorite plants, Agastache or hummingbird mint gets around 3 to 5 feet tall and up to 3 feet wide. Since its a member of the Mint Family, it has aromatic leaves and flowers, and has few pest problems. There are mint-loving moths of course, but rabbits and deer do not like it. The flowers are favored by a variety of bees and butterflies. Plant it alongside milkweeds, Heliopsis, Rudbeckia, and native grasses.
Baptisia Decadence Deluxe Series
The Decadence Deluxe Series by Proven Winners includes some of the larger and showier Baptisia available. I really love some of the colors of this series, and I know that more are likely to come. They can grow 4 to 5 feet tall by 5 feet wide. Baptisia are host plants for several moths and bumblebees pollinate them. Plant them singly, in masses, or alongside native grasses, asters, goldenrods, or milkweeds. Selections include:
- Pink Truffles
- Periwinkle Popsicle
- Pink Lemonade
- Blue Bubbly
Rattlesnake Master
One of my all-time favorite natives, these big perennials grows 3 to 6 feet tall at flowering and 3 to 4 feet wide. They will flop if they get too much water, so keep them on the dry side. Members of the Parsley Family, they have unique, umbel-style flower arrangement. The white flowers are attractive to a wide range of pollinators, including Monarch butterflies. Only a few moths and insects feed on the plant, but native bees do use the hollow stems for their larvae in the spring, on last-years stems. Plant it alongside native grasses, asters, goldenrods, Rudbeckias, or milkweeds.
Joe-Pye Weed
Referring to several species within the Genus Eutrochium, Joe-Pye Weed is most commonly associated with Eutrochium purpureum. Joe-Pye Weed grows 5 to 9 feet tall and 4 to 6 feet wide. It blooms with reddish-pink flowers in mid to late summer, for around 5 weeks. Joe-Pye Weed attracts large numbers of bees and butterflies, and has few pests. However, it does get top heavy if not cut back once in late spring, so plant it in masses, or along with native grasses, bonesets, milkweeds, Baptisia, or ironweed.
Queen of the Prairie
Also known as Meadowsweet, this beautiful prairie native, prefers slightly marshy or wet areas. My first encounter with it was at the Muscotah Marsh, a wetland habitat in Atchison County, KS. It grows 4 to 6 feet tall and can colonize a large area, with bright pink or pale pink flowers in early summer. It is considered deer-proof once established, and provides pollen for a wide range of insects. Plant it alongside swamp milkweed, Culver’s root, bulrushes, or blue vervain.
Tuberous Sunflower
Also called Jerusalem artichoke, this member of the Aster Family gets big! It has bright yellow flowers, 4 to 5 inches in diameter, which are favored by many bees. A tough plant, tuberous sunflower will grow in dry to drought stricken soils, and still grows 6 to 8 feet tall and wide. Its name comes from the edible tubers which are produced underground and taste similar to a bland potato when cooked. Yes, I have tried them. They are best fried in butter. The seeds are consumed by a number of birds in autumn, and several moths feed on the plant parts. Plant these big perennials with native grasses, ironweed, blue sage, goldenrods, or common milkweed.
Meadow Blazingstar
I love the variety in the blazingstars, or Liatris. These perennials are some of the best for various uses in the garden and the different species bloom in succession. Meadow blazingstar is the largest, growing 4 to 5 feet tall in a 2 to 3 foot wide clump. They do reseed easily, so put them in a meadow garden or somewhere where they can spread. Plant them alongside ironweed, common milkweed, greyhead coneflower, native grasses, or Baptisia.
Hardy Hibiscus
Most gardeners do not know that the cultivars of hardy hibiscus have been produced using native species. These plants can take both wet or dry conditions, so put them into a rain garden or meadow garden. Some of the cultivars can grow up to 10 feet tall and wide. I like to plant them alongside native grasses, milkweeds, Culver’s root, and/or cup plant (Silphium perfoliatum). Some cultivars include:
- Berry Awesome
- Cookies and Cream
- Candy Crush
- Holy Grail
- Spinderella
- Lilac Crush
- Perfect Storm
Giant Rudbeckia
Also known as giant coneflower, this eastern US native can grow up to 8 feet tall, with 1 foot long, silvery-gray green leaves. It does well in drought and full sun conditions and is a striking plant in the garden. Rising above the foliage, the stiff flower stalks produce 2 inch flowerheads which can bloom for 4 to 6 weeks. The flowers are attractive to several butterflies and other pollinators. But the silvery-cast of the leaves deter rabbits and deer. Plant giant Rudbeckia along with native grasses, Obedient plant, ironweed, blue sage, and/or goldenrods.
Cutleaf Coneflower
Another Rudbeckia (laciniata), this big perennial can take sun or part shade. I have often found it growing in riparian areas under part shade. However, in full sun it grows 6 to 8 feet tall and outward into a 4 foot wide clump. The flowers can be double or single, depending on the cultivar. It is easy to transplant and can be grown in a variety of garden styles. Plant cutleaf coneflower alongside native grasses, Baptisia, milkweeds, and/or goldenrods. Cultivars include:
- Goldquelle – a double flowered variety.
- Herbstonne
- Hortensia – another double-flower.
Cup Plant
Virtually unknown outside of native plant groups, this is one of the big perennials which needs water. Sure, it will take some drought, but it prefers to grow in slightly swampy or boggy areas, in full sun. Mine grows in the ditch by our house as well as around the water meter. The leaves will hold water after a storm or rain. It grows 4 to 8 feet tall and 3 feet wide, but reseeds easily. Birds eat the seeds in autumn, spreading them around. The flowers are visited by a number of pollinators, including several bee species. Plant cup plant along with Queen of the Prairie, Culver’s root, swamp milkweed, switchgrass, and/or Obedient plant.
Prairie Dock
Another large, sunflower look a like, prairie dock has large, coarse leaves which spread into a 4 to 5 foot wide clump, growing 2 feet tall. The flower spikes rise out in July, growing 6 to 12 feet above the foliage. The flowers on cup plant look like sunflowers, spreading 2 to 4 inches across. They are visited by a number of bees and butterflies, and the seeds are eaten by birds. Plant prairie dock with native grasses, common milkweed, blue sage, Baptisia, and giant coneflower.
Giant Goldenrod
This species of Solidago grows best in slightly moist areas such as ditches of rain gardens. It was one of the first goldenrods I identified when we moved to our house. Growing 6 to 8 feet tall in clumps 5 to 6 feet wide, it blazes boldly in the landscape. A LOT of pollinators visit the golden flowers in autumn. I like to mix it into the garden alongside asters, Baptisia, ironweed, native grasses, and purple coneflower.
New England Aster
Another wetland type of species, this aster prefers moderately wet soils, and can suffer in drought. I have seen it attacked by lacebugs and spider mites when stressed from lack of water. But in the right place, it grows 6 feet tall and forms and 5 foot wide clump. The blooms can be purple, pink, mauve, reddish, or even white, and attract a lot of pollinators in late summer through early fall. Put it in with giant goldenrod, cup plant, Culver’s root, Obedient plant, switchgrass, and/or swamp milkweed.
Western Ironweed
One of the most underused of the big perennials, western ironweed is deer and rabbit proof. Even cows will not eat it. But the plant grows 3 to 5 feet tall and 3 feet wide in a clump. It can be trimmed back by 1/3 in June to keep the height down in a landscape. If planted in a tidy garden, deadhead after flowering to prevent seeding out. Several bees and lots of butterflies flock to the purple flowers in July, August, and September. And the seeds are eaten by various birds. Western ironweed should be planted with native grasses, asters, goldenrods, blazingstars, and many other natives.
Conclusion
Big perennials need big spaces, but there are usually gardens for them. If you live with limited garden space, you may still be able to plant these along a fence or up against a wall, as long as you have enough light. And they are mostly native, so you can enjoy many pollinators among them all season long.
Happy planting!
