My lower back still protests when I recall digging my first deep border in heavy, cold clay. That was back in the mid-nineties, a time when I believed gardening was as simple as following a color chart.
I learned the hard way that plants do not read the picture tags attached to their nursery pots. In 1998, I managed to rot a prized collection of rare terrestrial orchids because I kept the soil like a sponge, misjudging their moisture needs.
Later, in 2005, I spent an entire summer trying to acclimatize moisture-loving tropical imports in a dry, wind-swept backyard. The leaves turned to brown parchment within a week, teaching me a harsh lesson about wind-shear and transpiration.
When you design the rear of a garden bed, you are dealing with the engine room of your display. These tall species must provide structure, survive summer storms without snapping, and mask the untidy habits of shorter plants in front of them.
They also undergo immense physical stress from wind, heavy rain, and gravity. Here are ten tall options for those rear spaces, along with the dirt, sweat, and hard realities of growing them successfully.
1. Delphinium (Delphinium elatum)
Let us start with the most demanding plant on the list. Delphiniums are notorious garden divas that require constant monitoring, staking, and protection from pests.
If you ignore them, a single summer thunderstorm will snap their hollow stems at the ground level. I have walked out after a midnight squall to find my entire blue border lying face-down in the mud.
To grow them, you must insert sturdy hazel twigs or metal support rings when the plants are still under two feet tall. They also demand rich, moist soil and a heavy feed of composted manure every spring.
Slugs will skeletonize the new shoots before they even break the surface in April. You will need to apply organic bait early or face empty, muddy patches where your blue spires should be.
2. Hollyhock (Alcea rosea)
Hollyhocks evoke images of old country lanes, but they carry a dark, ugly secret. That secret is rust, a fungal disease caused by Puccinia malvacearum.
By July, the lower leaves of almost every hollyhock look like they have been sprayed with orange battery acid. The leaves yellow, shrivel, and hang like dead rags along the base of the stalks.
The trick is to use their height for the back of the border where mid-height plants, like hardy geraniums or phlox, can hide the diseased lower foliage. According to plant health guidelines from the Royal Horticultural Society, you must strip away these infected leaves immediately and destroy them.
Despite this ugly habit, their towering biennial spikes are excellent for dry, sunny positions. They self-seed in concrete cracks, demonstrating a rugged survival instinct that puts pampered perennials to shame.
3. Joe-Pye Weed (Eutrochium purpureum)
If you have wet, heavy soil that turns to grease in spring, this is your plant. Joe-Pye Weed is a massive native perennial that easily reaches seven feet in a decent summer.
It produces huge, dusty-pink flower heads that smell faintly of vanilla when the afternoon sun hits them. My patch in August hums so loudly with bumblebees and hoverflies that you can hear it from the back porch.
However, do not plant this in dry sand. If the roots dry out, the leaves turn crisp and brown at the edges, and the plant will stunt dramatically.
It also needs space to spread. It forms a dense, woody crown over the years that requires a very sharp spade and a strong back to divide in autumn.
4. Culver’s Root (Veronicastrum virginicum)
For those who find delphiniums too high-maintenance, Culver’s Root is a reliable alternative. It produces elegant, candelabra-like spikes of white or pale blue flowers in midsummer.
I first saw this plant used effectively at the Royal Botanic Gardens, Kew, where it held its own against aggressive grasses. The stems are remarkably tough and rarely require staking, even in open, windy positions.
It prefers a moist, humus-rich soil in full sun to partial shade. If your soil is too dry, the lower leaves will drop, leaving bare stems that look untidy.
The flowers fade to attractive brown seed heads that persist through winter. I leave mine standing until February to give the goldfinches something to feed on during ice storms.
5. Autumn Sun Coneflower (Rudbeckia laciniata ‘Herbstsonne’)
This plant is a monster, easily reaching seven or eight feet in height. It features drooping, bright yellow petals around a prominent green central cone.
It spreads via tough, yellow rhizomes that will colonize a border if left unchecked. Every three years, I have to dig around the clump with a sharp spade, severing the outer runners to keep it from choking my phlox.
It is excellent for late summer color when other plants are looking worn out. The stems are thick, but the sheer weight of the flower heads can cause them to lean after heavy rain.
I recommend cutting the entire clump back by half in late May. This “Chelsea Chop” delays flowering by two weeks but results in shorter, self-supporting stems that do not flop.
6. Giant Meadow Rue (Thalictrum rochebruneanum)
This species offers a completely different texture for the back of your border. Instead of solid spires, it produces airy clouds of tiny lavender-purple flowers with yellow stamens.
It looks incredibly delicate, like a giant maidenhair fern, but the stems are surprisingly resilient. They sway in the wind rather than snapping, though they do need some protection from prevailing gales.
I learned to plant this in dappled shade where the delicate flowers do not bleach in the midday heat. It prefers cool, rich soil that does not dry out during the summer months.
During my trip to the Singapore Botanic Gardens, I observed how they utilized layered heights to create depth in tropical borders. I use this plant similarly in temperate zones, letting its translucent canopy float above solid green foliage.
7. Plume Poppy (Macleaya cordata)
I must offer a stern warning before you introduce this plant to your garden. The Plume Poppy is highly invasive in light, sandy soils due to its traveling underground runners.
I made the mistake of planting it in a client’s light loam years ago, and we spent three seasons digging up orange, rubbery roots from their lawn. However, if you have heavy clay or a restricted root run, it is a magnificent architectural specimen.
It features large, scalloped, grey-green leaves with white undersides that catch the wind. The flowers are tiny, buff-colored plumes that appear in late summer.
Keep it contained, or plant it in a spot where you can run over the stray shoots with a lawnmower. If you treat it with respect, it provides a dramatic, metallic backdrop that few other plants can match.
8. Monkshood (Aconitum napellus)
Monkshood provides rich, deep blue flowers in late summer when most blue-flowered plants have long since faded. It looks similar to delphinium but is far more tolerant of shade and wet soil.
However, you must respect its toxicity. Every part of this plant contains aconitine, a potent neurotoxin that can be absorbed through cuts in your skin.
I always wear thick rubber gloves when handling, dividing, or cutting back monkshood in autumn. Keep it away from vegetable plots where its fleshy roots could be mistaken for horseradish or parsnips.
If you have children or pets that chew on plants, cross this off your list immediately. For mature gardens, it remains a valuable, deer-resistant choice for damp, shady corners.
9. Willow-leaved Sunflower (Helianthus salicifolius)
This plant is grown primarily for its foliage rather than its flowers. It features thousands of narrow, weeping, willow-like leaves that cascade down six-foot stems, looking like miniature green fountains.
In late October, it produces small, bright yellow daisies at the very top of the stems. The flowers are almost an afterthought; the real value is the soft, fine-textured screen it provides all summer.
It is tough, drought-tolerant once established, and grows in almost any soil type. The main issue is its tendency to become top-heavy and lean at a forty-five-degree angle over your path.
I prune the growing tips twice in early summer to encourage branching. This keeps the height down to a manageable five feet and prevents the clump from collapsing under its own weight.
10. Common Foxglove (Digitalis purpurea)
The wild foxglove is a classic choice for the rear of a shady border. Its tall, spotted bells are highly attractive to bumblebees, which crawl deep inside the tubes to reach the nectar.
Remember that the common foxglove is a biennial. It spends its first year as a flat rosette of furry leaves, flowers in its second year, and then dies after shedding seed.
To keep a continuous display, you must let them self-seed or plant new specimens every autumn. The seedlings will pop up everywhere, requiring you to weed out the ones that choose inconvenient spots.
They prefer acid, moisture-retentive soil rich in leaf mold. According to data from the Missouri Botanical Garden, they perform best in partial shade, especially in regions with hot, dry summers.
The Reality of Maintaining Tall Borders
To keep these giants looking good, you must accept the physical labor involved. You will spend spring afternoons on your knees, pushing bamboo canes into heavy soil and tying green jute twine around emerging stems.
Your hands will get stained with orange sap from plume poppies or dirt from wet compost. You will feel the ache in your lower back after dragging heavy watering cans to thirsty Joe-Pye weeds during a July drought.
The hose will kink in the exact same spot it always does, splashing water down your boots while you try to wash off powdery mildew spores. Yet, when you look across the yard in late summer, and see those tall stems holding up their flowers against a clear sky, the frustration fades.
Gardening is not about instant, perfect pictures. It is about working alongside the slow, messy, and often unpredictable forces of nature to build something that lasts.