I'd like to plant a perennial garden and I want as much flower as possible. Color all summer. What's your recipe for making good perennial combinations? – K. R. -
We say to curb the headlong rush for flowers. Focus there and leaves are too often left behind. You will do yourself and your garden a favor if you focus on elegant foliage, whether you are planning a new bed or re-mixing existing plants. Choose and place the plants for foliage and form first, and take the flowers as a bonus.
Here's how we designed a perennial bed that will be a pleasure to view from April well into October. It's all built on great foliage, pivoting around one plant's big, dramatic leaves.
The great mix begins at the garden center
At a garden center recently, we indulged in a car-load of hardy, zone 5 perennials for a newly-cleared 6' x 8' space in our garden. Before going through the check-out, we took a minute to arrange the new acquisitions as if they were planted in one large container. This made it evident that the mix contained an abundance of fine-textured (small-leaf) plants. We needed to add one coarse-textured plant to give us a contrasting focal point to work with.
Wanted: Rhubarb in the lead role
Ornamental rhubarb (species such as Rheum palmatum) came to mind. Related to cooking rhubarb (an ancient hybrid, R. x cultorum), the ornamental species are grown for looks rather than for making tart pies. Although both cooking and looking rhubarbs are good for dramatic effects based on coarse foliage, an ornamental variety such as 'Atropurpureum,' 'Red Select,' or 'Bowles Crimson' is better where the gardener wants more red in foliage or flower.
It was no surprise that ornamental rhubarb wasn't in stock at the garden center. The best designs seem to include at least one hard-to-find item. The last time we needed ornamental rhubarb it came by mail from a specialty nursery. This time, unwilling to wait and lacking time to shop other local sources, we decided to substitute.
Stand-in for the star
What would work was an alternate sun-loving plant with bold foliage. Colewort (Crambe
cordifolia) was a perfect fit. Like rhubarb, it needs a square yard of elbow room at ground level and its huge, crinkly, wavy edge leaves are borne low to the ground.Colewort in bloom, however, is quite unlike rhubarb. Rhubarb sends up 4' to 6' spires, tips densely packed with cream- or dull red florets, while colewort has honey-scented white flowers in an airy spray 6' tall and 4' wide. For a few weeks in June, these blossoms upstage the foliage and turn colewort into a giant baby's breath.
Admire the bloom but make it bow out at end of its act
Admire this bloom and fragrance but cut the stalks down before seed can ripen in late July. This refocuses the spotlight on the foliage, returns the plant to a size more suitable for the average garden, and eliminates the tedious job of weeding out hundreds of volunteer seedlings.
The drawing hows how colewort will occupy a space in this bed where it can "show off" among plants with smaller leaves. In that arrangement, the colewort will be "framed" with lacy, ferny leaves and its curvaceous outline will be flanked with a complement of vertical-form plants. After those main players were placed, we spiced the concoction with species whose main contributions are flowers to fill critical gaps in the bloom sequence.
This diagram, called a plan view of the garden, indicates where to place each plant in a rectangle six feet deep and eight feet wide. Placed as indicated in the diagram, the combination will look like the drawing at the beginning of this article.
The overall visual concept of this garden:
The "star" player is coarse-textured colewort.
Circular gray symbols (2, 3, 4, 5, 7) are plants to make a ferny frame around the star.
Rectangular gray symbols (6, 8, 9,10) are vertical accent plants.
Dashed lines indicate positions where more than one of the numbered plant can be placed. Alternately, the plant can be allowed to grow for a season or two, then divided to fill all of its numbered spaces.
At the focal point is the "star":
1 - Colewort (Crambe cordifolia CRAM-bay cor-dih-FOE-lee-uh), a 24" mound of big, dark green leaves. Topped in June with white fragrant flowers on leafless stalks up to 6' tall.
Creating a ferny, fine-textured frame (gray, circular symbols):
2 - Dwarf delphinium (Delphinium grandiflorum 'Butterfly Blue' or 'Butterfly Compactum',
dell-FIN-ee-um grand-ih-FLOR-um), 24" stalks with dark blue flowers above dissected leaves, blooms mid-June to late July.
3 - Silver Brocade beach wormwood (Artemisia stelleriana 'Silver Brocade', ar-teh-MEEZ-eeuh stell-LAR-ee-ah-na), An aptly-named 18" mound of grey foliage.
4 - Blue corydalis (Corydalis flexuosa 'Blue Panda' or 'China Blue', coh-RID-uh-liss flex-yew-OH-suh), 12" tall, blue-green mound spangled with smoky blue flowers from mid-May to late June.
5 - Arkansas blue star (Amsonia hubrechtii, am-SO-nee-uh hew-BRECK-tee-eye), 30" tall. Bottlebrush foliage with domed clusters of steely blue flowers from late May into June.
Vertical accents (gray, square symbols):
6 - Siberian iris (Iris sibirica 'Caesar's Brother', EYE-ris sy-BEER-ih-cuh), narrow, 36" fountain of dark green grassy leaves and dark blue-violet flowers in early June. You may plant Siberian iris for its flower, but the garden comes to depend on its strong vertical lines.
7 - Boltonia (Boltonia asteroides, bowl-TOE-nee-uh as-ter-OY-dees), sturdy, no-stake, 5' column of light green foliage smothered in white or lilac, 1", daisy flowers in October.
8 - Hybrid goldenrod (Solidago 'Crown of Rays', sol-ih-DAY-goh), a stiff, 24" clump topped in August with bright yellow flowers in feather-duster sprays. Goldenrod's form and texture, while respectable, is not show-stopping. So it's placed simply to make the most of its late summer floral contribution.
Providing flower during gaps:
To bloom in gaps of this group's bloom sequence, and positioned so their come-and-go profiles blend smoothly with adjacent columnar plants (white, square symbols):
9 - Shasta daisy (Leucanthemum x superbum 'Thomas Killen', lew-CAN-thee-mum ex sue-PERbum), classic white discs on sturdy 30" stems from early to late July. In bloom, its profile is columnar. Many gardeners have a soft spot for Shasta daisy flowers. We take care to position the plant so its come-and-go foliage doesn't blight the late-summer scene.
10 - Foxtail lily (Eremerus isabellinus 'Shelford Hybrid', ur-REH-mur-ess iz-uh-bell-EYE-nus), a spray of knife-blade foliage 12-18" tall in early spring launches a 3-4' leafless spear topped in late May and early June with an impressive spike of yellow, orange, salmon, white or pink flowers. They're exclamation points in a spring garden, then they go dormant after bloom.
Symbols outlined with dashed lines
These indicate "future plants" -- where a single, original plant might be divided and
spread to make a larger mass in the future.
Download that shady plan offered at the top of this article. It features these plants:
At the focal point:
1 - Rodger's flower (Rodgersia pinnata rod-JER-see-ah pin-NAY-tuh), a 24" mound of big leaves divided into leaflets arranged like spokes, 36" flower stalk with a creamy white plume of flowers in June.
Creating a ferny, fine-textured frame:
2 - Japanese painted fern (Athyrium nipponicum 'Pictum', ah-THEER-ee-um nip-PON-ih-cum), 15" mound of delicate, sliver- and maroon-frosted fronds.
3 - Kabitan hosta (Hosta sieboldii 'Kabitan', HAHS-tuh see-BOWL-dee-eye), leaves are narrow, wavy-edged, gold with a dark green margin in a 8" mound, lilac flowers dangle from 20" flower stalks in August.
4 - Golden bleeding heart (Corydalis lutea, coh-RID-uh-liss LEW-tee-uh), ferny green foliage in a 15" mound, spangled with golden flowers May to July.
5 - Lavender mist meadow rue (Thalictrum rochebrunianum, tha-LIK-trum rock-brew-nee-AYnum) 4-5' column of foliage like dangling discs, topped with a cloud of tiny lilac flowers in July.
6 - Fall fairy candle or bugbane (Cimicifuga ramosa, sim-ee-SIF-yew-guh rah-MOW-suh) ferny foliage in a 2-3' mound, topped by late summer with 4-6' flower stalks that open to white bottlebrush flowers in September or October.
7 - Turtlehead (Chelone species, key-LOW-nee), sturdy, no-stake, 36" stems with stiff, dark green leaves. Pink flowers like turtles' heads open in spikes in late July to mid-August.
8 - Variegated Solomon's seal (Polygonatum odoratum 'Variegatum', poh-lig-oh-NAY-tum ohdoh-RAY-tum), 18" tall, with white May flowers in paired lines below the arching stems. Leaves have a delicate white edge.
Providing flower during critical periods:
Again, these plants that provided needed flower color are also positioned so their come-and-go profiles blend smoothly with adjacent columnar plants:
9 - Toadlily (Tricyrtis hirta, try-SIR-tiss HER-tuh), 30" arching stems bear orchid-like lavender flowers in October.
10 - Blue bush clematis (Clematis heracleifolia, CLEM-ah-tis heh-RAH-clee-ih-FOH-leeah), 30", needs staking to maintain its columnar shape. Light blue, tube-shaped, 1" fragrant flowers open in August.