Gardens of endless possibility

Fresh, innovative container design often begins with a single plant and the many possibilities presented by its unique texture, form or colour.

Consider, for example, Heuchera Forever Purple. A zone 4 perennial, this Coral Bells variety boasts ultra-purple glossy leaves with fluted edges and short sprays of purple-pink flowers. Since it is key to combine a coarse-textured plant with one that is fine or delicately textured, Forever Purple might inspire a pairing with Meteor Shower Verbena bonariensis. At 51 to 76 centimetres tall, Meteor Shower is an upright annual featuring small, rounded clusters of lilac purple flowers at the ends of sturdy stems with dark green, narrow leaves. It makes a delightful thriller in sunny to part-sun container gardens.

For a spiller, choose Sweet Caroline Bewitched After Midnight sweet potato vine. A new introduction with a more relaxed trailing habit than its predecessor Bewitched, After Midnight’s smooth, black-purple foliage has the distinctive palmate shape of a maple leaf. Alternatively, Nico plectranthus is a classic, vigorous Swedish ivy with dark green, rugose foliage, prominent purple veins and smoky purple undersides. If the container is large enough, both could be incorporated into the design.

As a finishing touch, weave in Star Dust Super Flash, a new densely flowered, fast-growing euphorbia with tiny, star-shaped white flowers. The resulting combination would be a harmonious part-sun to part-shade arrangement.

Of course, heuchera varieties — with their many different colours — inspire endless plant combinations. What’s important is to strive for an arrangement that includes a variety of shapes, colours, sizes and textures. Achieving this goal is made easier by incorporating foliage plants and perennials into your container garden. In the fall, hardy or borderline-hardy perennials can be transplanted into the ground.

Deanna Cram, greenhouse manager at Shelmerdine Garden Centre, loves to include monarda, a hardy zone 3 perennial, in container designs. Even when the bright, spiky blooms of monarda — also known as bee balm or bergamot — aren’t in bloom, the foliage is wonderfully aromatic. Another perennial favourite for a container design is catmint (nepeta), which Cram recommends for its long season of bloom that ranges from June to early fall.

Choose from a number of cultivars, including Dropmore Blue, Walker’s Low, Junior Walker and Purrsian Blue. While size varies, each of these selections has dense, fragrant grey-green foliage and clusters of lavender blue flowers with dark purple calyxes. Purrsian Blue (Nepeta faassenii), hardy to zone 3, is an improved hybrid with a tidy, compact habit that makes it ideal for sunny borders and containers. In addition to attracting pollinators, nepeta’s aroma also attracts cats when its stems are broken. Cats are more likely to resist rolling around in nepeta when it is grown in a container.

Nepeta prefers full sun exposure. It thrives in soil that is not overly rich or moist. After the first flush of bloom, shear the stems back by one-half to promote rebloom.

Interestingly, Cram says that lupine is a fabulous perennial for growing in containers. Why? "Lupine has a reputation for not responding well to soil conditions that are too wet or too dry," Cram says.

"By growing lupine in containers, it’s possible to control the amount of water that the plant receives."

In addition to a preference for well-drained soil, lupines are inclined to grow more readily in acidic soil than our heavy clay soil. Most commercial potting mixes contain sphagnum peat moss, which is naturally very acidic.

Hardy to zone 3, lupines are tolerant of light shade. The showy, gorgeous flower spikes come in a range of colours, including blue, pink, rose, red, white and yellow. "Even when the flower is not in bloom," Cram says, "the added texture of the palmate foliage provides greater detail and impact in your container design."

Cram also suggests growing liatris, another hardy perennial, in containers. With a tall, upright habit that lends itself perfectly to the role of thriller in a container, liatris, also known as blazing star, has an abundance of narrow, green leaves that travel up and down its sturdy stem. The purple or white-flowered spikes resemble a bottle-brush so add unique texture and form to a container arrangement.

Summer’s extreme heat and dry conditions can be challenging for flowering annuals, especially in hardscaping areas such as patios or concrete balconies that absorb heat during the day. Golden Sword yucca, hardy to zone 4, basks in a full-sun location. It’s boldly striped green and creamy yellow sword-like leaves make a dramatic statement. Picture this variegated yucca in a low-profile container perched on an elegant pedestal.

Suited to going solo, Golden Sword yucca also combines well with other drought tolerant plants such as trailing Silver Falls Dichondra or the silver-white licorice plant (Helichrysum petiolare). For contrast and a floral element, underplant with a low-maintenance annual such as portulaca.

This spring, Schriemer’s Greenhouses in tSpringfield and Morden Nurseries are carrying the new Portulaca Cupcake series. Primed for record-breaking heat, Cupcake Cherry Baby and Cupcake Yellow Chrome are prolific bloomers with strong branching and long flowering periods.

For shade containers, perennials such as hostas provide coarse texture and unusual variegation. Ferns, too, add a light, airy texture to container designs. Harry Schriemer, owner of Grö Greenhouses, celebrating its second year at its new location on St. Anne’s Road, recommends tatting fern (Athyrium filix-femina Frizelliae) for its long fronds that have ball-like pinnae along their midribs, resembling a string of beads. A dwarf variety, tatting fern is hardy to zone 4. Maidenhair fern, too, with its delicate, fan-shaped fronds and shiny, black stems offers textural interest in a shade container.

Aralia cordata Sun King (commonly known as Japanese Spikenard) is a colourful foliage addition to shade containers. Reliably hardy to zone 3, Sun King’s foliage is chartreuse to lime green in colour when grown in full shade. In a brighter location where it receives a few hours of sun daily, the foliage takes on more of a golden-yellow tinge. Sun King’s finely veined leaves have serrated edges and distinctly pointy tips.

As a mature perennial, Sun King grows to 90 cm tall and wide. Fast growing, it maintains a manageable size when used in a container garden. When transplanting container-grown perennials into the garden in the fall, be sure to cease all fertilizing after the end of July.

T Rex begonias are dramatic, large-leaved annuals that provide some of the most unique colours, patterns and textures in all-foliage container gardens designed for deepest shade. Breeders are introducing more and more new varieties each spring. Significantly, T Rex begonias, once established, tolerate temperatures as cool as three degrees Celsius, ensuring a long-lasting container display well into fall. A recent introduction, T Rex First Blush is silvery lavender with a blush of raspberry and has a striking chocolate-brown pattern in the centre of the leaf.

The Jurassic series of begonias also provide dramatic foliage shapes and colours in shade containers. A notable example, Jurassic Green Streak Rex Begonia has silver-green leaves with dark green veins and a splash of rose in the middle of each leaf.

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