Eleven Garden Giants
By Colleen O'Neill Nice
I love a soft, cool rain. My gardens love it too. But not all plants flourish in a wet sunless environment. So, when strolling through my woodland borders, I was captivated by the giants of the garden who absolutely thrived in all the rain. While many gardeners were complaining about powdery mildew on their peonies and leaf spot on their zinnias, I was frolicking amongst my mammoth monsters that seemed to grow overnight. Given ample room and moist conditions, these prodigious perennials created a tropical effect, adding drama with a frenzy of foliage.
Arching over the pulmonaria and hosta,the thick stems of Astilboides tabularis (formerly known as Rodgersia tabularis) support huge shield-like leaves. The bright green leaf surface has a sandpaper texture with numerous small teeth projecting from the undulating leaf margins. In addition to the
strikingly bold foliage, creamywhite panicles rise upward in July, on tall stems. A single specimen
can reach three to four feet in height and width, so ample room should be allowed when siting this plant. Astilboides is a low maintenance, clump-forming perennial that prefers cool, moist soil in partial shade. It can be divided in the spring, as the foliage emerges, or propagated from seed in the fall.
I use the handsome large-leafed Rodgersia aesculifolia in my garden to help camouflage the gap left by my bleeding hearts after they go dormant for the summer. This rodgersia has palmate leaves that resemble those of a horse chestnut. Each leaflet is coursely toothed, strongly textured and about seven inches long. In July, white flowers bloom on upright, two-foot tall stems, while the overall height of the plant can reach four feet. Rodgersias prefer morning sun and moist soil with plenty of organic matter. Finely-textured plants like ferns, corydalis or astilbe are a suitable contrast for the robust foliage of this perennial. Propagate rodgersia by division in early spring or by starting seeds
in a cold frame.
Hosta ‘Big Daddy’ is a real showstopper and gets plenty of attention in my garden. The enormous frosty blue leaves are cupped and thickly quilted, so slugs are not a threat. In July, white bell-shaped flowers poke up through the foliage. Like most hostas, ‘Big Daddy’ prefers partial to full shade and regular watering. It grows about three feet tall and four feet wide, shading out weeds as it matures. It is a tough plant and tolerates drought as well as sandy or clay soils. I prefer to divide ‘Big Daddy’ in the spring before foliage emerges, but fall division works as well. In October, I delight in collecting ripe seeds from Big Daddy’ which are always quick to germinate. Since hosta seeds do not usually come true to the parent, I often get a mix of blue, green and gold babies. The grey-blue foliage of this specimen is a great companion for my finely dissected red-leafed Japanese Maple.
Often called the umbrella plant, Darmera peltata thrives on moisture. Pink flowers emerge in early spring from leafless, hairy stems. As theflowers fade, enormous, upswept, umbrella-like foliage enlarges up to 24” across. The dark green leaves are rounded, deeply lobed and toothed, with
conspicuous veining. The vase-shaped clump, four feet tall by three feet wide, can be divided
in spring or fall. A fast grower, it needs constant moisture in a part to full shade setting. A native of the western U.S., darmera is hardy in zones 5-7, and creates a distinct, fresh look in my woodland border.
Romping through my garden is the infamous Petasites japonicus ‘Variegata’ or giant Japanese butterbur (I call it dinosaur food, for short). Its large green flowers bloom close to the ground in
early spring, with leaves appearing soon after. I often caution people about this plant before they put it in their gardens, but no one ever heeds my warnings.The three to four foot wide leaves, covered with brushstrokes of pale yellow, cream and green, are just too seducing to pass up. This giant can be
very aggressive, traveling by undergroundrope-like rhizomes, pushing its way through plant roots just to get closer to a sprinkler head. It is by no means low maintenance if planted amongst other more polite perennials. Once or twice a season, I thin out petacites to give its neighbors – ferns, hostas, baneberry and dicentra – a fighting chance. Hardy in zones 5 to 9, it can reach three to four feet tall in wet summers. You probably won’t need to propagate more of this plant, but just in case, two-inch rhizome sections will sprout into new plants. The stalks and flower buds are edible.
A noteworthy complement to Hosta ‘Big Daddy’ is Hosta ‘Sagae’ with its frosted blue-green leaves
edged in yellow. Grey-green streaks are painted in the areas between the leaf’s center and its margins. The impressive upright mound consists of thick, triangular, slug-resistant foliage. In midsummer, lavender flowers rise up on four foot tallscapes. ‘Sagae’ grows three feet tall and five feet wide in rich, consistently moist soil. It prefers light sun to full shadewith leaf margins fading to cream in the sun. It grows very deep roots, so plant it in a good location and leave it alone for few years so it can reach its mature size.
For a strong vertical accent, Dryopteris tokyoensis is a perfect addition to the shade garden. The Tokyo wood fern's ladderlike, upright fronds form vase-shaped clumps that grow to four feet tall
in moist soil. It is a low maintenance, moderate grower that prefers light to full shadein a sheltered habitat. This easy-to-grow, relatively unknown, deciduous fern from Japan is hardy in zones 4-9. It is easily propagated from ripe spores or divided in the spring or fall. It is truly impressive arching over hostas, begonias or dicentra.
My favorite large hosta for dividing areas in my garden is Hosta ‘Nigrescens’. Its immense, grey-green leaves form a very upright vase shape and several plants spaced out in a row can create a hedge effect. Its broad, cupped and corrugated foliage is thick and slug resistant. In August, pale lavender flowers can reach seven to eight feet, one of the tallest scapes of any hosta. Hardy inzones 3-8, ‘Nigrescens’ needs to be watered regularly in a partial to full shade environment. At maturity, it can grow three feet tall by six feet wide. For seed propagation, allow pods to dry on the plant, then break open the pods to collect the seeds.
The largest of the northeastern native wood ferns, Dryopteris ‘Goldiana’ (Goldie's Wood Fern) reaches
four feet tall in ideal conditions. It is a bold, somewhat coarse fern, forming large clusters of graceful
arching fronds. Broad, oblong-triangular foliage arises from a vase-like clump that spreads slowly by creeping rhizomes. Named for Scottish botanist John Goldie, its fronds are green without a hint of gold. This easy-to-grow deciduous fern prefers a dappled shady moisture-retentive woodland site.
It is hardy in zones 3-8 and is very attractive planted in masses where strong, bold texture is desired.
Symphytum officinale is a colossal, perennial herb which is a particularly valuable source of fertility for the organic gardener. Also known as comfrey, its very deep roots mine a variety of nutrients from the soil. The nutrients are then made available through its large, fast growing leaves which quickly
break down into a thick black liquid. The leaves of comfrey contain 2-3 times more potassium than farmyard manure. Comfrey can be used as a compost activator, a liquid fertilizer, a side dressing or added directly to your potting soil. It grows two to three feet tall and four to five feet wide in full sun and is hardy in zones 4-9. Tiny purple flowers in summer are an added bonus. I usually harvest the large, arrow-shaped leaves several times throughout the season and add them to my compost heaps. Propagate from seed or division.
Lastly, the sinister Dracunculus vulgaris (Dragon Arum) is the ultimate extreme plant reaching
three to five feet tall. A snake-skin patterned, thick stem emerges from the soil in spring with sickle-shaped dragon’s claw foliage. In early summer, a striking upward thrusting spathe surrounds an 18-inch spadix which mimics both the color and smell of rotting meat. The odor attracts the flies that are its pollinators and luckily, lasts only a day. The inflorescence persists for almost a week. Need I say that proper siting of this plant is essential. Hardy in zones 5-9, dragon arum prefers moist conditions in sun or bright shade. Propagate fresh seeds or divide in autumn.
By selecting a variety of different plants for your garden, you can attain both interest and drama, no matter what the weather brings. Consider planting a few moisture-loving divas in large pots as well. Be sure they have good drainage and a thick top-dressing of mulch to help maintain moisture. And then, let it rain, let it rain, let it rain.
Printed in the Upstate Gardeners’ Journal, May-June 2010