“Pteridophyllum racemosum," I answered, thereby landing a privileged internship at New York's Stonecrop Gardens. My bottomless appreciation for woodland plants, of which the said Pteridophyllum is an uncommon example, has always paid off. Obscure or mainstream, as subtle as moss or as beefy as a giant hosta, forest-dwelling plants abound. Nowadays, as an urban landscape designer stuck with shady conditions over shadier conditions, I strive to vary my plant palette as much as possible. For this I sometimes rely on choice, slow-growing and hard-to-get herbaceous treasures. CYAN Horticulture Japanese Glaucidium
(Glaucidium palmatum)

Amateur peony growers and aficionados of rodgersias will find common ground in the Japanese Glaucidium (Glaucidium palmatum). At ease in any humus-rich, cool woodland, Glaucidium offers both foliar and floral appeal, with sort of fat maple leaves and large, stripped-down pink corollas. It comes in white, too. Slow yet hardy, hard to find yet reliable, Glaucidium is the perfect choice for dedicated sedentary gardeners.

USDA zones: 3 to 8
Water requirement: Moist soil
Light requirement: Partial to dappled shade
Mature size: 2 1/2 tall and wide
Seasonal interest: Early summer
When to plant: Anytime CYAN Horticulture Willow Gentian
(Gentiana asclepiadea)

If anything must be blamed for the rarity of the willow-leaved gentian (Gentiana asclepiadea), it is its painfully slow growth habit. Otherwise, nothing's difficult about it: Dappled shade is preferred; so is a rich and moist soil. Once established, this gentian grows up and then gracefully arches out into a striking fountain of solid blue trumpet flowers. A mid- to late-summer bloomer, it fits east-facing borders as well as light woodlands.

USDA zones: 4 to 8 (find your zone)
Water requirement: Moist soil
Light requirement: Partial to dappled shade
Mature size: 1 1/2 feet tall and 2 1/2 feet wide
Seasonal interest: Summer
When to plant: Anytime CYAN Horticulture Japanese anemonopsis
(Anemonopsis macrophylla)

Even rarer and just as desirable is the Japanese anemonopsis (Anemonopsis macrophylla). With healthy foliage resembling that of green bugbane, anemonopsis deploys ethereal sprays of nodding pink bells, rounded and waxy. The spectacle is breathtaking, especially when seen from the side (as is the case on plants grown on a hillside, like in this example in Charlevoix, Quebec).

USDA zones: 4 to 8
Water requirement: Moist soil
Light requirement: Partial to dappled shade
Mature size: 3 feet tall and 2 1/2 feet wide
Seasonal interest: Summer
When to plant: Anytime CYAN Horticulture Umbrella Leaf
(Diphylleia cymosa)

Trading finesse for high impact, I sometimes go for a few well-positioned clumps of North American native Umbrella Leaf (Diphylleia cymosa). Used like a rodgersia would be, Umbrella Leaf adds bold texture among ferns and other delicacies. Furthermore, from discreet white flowers are borne cute clusters of blue to black fleshy fruits. Umbrella Leaf will surely leave your garden guests wondering.

USDA zones: 4 to 8
Water requirement: Moist soil
Light requirement: Full to partial shade
Mature size: 4 feet tall and 3 feet wide
Seasonal interest: Spring to fall
When to plant: Anytime CYAN Horticulture Mt. Omei Impatiens
(Impatiens omeiana)

Thankfully, not all choice woodlanders will inflict you with a multiple-year wait. Mt. Omei impatiens (Impatiens omeiana) is a hardy fellow of respectable vigor — within a couple of years it spreads into a sizable and dense colony, with plenty for division. It's just over a foot in height, and its foliage is velvety green marked with a central gold band. In late summer yellow flowers add to the show. Introduced over 30 years ago from China, this impatiens deserves broader recognition.

USDA zones: 6 to 9
Water requirement: Moist soil
Light requirement: Full to partial shade
Mature size: 1 1/2 feet tall and 2 1/2 feet wide; spreads
Seasonal interest: Spring to fall
When to plant: Anytime CYAN Horticulture Lady's Slipper Orchids
(Cypripedium spp and cvs)

No other plant has half the sex appeal of orchids. At the heart of stories of lure and lust, orchids are in the general psyche precious and desirable. Recent technological advances in tissue culture have somewhat democratized the growing of hardy terrestrial orchids. Purchased from certified propagators and carefully sited in a bright woodland, most of the Lady's slippers (Cypripedium spp and cvs) are indeed treasure-like. Hybrids seem easier to grow yet are never cheap to buy. Here is C. guttatum, photographed in the wilds of Mongolia.

USDA zones: 2 to 8
Water requirement: Well-drained to moist soil
Light requirement: Partial to dappled shade
Mature size: 1 1/2 tall and wide maximum
Seasonal interest: Early summer
When to plant: Anytime CYAN Horticulture Paris Polyphylla
(No common name)

With such a name as Paris (Paris polyphylla), this collector's woodland is a timeless addition to the garden. Its unmatched feminine silhouette, svelte and elegant, charismatic yet far from loud, embellishes simplistic compositions in moss, ferns and fine sedges. Difficult to source, attractive to slugs and in no hurry to bulk up, Paris is no foolproof choice. Yet it is so very pretty that I keep recommending it. Who's in?

USDA zones: 7 to 9
Water requirement: Moist soil
Light requirement: Partial to dappled shade
Mature size: 2 1/2 feet tall and 1 1/2 wide
Seasonal interest: Spring to summer
When to plant: Anytime