Empress Wu Hosta

Overview

'Empress Wu' is widely regarded as the largest hosta cultivar ever introduced, forming a colossal mound of deeply textured blue-green foliage that can top 4 feet tall and spread wider still (Hosta 'Empress Wu'). Where most hostas are a tidy edging plant, this one reads as a shrub-scale specimen. It is grown almost entirely for its dramatic leaf size and presence rather than its modest flowers.

Origin & Background

Garden hostas descend from species native to northeast Asia - Japan, Korea, China and the Russian Far East - where they grow on wooded slopes and stream banks. 'Empress Wu' is a complex hybrid selected in the United States, discovered by Brian and Virginia Skaggs and introduced to the trade around 2009 under plant patent. It was named for Wu Zetian, the only woman to rule China as emperor, a nod to its commanding scale.

Appearance

The foliage is the whole point: broad, heart-shaped leaves in a deep, dusty blue-green, heavily corrugated and thick-substanced, individual blades often reaching 18 inches long and nearly as wide on a mature clump. The plant builds slowly into an upright, vase-to-mounded form roughly 4 to 5 feet tall and 5 to 6 feet across when fully established, which takes several seasons. In early-to-mid summer it sends up scapes of pale lavender, near-white bell flowers held just above the leaves. The blue cast is a waxy bloom that is strongest in cooler weather and part shade; foliage yellows and dies back after autumn frost, with the plant fully dormant in winter.

Why People Grow It - Qualities & Benefits

• Unmatched scale - a single specimen fills a large shaded corner the way a shrub would
• Bold blue-green, corrugated leaves that add heavy texture and cool color to shade
• Thick leaf substance gives it better slug resistance than thin-leaved hostas
• Reliable, low-fuss perennial that returns bigger each year in the right spot

Care

Light: Part shade to full shade; morning sun with afternoon shade is ideal, and deep shade is tolerated though growth is slower. Water: Consistent, even moisture - this large plant is thirsty, especially while establishing and during dry spells. Soil: Rich, deep, well-drained soil high in organic matter; slightly acidic to neutral pH around 6.0 to 7.0. Hardiness: USDA zones 3 to 9. Bloom or Season: Foliage plant from spring emergence through autumn, with pale lavender flowers in early-to-mid summer; leaves yellow and collapse after frost, no true autumn color. Extra: Give it room and patience - it needs three to five years to reach full imperial size, so do not crowd it. Toxic to cats and dogs. Hostas contain saponins; ingestion causes vomiting, diarrhoea and depression.

Planting & Propagation

Plant in spring or early autumn in a hole amended generously with compost, setting the crown at soil level and spacing at least 5 to 6 feet from neighbors to allow for the eventual spread. Mulch to conserve moisture and keep the root zone cool. Propagate by division in early spring as the shoots (eyes) emerge: lift the clump, cut through the crown with a clean sharp spade so each division carries several eyes and roots, and replant immediately - though many growers leave this slow-maturing cultivar undivided to reach maximum size.

Common Problems & Pests

• Slugs and snails, especially on young or shaded plants, though thick leaves resist them better than most
• Deer and rabbits, which browse hostas readily and can strip a plant overnight
• Crown rot and foliar diseases in soggy, poorly drained soil, plus leaf scorch if exposed to hot afternoon sun

Toxicity & Safety

'Empress Wu', like all hostas, is toxic to cats and dogs. The leaves and other parts contain saponins; when chewed or eaten they irritate the digestive tract, causing vomiting, diarrhoea and depression (lethargy). Keep pets from grazing on the foliage, and contact a veterinarian if a significant amount is ingested or symptoms are severe.

Pros & Cons

Pros

• Spectacular, largest-in-class specimen presence for shade
• Tough, cold-hardy and long-lived once established

Cons

• Slow to reach full size and needs a lot of space
• Toxic to cats and dogs, and attractive to deer

Best Suited For

• Shaded or woodland gardens needing a bold focal-point plant
• Patient gardeners with room for a large, statement perennial

FAQ

How big does Empress Wu really get?

In good conditions it reaches about 4 to 5 feet tall and 5 to 6 feet wide, making it the largest common hosta cultivar - but expect three to five years of steady growth before it hits that mature scale.

Does it need shade, or can it take sun?

It performs best in part to full shade. It can handle morning sun, but hot afternoon sun scorches the leaves and fades the blue coloring, so a sheltered, shaded spot with rich moist soil is ideal.