Cyrtomium–commonly called holly fern–is a smallish fern with stiff, dark green leaves that resemble holly leaves. Fronds are large, dark green, glossy, and leathery. It is evergreen in mild climates, deciduous in cold winter regions.
Crytomium thrives outdoors in mild-winter regions. It can be grown as a houseplant where it will grow well even in poor light. It grows easily under artificial light.
Outdoors grow Crytomium in woodland areas and shaded areas of borders or rock gardens. It is a handsome border for tree or shrub areas.
Get to Know Cyrtomium
- Plant type: Fern
- Growing zones and range: Zones 6 to 11
- Hardiness: Half-hardy; will not survive temperatures below 25°F (-4°C).
- Optimal growing temperature: day, 68° to 72°F (20° to 22°C); night, 60° to 65° (16° to 18°C).
- Height and width: 12 to 24 inches (30-60cm) tall and 24 to 36 inches (40-91cm) wide
- Foliage: Stiff, dark green fronds are glossy and leathery; fronds resemble holly leaves; deciduos in cold-winter regions.
- Flowers: Non-flowering
- Uses: Shade garden, houseplant
- Common name: Holly fern
- Botanical name: Cyrtomium
- Family name: Dryopteridaceae
- Origin: Eastern Asia, India, southern Africa and Hawaii
Where to Plant Cyrtomium
- Light outdoors: Plant in part shade to full shade.
- Light indoors: Does best in eastern exposure, but will adapt to poor light from northern exposure. Does well under artificial light.
- Soil outdoors: Grow in moist, humusy, well-drained soils.
- Soil indoors: Use a fern mix, with good drainage.
When to Plant Cyrtomium
- Set Crytomium outdoors in spring.
Planting and Spacing Cyrtomium
- Space Crytomium 24 to 36 inches (40-91cm) apart.
How to Water and Feed Cyrtomium
- Water: Let soil dry slightly between thorough waterings. Indoors mist Crytomium frequently; it prefers humidity of 60% to 70%.
- Feeding: Fertilize Cyrtomiyn every third or fourth watering during growing season, with mild liquid fertilizer.
- Crytomium may rest during fall and winter. Water lightly and withhold fertilizer.
Growing Cyrtomium as a Houseplant
- Cyrtomium does best in bright light, average to cool temperature, and medium humidity.
- Cyrtomium can tolerate low light, dry air, and drafts.
- The soil should be allowed to dry moderately between thorough waterings.
- Feed Cyrtomium occasionally throughout the year.
Cyrtomium Pests and Diseases
- Check Crytomium for aphids, fungus gnats, mealybugs scale, slugs, and snails.
- Propagate Crytomium by crown division or spores. If spores are to be collected for propagation, do not wash undersides of fronds when spores are maturing.
- Spores are easily carried by wind, and species plants have escaped gardens and naturalized in certain warm winter regions.
Cyrtomium Varieties to Grow
- Cyrtomium falcatum, holly fern. Erect, with fronds reaching 2 to 3 feet tall; individual pinnae (section of the fronds) are relatively large, leathery, and often more than an inch long and nearly as wide; fronds are glossy dark green and leathery to the touch; readily adapts to the indoors..
- C. fortune var. intermedia. Hardier than C. falcatum; use as a textured ground cover in a woodland garden.