Marin Master Gardeners
University of California
Marin Master Gardeners

Plant Guide

Iris douglasiana

Common Name
Pacific Coast Iris
CA Native
California Native
Plant Type
Perennial
Size
18" - 36" x 15" - 24"
Flower Color
Blue, purple, White, Maroon, Yellow
Bloom Time
  • Spring
Leaves
Green, Strap-Leaves
Evergreen
Evergreen
Deer Resistant
Wildlife Value
  • Bees
Growth Rate
Fast
Hardiness
Hardy
Adverse Growth Factors
None
Special Features
  • Good Under Oaks
  • Low Maintenance
  • Showy Flowers
Water Use
  • Drought Tolerant
  • Low
Soil pH
5.5-6.4 (acid)
Exposure
  • Partial Shade
  • Shade
Soil Type
Not Particular
Drainage
Good Drainage
Description and Cultural Plant Tips

There are 11 species of native Pacific Coast Irises (PCI), one of which is I. douglasiana. I. douglasiana has been been successfully hybridized with other PCI in Ca., Washington and Oregon to produce stunning flowers of varying colors that can grow up to 1.5 feet tall. The collection of hybrids are often called Pacific Coast Hybids in the nurseries.

In nature, they are found  in meadows and woodlands near the coast and do best in a mild, maritime climate. In gardens near the coast they will tolerate full sun, however, inland it is best to plant them in light shade during the hottest part of the day. While PCI's can grow in a whide range of soils, they prefer a slightly acidic (pH 5.5 - 6.5) soil to which considerable peat or humus has been added. Feeding should be done in the spring using a balanced slow release camellia/azalea fertilizer. Water once or twice a month in the summer once PCI is established. Mulching is recommended to conserve water in the root zone. They do tend to look a little ratty if no water is applied in the summer.

PCI's resent being divided so it is best to let them grow undisturbed for a few years. When the clumps get large enough (2 -3 years) they can be transplanted successfully when their roots are actively growing in the late fall (after rain) or early spring. Check the roots to see if they are white and plump before you transplant. It is vital to keep roots moist when you are lifting and dividing them. Water immediately after transplanting  keeping moist until established.

PCI's have few pests or diseases. However, if planted in areas with poor drainage, PCI's can develop rhizome rot and fungal or viral diseases. They can also be attached by aphids, slugs and snails.

Master Gardener Comments

These irises do very well under oak trees inland since they do not require much water in the summer. I plant them with other natives such as Shooting Stars and Hounds Tongue for a pretty spring display.

Varietals

I. douglasiana 'Amiuuita' - blue bi-tone with a purple single spot

I. douglasiana ' Canyon Snow' - white

I. douglasiana 'Harland Hand' - purple, long-blooming season

I. douglasiana 'Mendocino Banner' - white with purple veins

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