Plant Data Sheet

Pacific Rhododendron Rhododendron macrophyllum

picture taken from http://www.cnr.vt.edu/dendro/dendrology/syllabus/rmacrophyllum.htm

Range

Southern British Columbia to Northern California.

Climate, elevation

Moist to dry climate found from the coast to middle elevations.

Local occurrence (where, how common)

Fairly common understory in mixed conifer forests. Less abundant in Washington, very common south of the Siuslaw River.

Habitat preferences

National Wetland Indicator species, however no anaerobic tolerance.

Plant strategy type/successional stage (stress-tolerator, competitor, weedy/colonizer, seral, late successional)

No information on succession other than “This species sprouts well after fire or cutting and brings an encouraging touch of colour to cleared areas.” (Pojar/Makinnon) This suggests a colonizer habit.

Associated species

Western Hemlock, Sitka Spruce, Redwood, Douglas Fir, Silver Fir

May be collected as: (seed, layered, divisions, etc.)

Propagated by seed, cuttings.

Collection restrictions or guidelines

Collect seed late summer to early fall.

Seed germination (needs dormancy breaking?)

The seeds require light for germination.

Seed life (can be stored, short shelf-life, long shelf-life)

Pacific rhododendron seeds germinate without stratification and are viable for up to 2 years.

Recommended seed storage conditions

A cool, dry, dark place is recommended.

Propagation recommendations (plant seeds, vegetative parts, cuttings, etc.)

Seedling vigor is medium 

Soil or medium requirements (inoculum necessary?)

Moist well drained soil, low nitrogen availability. Sandy loam would be best. Inoculation is not necessary, however many studies have shown a mycohirrizal interaction.

Installation form (form, potential for successful outcomes, cost)

Container plants grown from seed or cutting.

Recommended planting density

3-4m spacing

Care requirements after installed (water weekly, water once etc.)

Aeration is a key requirement due to its shallow root system, as is a moist acidic soil.

Normal rate of growth or spread; lifespan

Perennial. The flowers are pollinated by bees and plants begin to bear seed when they are 5 years old. Pacific rhododendron seeds germinate without stratification and are viable for up to 2 years. The seeds require light for germination. The will typically reach 3 m at 10 yrs. They reach up to 5m at maturity. If aboveground portions are killed, Pacific rhododendron can regenerate vegetatively by sprouting from stem bases and from the rootcrown.

Sources cited

http://www.cnr.vt.edu/dendro/dendrology/syllabus/rmacrophyllum.htm

http://www.fs.fed.us/database/feis/plants/shrub/rhomac/

http://plants.usda.gov/

Hitchcock, C. Leo; Cronquist, Arthur. Flora of the Pacific Northwest: An Illustrated Manual. University of Washington Press. 1987.

MacKinnon, Andy; Pojar, Jim. Plants of the Pacific Northwest Coast:Washington, Oregon, British Columbia and Alaska. Lone Pine Publishing. 1994.

Data compiled by

Christer Lundstrom 4/15/03