R. fictolacteum and / or R. rex
by Howard Slonecker
Fig 25. Young shoots of R. rex showing the typical
grey-white tomentose covering.
In many of the rhododendron gardens of the Pacific Northwest there is a species of the "big leaf" type that has been called R. fictolacteum by some and R. rex by others.
These plants, or at least most of these plants, came originally from the old Barto place in the hills west of Junction City, Oregon, where, I understand, Mr. Barto grew them from seed. It is my contention that the proper species name for these plants is R. rex.
It is not known to me whether any records of these plants survived the fire which destroyed most of Mr. Barto's records or whether he, in any way, passed the name of these plants on to anyone else. However, it remains that these plants are posing under two names one of which must necessarily be an alias.
In running through the descriptions of R. fictolacteum and R. rex in The Species of Rhododendron published by the Rhododendron Society of Great Britain I found that there are several distinguishing characteristics. R. fictolacteum is described as having 12 to 15 flowers to the truss, R. rex as having 20 to 30; R. fictolacteum is described as having an oblique-campanulate shaped corolla 3 to 4 cm. long and 6½ cm. across, R. rex as having a tubular-campanulate corolla 5 cm. long; R. fictolacteum is described as having pedicels 3 cm. long and those of R. rex 1½ to 2 cm. long. I can find nothing in the descriptions of the leaves that is particularly distinguishing except that the color of the indumentum of R. fictolacteum is buff to rusty brown and that of R. rex grey to pale buff. To me the outstanding distinguishing characteristic is the color of the young growth shoots. R. fictolacteum is described as having cinnamon colored young shoots and those of R. rex grey-white.
The plant in my garden has decidedly whitish new growths with no trace of brown or tan coloring. The accompanying picture shows this fairly well (Fig. 25). It has a tight truss of about 22 flowers and the corolla is as long as it is wide. I have never seen R. fictolacteum bloom but from the description I would assume that it has somewhat more shallow flowers than R. rex. I would also assume from the number of flowers and the length of the pedicels that the former has a more open truss.