Native pollinators in managed forest landscapes
(Answers from Rachel Zitomer)
Q). Do you have a list of pollinator plants suitable for Eastern Oregon and Washington?
A). Unfortunately I don’t have any guides on hand specific to the eastern part of these states, but some good general guides for different regions can be found on the Xerces society website: https://xerces.org/pollinator-conservation/pollinator-friendly-plant-lists
A few I can think of off the top of my head are
Shrubs and trees:
- Rabbitbrush
- Willow
- Oregon grape
- Snowberry (multiple species)
- Spirea (multiple species)
- Ceanothus (many species)
- Gooseberry/currant (many species)
- Elderberry
- Choke cherry
- Red osier dogwood
- Manzanita/kinnikinnick
- Huckleberries (many species)
- Mock orange
- Ninebark
- Oceanspray
- Wild roses
Other native plants:
- Native lupines (many species)
- Native cinquefoils (there are several west of the cascades)
- Native fleabanes (there are several west of the cascades)
- Western mountain aster
- Mountain monardella
- Checkerblooms (there are few species in Oregon
Q). What are some good ways to promote native pollinators (e.g. providing nesting materials for mason bees and other narrow cavity nesters)
A). General advice is to minimize use of insecticides and plant flowering species of different types (different families, shapes, colors, a mix of shrubs, trees, perennials, herbaceous wildflowers) which flower at different times in the year. Some guides for native plants that flower at different times of year can be found here.
Some good ways to provide nest sites (in forested areas it’s best to do these things in areas with significant light in the understory, like oak woodlands, thinned stands, canopy gaps, young [pre-canopy closure] stands, and forest edges):
- Keeping around some standing snags, stumps, and softening logs on the ground
- Installing mason bee houses and rearing their cocoons (here’s a good guide from OSU extension: https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/em9130.pdf)
- Retain some patches of bare dirt for ground nesters. Abandoned ground-rodent homes are also often colonized by ground-nesting bumble bees.
- Consider planting or keeping around native plants with pithy stems such as whitebark blackberry, thimbleberry, or salmonberry, spirea, gooseberry, ninebark, nootka rose, oceanspray and elderberry. Leave dead stems/canes on the plant whenever possible since that’s where stem-nesters will colonize.
Q). Was the bee population highest in post fire areas where salvage logging occured?
A). Yes!
Q). Common name for some of the native Phacelia plants?
A). Actually the common name for most Phacelia species is Phacelia! For example in western Oregon I see a lot of varileaf phacelia and some lacy phacelia. Some people also call it scorpionweed.
Q). Would’nt soil compaction from heavy equipment use would be detrimental to ground nesting?
A). Soil compaction or big disturbance may damage existing nests (but many of them are deeper than you might think and can withstand quite a bit of disturbance on the ground surface, even fire!) but it seems that compacted soil is an especially attractive nesting substrate for a lot of soil-nesters.
Q). Please talk more about pruning roses – how long of a stub should you leave? Would they use the cut stems on the ground?
A). A mix of stem lengths (8 to 24+ inches) and diameters (1/8”-1/3”) is ideal because different species have different preferences. I’m not sure whether they’ll use cut stems on the ground, but I think the general advice from bee-friendly gardening folks is to leave dead flower stalks standing over the winter, cut back the flower heads early in the spring, leaving standing stems with an open (cut) end and then in the summer the new flowers may well grow around those stems so they’re not too unsightly. Female stem nesters provision nests spring-summer and the larvae overwinter in the stems until the following spring/summer.