110 HANDBOOK 14 8, U.S. DEPARTMENT OF AGRICULTURE 



7. Thorns stout, to 1 inch long; twigs shiny, reddish brown, 

 hairless or nearly so; "berries" purplish black, hairless; com- 

 monest hawthorn in e. Oreg., e. Wash. 



Douglas hawthorn (Crataegus douglasii). 

 7. Thorns slender, to 2 l / 2 inches long; twigs brown. 

 8. "Berries" dark red to purplish, hairless; thorns averaging 

 shorter, straight; shrubs or small trees, to 15 feet high. 



Columbia hawthorn (Crataegus columbiana) . 

 8. "Berries" coral red, hairy; thorns longer, often reflexed; 

 shrubs to 10 feet high. 



Piper hawthorn (Crataegus piperi). 2i 

 6. Plants without thorns. 

 9. Spines present. 



10. Twigs densely white-woolly-hairy; spines recurved or 

 spreading, formed from hardened, persistent midribs of 

 primary leaves; buds and leaf scars indistinct, in spine 

 axils; flower-head bracts 5-6 in a single series, persistent; 

 stiff, much-branched shrubs to 5 feet high; dry, sandy or 

 alkaline sites, se. Oreg., not reported from Wash. 



cottonthorn horsebrush (Tetradymia spinosa). 

 10. Twigs not densely white-woolly-hairy, often with scattered 

 prickles and/or bristles in addition to simple or 3- to 9- 

 parted spines bordering the usually narrow leaf scars; 

 bundle traces 3; buds evident, somewhat egg- or spindle- 

 shaped; bud scales papery, several, overlapping, persistent 

 after buds open; short, spurlike twigs common; pith 

 spongy; erect or spreading shrubs, often with arching 

 branches and crown-sprouting or layering after fire or top 

 injury; alternate hosts of white pine blister rust.^ 



currants, gooseberries (Ribes spp.). 

 11. Spines 3- to 9-parted, usually to about % inch long; 

 prickles and/or bristles commonly present, especially in 

 sunny sites; twigs brown or deeply straw-colored; buds 

 symmetrical, at 30° angle to twig; fruit-cluster stalks 

 (peduncles) elongate, often drying-persistent with 4-20 

 bracted berry stalks (pedicels) attached; berries with 

 gland-tipped bristles, usually not persistent- _ currants. 

 12. Twigs with gland-tipped bristles; spines rigid, rather 

 stout; buds rounded at tips, end buds about same size 

 as side buds; stiff-branched shrubs to 4 feet high; on 

 rocky exposed sites at higher (often subalpine) 

 altitudes .gooseberry currant (Ribes montigenum). 

 12. Twigs finely whitish-hairy but bristles not gland- 

 tipped; spines less rigid, rather slender; buds pointed 

 at tips, end buds larger than side buds; much-branched 

 shrubs, erect and to 3 or 4 feet high, or, if in shade, 

 trailing and with weaker spines and prickles; moist 

 sites in open mountain woods; very susceptible to 

 white pine blister rust. 



prickly (or swamp) currant (Ribes lacustre). 



24 Piper hawthorn is listed in the Check List of Native and Naturalized Trees 

 of the United States (U. S. Dept. Agr., Agr. Handb. 41. 1953) as a synonym of 

 Columbia hawthorn; these need field study. 



