The differences between different species of Synanthedon are very minute. Overall similarities are great, and for this reason it can be difficult to classify individual specimens.
According to Duckworth and Eichlin, this is the "most polymorphic species of Sesiidae." Most specimens are blue-black with various patterns of orange and red on the wings, legs, and abdomen. The degree of opacity on the wings is highly variable, and wingspan is 7-12 mm. Females and males appear very similar.
The known range of Synanthedon polygoni is from Chihuahua and northern Baja California north to Alaska.
Synanthedon polygoni uses several hosts, many of which are different types of buckwheat (Eriogonum). It is known to use the northern buckwheat (E. compositum), California buckwheat (E. fasciculatum), wild buckwheat (E. gracile), desert trumpet (E. inflatum), seaside wild buckwheat (E. latifolium), coast buckwheat (E. parvifolium), and the woolly buckwheat (E. wrightii). Other possible hosts are the granite gilia (Leptodactylon pungens) and beach knotwood (Polygonum paronychia), as well as most species classified Polygonaceae.