Is this the sort of thing you are trying to do?
plants <- structure(list(Family = c("Nyctaginaceae", "Malvaceae", "Fabaceae",
"Euphorbiaceae", "Euphorbiaceae", "Euphorbiaceae"),
Genus = c("Abronia", "Abutilon", "Acaciella", "Acalypha", "Acalypha", "Acalypha"),
Species = c("fragrans", "theophrasti", "angustissima", "deamii", "monococca", "ostryifolia"),
Native = c("native", "non-native", "native", "native", "native", "native"),
C = c(6, 0, 7, 5, 4, 0),
Physiognomy = c("forb", "forb", "forb", "forb", "forb", "forb"),
Duration = c("perennial", "annual", "perennial", "annual", "annual", "annual"),
Common_Name = c("sweet sand-verbena", "common velvetleaf", "prairie acacia", "deams copperleaf", "slender copperleaf", "rough-pod copperleaf")),
row.names = c(NA,-6L), class = c("tbl_df", "tbl", "data.frame"))
Tbl <- table(plants$Genus) #counts how many occurences of each Genus
plot(Tbl)

barplot(Tbl)

Created on 2020-12-11 by the reprex package (v0.3.0)