I see foragers returning to the hive with their corbicula (pollen basket) full of pollen. Especially at the end of winter I am curious what is in bloom that could be providing pollen. Perhaps these tables will help.

Major Nectar (N) and Pollen (P) Plant Sources of Oklahoma

Plant Name	Dates of Bloom
Alfalfa (N)	May 10 to Frost
Cotton (N&P)	July 10 to Frost
Hairy vetch (N&P)	April 20 to July 31
Persimmon (N&P)	May 15 to June 15
Plains sage (N&P)	June 1 to October
Smartweed (N&P)	July 1 to October
Spanishneedle (N&P)	Aug. 1 to Frost
Vitex (N&P)	May 15 to Frost
White sweetclover (N&P)	May 5 to July 25
Yellow sweetclover (N&P)	April 20 to July 10

Even though it is from another region, this pollen color chart might also be helpful in identifying the pollen by color.

Minor Nectar and Pollen Plant Sources of Oklahoma

Plant Name	Dates of Bloom
Bee bee tree (N&P)	July 1 to August 31
Bindweed (N)	May 15 to Sept. 30
Black locust (N&P)	April 10 to May 20
Broomweed (N&P)	July 5 to Nov. 10
Dandelion (N&P)	April 1 to June 1
Elm (P)	Feb. 25 to March 25
Lawn clover (N&P)	March 20 to July 1
Lemon monarda (N&P)	June 1 to October
Maple (N&P)	Feb. 20 to May 5
Milkweed (N)	May 10 to Sept. 5
Pear (N&P)	March 15 to April 8
Redbud (N&P)	March 10 to April 15
Sand plum (N&P)	March 20 to May 10
Sumac (N&P)	May 10 to August 1
Sunflower (N&P)	July 1 to Frost
Tame plum (N&P)	March 20 to May 5
Willow (N&P)	March 20 to April 10

For more information see the Oklahoma State Extension fact sheet at https://extension.okstate.edu/fact-sheets/nectar-and-pollen-plants-of-oklahoma.html