Plant
Oklahoma gardeners will want to take advantage of this month being an excellent month to plant bare rooted trees, shrubs, ground covers, vines, plants that are permanent. 
Begin vegetable garden with cool season plants like onions, radishes and potatoes (see article on the Best onions and potatoes for Oklahoma gardeners).
Finish up transplanting
Fertilizer
If you have [...]

Plant All remaining daffodils and tulips that were not planted earlier. Oklahoma Red Dirt Bulb Planting 101
Transplant all remaining shrubs that need to moved.
Trees, shrubs, and vines.

Fertilizer Organic fertilization of newly planted trees [...]