We have very little information on cultivation of nut trees in home gardens, since they are so uncommonly grown locally and difficult to cultivate on a small scale due to space required and timetables needed to achieve regular harvests.

Rutgers University has some information (visit Nut Trees for New Jersey), and being in New Jersey, they are not too far removed from typical Maryland weather and soil conditions that their recommendations should largely apply here as well. Additionally, while we don't recommend or endorse one business over another, you could also consult with Edible Landscaping in Virginia, one source for a wide array of edible crop plants that should have experience in which cultivars are recommended for the mid-Atlantic.

For Pecan (Carya illinoinensis)

A noteworthy trait of these trees is their monoecious flowers, which means that male and female flowers open separately but on the same tree. Some cultivars open the male flowers first, then the female afterwards (to avoid self-pollination) while other cultivars do the opposite. A few cultivars may be somewhat self-pollinating and may crop solo, but they are in the minority. To ensure a good harvest, it's recommended that one protandrous (also called Type I, with male pollen shedding first) and one protogynous (also called Type II, with female flowers being receptive first and pollen shedding later) variety are paired as a set for pollination. Therefore, given how large Pecan trees mature, this will take up a lot of space in the typical home garden. Plus, trees will need to mature for many years before beginning to produce a crop.

For Walnut (Juglans)
English/Persian Walnut (Juglans regia) tends to be the crop that wholesale tree growers would stock, but native Black Walnut (Juglans nigra) might be another option.

Let us know if you have further questions. 

Emily