The only candidate that meets almost all of those criteria is American Hazelnut. They are not self-pollinating and more than one cultivar (or seed-grown wild-type plant) would be needed to pollinate each other in order to get a harvest. Other nut-bearing trees native to Maryland, which aren't many, will mature well over 40 feet high, even though it will take them a few decades to do so. Few are self-pollinating.

Rutgers University has a web page about selecting and growing hazelnuts, though primarily in reference to using American-European hybrids. Filbert Blight can be a fatal fungal disease of hazelnuts, and the inherent resistance of the native species to this infection is important, but incorporating the better nut quality and yields of the European species is what prompted hybridization programs. Hazelnuts are large shrubs, so take up much less root room and branch space than other nut-bearing trees. Mildly alkaline/basic soil conditions should not be a problem; nor should clay, as long as it drains well.

The other locally-native nuts are Black Walnut (Juglans nigra) and various Hickories (Carya species). Pecan (Carya illinoinensis) is in the same genus as Hickory, but does not grow wild in Maryland and is barely winter-hardy here because its native range is mostly south of us. (It has been observed growing in several MD counties, but having escaped cultivation, not naturally.) Butternut (Juglans cinerea) is a species related to Black Walnut that also grows in Maryland, but it is state-rare and generally not available in horticulture. All of the above nut trees mature in the range of 60 to 100 feet, albeit somewhat slowly. There are two fungal diseases that can be fatal (if contracted) to both Black Walnut and Butternut; neither is widespread in Maryland at present, though.

American Chestnut (Castanea dentata) hybrids are still being tested for Chestnut Blight resistance, a fatal fungal disease. Chestnut growers tend to cultivate Chinese Chestnut (Castanea mollissima) instead, though there are a couple hybrid varieties. If you are interested in trying to grow American Chestnuts, you could inquire with organizations like the Maryland Chapter of the American Chestnut Foundation for their feedback or suggestions for hybrids or cultivars that hold a greater likelihood of success (both for tree longevity and nut yield, if the latter is important to you beyond the tree's intrinsic wildlife value). A mature height of a successfully-grown American Chestnut would be around twice your desired size.

Allegheny Chinkapin (Castanea pumila), a species related to American Chestnut and which is also native locally, matures smaller and produces edible nuts, though fewer in number than Chestnut. Its mature height is often under 40 feet, but references to soil pH suggest it prefers slightly acidic conditions; some sources say it can take a pH up to 8.0, so we are not certain how particular they may be. Chinkapin is wind-pollinated, like all of the above nut trees, but is not self-pollinating, so at least two plants would be needed to get a harvest.

Unlike "conventional" fruit trees (apple, peach, cherry, etc.), nut trees of the age typically sold at nurseries or mail-order sources need more time to mature before beginning to bear. It would not be uncommon for the plant to need about ten years after planting to start bearing decently well. Shrub-stature plants, like the American Hazelnut and probably the Allegheny Chinkapin as well, tend to need less time to mature before bearing a crop.

Miri

Hello Steven,

For wind pollination distance, it's likely several hundred feet or more that would be sufficient for pollination, but the closer plants are to their pollen partner, the better overall for guaranteeing a decent crop. A few houses away is likely fine if the building layout doesn't happen to interrupt the main wind channels through the neighborhood. That said, for commercial operations, hazelnut rows are often planted fairly close (we've seen recommendations for 20-foot spacing or so), and one reference says a maximum windblown distance should be 80 to 100 feet. Therefore, if you can fit them both in one yard, that would be the safest bet. Rutgers also addresses some of the complicating factors when choosing a pollinator, since as with many nut trees, the pollen-bearing and pollen-receptive flowers or parts of the flowers are not always open at the same time, or in the same order. (Some varieties may produce pollen first, then become receptive to pollination, while others may do the opposite. In that case, pairing one tree from each group is best, since that gets you pollen flowing from one tree to the other first, then the reverse, so each is well-pollinated.) We don't have more specific advice outside of what other Extension resources suggest since hazelnuts and other nut trees are not commonly cultivated in Maryland farms and home gardens.

Red Maples are sturdier than Silver Maple, yes, though both trees can mature fairly large and grow quickly. We would not recommend using pruning to significantly reduce the height of any tree that is too tall for where it is growing, including chestnuts. Even if the wood is fairly strong, that does not mean the tree would not become vulnerable to wood decay invasion at any of the pruning points, which would seriously endanger its long-term health (and later, its stability). Tree topping is not a practice condoned by certified arborists, and while there are other ways of pruning larger trees to reduce canopy size that are less damaging to a tree, it's always best to choose a tree whose mature height is within the size that can be accommodated by where it will be growing. Additionally, the more pruning that would need to be done on a mature nut tree, the less of a harvest it will be capable of producing.

Miri