The plant is too young for us to make an ID with any certainty, especially since unrelated species sometimes have nearly identical foliage or change foliage shape/size as they mature. (Plant ID relies heavily on flower traits.) We can say that the plant does look similar to Aruncus, but if you don't happen to have a mature Aruncus that went to seed somewhere else in the yard, one appearing on its own is less likely since it's not commonplace in the wild in Maryland. (There are some documented populations in Baltimore County, but more isolated than in our western counties.) Still, perhaps a passing bird deposited a gift in its droppings, so you never know. You can leave it to mature and flower if you'd like (being a young plant and presumably perennial, this might not happen this year, but may be in its second or third year) and we're happy to attempt another ID when it blooms.

Miri

Aruncus are reportedly difficult to transplant after establishment, so it should be moved while still young, though we haven't seen a specific time of year mentioned in references we checked. You can either move it now, in early summer, or could wait until early autumn; either time should be followed by careful monitoring for watering needs as it acclimates and roots-in.

Miri

We think that looks like a tree seedling of our native Black Walnut.

Christine