You have so many great suggestions already! Maybe at least a couple of these will be new 
[name_f][/name_f][name_f]Brynn[/name_f] [name_f]Aspen[/name_f], [name_m]Levi[/name_m] [name_m]Cedar[/name_m], and…
[name_f]Arden[/name_f], [name_f]Afton[/name_f], [name_f]Delaney[/name_f], [name_f]Waverly[/name_f], [name_f]Verity[/name_f], [name_f]Vesper[/name_f], [name_f]Wellesley[/name_f], [name_f]Sage[/name_f], [name_m]Lane[/name_m], [name_m]Adair[/name_m], [name_f]Shea[/name_f], [name_f]Willow[/name_f], [name_f]Haven[/name_f], [name_f]Selah[/name_f]
[name_f][/name_f][name_m]Boaz[/name_m], [name_m]Jonah[/name_m], [name_m]Asher[/name_m], [name_m]Hayes[/name_m], [name_m]Asa[/name_m], [name_m]Abel[/name_m], [name_m]Luke[/name_m], [name_m]Brooks[/name_m]
[name_f][/name_f]For nature-themed middles, I like [name_f]Sage[/name_f] and [name_f]Willow[/name_f], also [name_f]Maple[/name_f], [name_m]Oak[/name_m], [name_m]Spruce[/name_m], [name_m]Noble[/name_m] (like the fir), [name_f]Sequoia[/name_f], [name_f]Madrona[/name_f], [name_m]Linden[/name_m], [name_f]Plum[/name_f], [name_m]Yarrow[/name_m], [name_m]Reed[/name_m], [name_f]Briar[/name_f], [name_f]Hazel[/name_f], [name_m]Hawthorne[/name_m], [name_m]Ash[/name_m]