This feels like a shot in the dark, but…
[name_f][/name_f][name_m]Julian[/name_m]
[name_f][/name_f][name_m]Julius[/name_m]
[name_f][/name_f][name_m]Leon[/name_m] (‘lion’ is a nature-adjacent meaning, right?)
[name_f][/name_f][name_m]Roman[/name_m]
[name_f][/name_f][name_m]Eli[/name_m]
[name_f][/name_f][name_m]Lyndon[/name_m] / [name_m]Linden[/name_m] (nature name, but traditional enough that your husband might not mind it [name_f][/name_f]- there’s [name_m]Lyndon[/name_m] B. [name_m]Johnson[/name_m], for one)
[name_f][/name_f][name_m]Lorenzo[/name_m]
[name_f][/name_f][name_m]Armand[/name_m]
[name_f][/name_f][name_m]Rafael[/name_m]
[name_f][/name_f][name_m]Elias[/name_m]
[name_f][/name_f][name_m]Zachariah[/name_m]
[name_f][/name_f][name_m]Timothy[/name_m]
[name_f][/name_f][name_m]Peter[/name_m]
[name_f][/name_f][name_m]Harvey[/name_m]
[name_f][/name_f][name_m]Adrian[/name_m]
[name_f][/name_f][name_m]Frank[/name_m]
[name_f]Sylvia[/name_f] (nature name that isn’t a word 
)
[name_f][/name_f][name_f]Sylvie[/name_f]
[name_f][/name_f][name_f]Elise[/name_f]
[name_f][/name_f][name_f]Leonie[/name_f] (again, means ‘lion’)
[name_f][/name_f][name_f]Rosalie[/name_f] (flower names count as nature names, but [name_f]Rosalie[/name_f] isn’t an [name_f]English[/name_f] word, either)
[name_f][/name_f][name_f]Rosalind[/name_f] (originally meant ‘gentle horse’, but has since picked up another meaning in another language [name_f][/name_f]- ‘beautiful rose’)
[name_f][/name_f][name_f]Lily[/name_f]
[name_f][/name_f][name_f]Rosemary[/name_f] (a herb, but used as a name often enough that it comes off as different from other word names)
[name_f][/name_f][name_f]Lucy[/name_f]
[name_f][/name_f][name_f]Marianne[/name_f] / [name_f]Marian[/name_f]
[name_f][/name_f][name_f]Madeleine[/name_f]
[name_f][/name_f][name_f]Eva[/name_f]
[name_f][/name_f][name_f]Vera[/name_f]
[name_f][/name_f][name_f]Gabrielle[/name_f]
[name_f][/name_f][name_f]Adelaide[/name_f]