- apheliotropic
- apheliotropism
- aphyllous
- apocarpous
- apocynaceous
- apogamic
- apogamy
- apothecia
- apothecium
- apple-tree
- araceous
- arachnoid
- araliaceous
- araucaria
- archangel
- archesporium
- archil
- aristate
- archespore
- areca
- aristae
- artichoke
- asafoetida
- asci
- ascomycetes
- asp
- asparagus
- aster
- astragalus
- argyranthous
- aril
- arista
- aroid
- arnica
- arum
- asclepiadaceous
- ascus
- ascospore
- ash
- aspen
- aspergillus
- asphodel
- assafoetida
- assurgent
- arbutus
- argyrophyllous
- arrowroot
- aubergine
- auricula
- auriculae
- auxanometer
- awl-shaped
- axilla
- azalea
- awn
- axillae
- bacciferous
- axil
- axillary
- azolla
- baby-sitter
- autumnal
- avocado
- bald cypress
- balloon vine
- balsam
- balsaminaceous
- banana
- banian-tree
- basidium
- bay-tree
- baobab
- beech
- beet
- bell-flower
- belladonna
- barberry
- barbery
- barrenwort
- basidia
- basidiomycetes
- basil
- bass
- bass-wood
- bast
- bastard slip
- bay
- beard
- begonia
- bell
- bent
- berberis
- bere
- berried
- berry
- berth
- betel
- betony
- bilberry
- big tree