Hardy is a relative word. For some it means frost tolerant, for me it necessarily means able to withstand -25 F. This renders most lists of “hardy” nitrogen fixers obsolete, save a few over-used specimen.
In order to keep the northern food forests from becoming a monoculture of Siberian peashrubs then, here is my own list of nitrogen fixers hardy to zone 5 or lower. More will be added. If any nitrogen fixer aficionados notice a questionable species, don’t hesitate to let me know in the comments. I recently added comments on those I have but haven’t written posts on. Highlighted names are linked to posts about the plant
- Albizia julibrissin
- Alnus cordata
- Alnus incana
- Alnus serrulata
- Alnus glutinosa
- Alnus ruber
- Alnus viridis
- Amorpha nana (planted seed, got one plant)
- Amorpha fruticosa
- Amorpha canescens
- Amorpha glabra
- Apios americana
- Astragalus glycyphyllos
- Astragalus neglectus
- Astragalus canadensis (started from seed this year and already having more luck than with glycyphyllos)
- Astragalus crassicarpus (bought plant but it died)
- Astragalus striatus
- Baptisia alba (several young plants from seed)
- Baptisia australis
- Baptisia bracteata
- Baptisia tinctoria
- Caragana arborescens (several)
- caragana korshinskii (seeds in strat.)
- Caragana microphylla
- Caragana aurantiaca
- Caragana boisii
- Caragana frutex
- Caragana decorticans
- Caragana pygmeae
- Caragana brevispina
- Ceanothus americanus
- Colutea arborescens
- Comptonia peregrina
- Cytisus scoparius (several)
- Dalea purpurea
- Dalea candida
- Dalea villosum
- Desmodium canescens
- Desmodium canadense (getting one this year as plant. update: died)
- Desmodium ciliare
- Desmodium cuspidatum
- Desmodium perplexum
- Desmodium paniculata
- Dryas octopetala
- Eleagnus umbellata
- Eleagnus multiflora
- Eleagnus angustifolia
- Eleagnus orientalis (got berries this year that are much larger -though not as flavorful as the native “olives”)
- Eleagnus comutata
- Galega hartlandii (I have “Lady Wilson”)
- Galega officionalis
- Genista tinctoria (one young plant growing well)
- Glycyrrhiza lepidota
- Gymnocladus dioica
- Hedysarum alpinum
- Hedysarum boreale
- Hippophae rhamnoides (killed several but keep buying larger plants in hopes of them living. I think they disagree with my clay soil, prefering sand)
- Laburnum anagryoides (my neighbor has a gorgeous, large specimen I have so far failed to get a healthy cutting from. Seeds have sprouted, but not endured)
- Laburnum alpinum
- Lathyrus tuberosus (a happy patch)
- Lathyrus latifolia (large patch right up the road from me. See Daylilies)
- Lathyrus venosus
- Lathyrus ochroleucus
- Lathyrus maritimus
- Lespedeza bicolor
- Lespedeza capitata
- Lespedeza thunbergii
- Lupinus perennis (lots, and they are beautiful blue!)
- Lotus corniculata (grows around here but I’m still trying to coax into the food forest)
- Maakia amurensis (two young plants)
- Pediomelum subacaule (got bulbs, got bloom, but has been limping along)
- Pueraria lobata (‘Sherman’s Ghost’ which is variegated and less aggressive. Update: died over winter)
- Psoralea tenuiflora
- Robinia pseudoacacia
- Robinia hispida (came up easily from seed. Very frost sensitive seedlings. Two got to food forest)
- Robinia viscosa
- Securigia varia (I’m ecstatic to see the crown vetch by the road is creeping into the food forest. Taxing it of nitrogen rich growth accordingly)
- Senna marilandica
- Senna hebecarpa (N-fix 6: Senna hebecarpa)
- Sheperdia argentea (two plants from Oikos had nice nodules when planted)
- Sophora japonica
- Sophora alopecuroides
- Sophora davidii (one plant, seems happy)
- Tephrosia virginiana
- Trifolium pratense
- Vicia gigantea
- Vicia sylvatica
- Vicia villosa
- Wisteria americanum
- Wisteria japonica
- Wisteria chinensis
- Wisteria fruticosa (got a rooted cutting in an online trade that has lived happily. Update: died after two years despite looking very happy.)
Mortal Tree 