Cold ( zone 5 ) hardy N fixers

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.

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One of the few hardy senna’s, Senna hebecarpa, growing in my food forest
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

  • 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
  • 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.)

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