Nitrogen fixing shrubs can serve valuable roles in a permaculture system. Goumi (Elaeagnus multiflora) and Sea Buckthorn (Hippophae rhamnoides) are two examples that also produce flowers and an edible fruit. These shrubs can serve pioneer species and have the ability to stabilize and improve poor soils. Both species are able not only to fix their own nitrogen but are also hardy and able to withstand drought. Spiny versions of both species are available if you intend on using them as living fences. The trimmings from these shrubs can be used as green manures or mulch. Both species are traditionally viewed as medicinal plants and have nutritious qualities ranging from high carotenoid content to healthy levels of omega fatty acids.
There is one flaw inherent to both species which should lead you to consider them before implementation; they are not native. In addition these plants produce viable seeds in fruits that are attractive to birds and other dispersers. Because they are drought resistant and fix their own nitrogen, they are aggressive and resilient growers. All of these factors make them potential invasive species.
Regarding any non-native you should always take precautions regarding the unwanted spread of seeds. A timely harvest, bird nets, scare crows, trained dogs, etc. are key elements of containment. Be sure to scout areas near your farm for escaped individuals just in case. Dig up any escapees and bring them home and/or destroy them. Some species are great on your farm but don’t belong in the wild; other species occupy the niche these species would invade (that’s something to think about the next time you see a new subdivision).
So how does one determine whether or not a non-native plant is worth planting? First, consider whether there is a native alternative. Concerning these species, Silver Buffaloberry (Shepherdia argentea) was an option. Buffaloberry fixes nitrogen, is hardy, is drought tolerant, produces an edible berry, and has thorns.
In the end, I planted all three species. Having all three species meant three different periods of flowers and fruit. Because the three species were distantly related they helped add genetic diversification to my nitrogen fixing shrubs. Choice of cultivar was important when I made my decision e.g. an astringent or sour goumi variety would not have been worth the compromise. Choosing superior cultivars increased both the resilience of my specimens and their edibility. Unfortunately, such choices are often not available with natives e.g. silver buffaloberry. Let’s hope that natives become more popular and available in the future.