Claire,

Certain plants, mostly legumes (bean family), can convert atmospheric nitrogen gas to a form of nitrogen that is useful as a fertilizer. The conversion is actually accomplished by microbes (bacteria, I think) that live in nodules on the roots of the plants. The innoculum you received probably came with a legume such as prairie clover. The innoculum contains live microbes that will grow with the plants and fix nitrogen, which the plants then use to grow. I assume that the plants provide something in return, but I'm a little rusty on the subject. The innoculum won't have any impact on plants that cannot fix nitrogen. You may recall from science class that nitrogen gas (N2) is the most abundant gas in the atmosphere, but it cannot be absorbed by plants, and that nitrogen compounds are amoung the most vital fertilizers for plant growth.

I think that even without you adding innoculum to the soil, the plants would eventually find suitable microbes to inhabit their root nodules, but innoculum helps thing happen sooner. I think that most nitrogen fixing plants could live without microbes, but would grow more slowly because they couldn't fix nitrogen.

Ladyslppr.....Thank you for your description, made a lot of sense and definitely given me a slightly better insight. The Innoculum came with the White False Indigo, which I think said legume on the packet. Now, if this stuff helps fix nitrogen into the soil then would it be beneficial to add it say like a fertizler?? Sound like I need to do some research into nitrogen fixing and legumes!

The innoculum is typically a mycorrhizae that creates a symbiotic relationship between fungus in the soil and the roots of the plant. This relationship increases the legumes ability to uptake nutrients, from the soil. The fungus takes in carbon and other nutrients from the soil and converts it to usuable nutrients for the plant roots. In exchange the fungus recieves nitrogen from the plant. This is how legumes "fix nitrogen" into the soil.

Nitrogen fixing bacteria and mycorrhizal fungi are not the same thing, but both are important for many native plants. Legumes (bean family plants) can "fix" atmospheric nitrogen, which means they can convert nitrogen gas into a form useable by plants, with the help of bacteria of the genus Rhizobium (dont quote me on the bacterial name, please). These bacteria can live in the soil without infecting a plant, but I don't think they can fix nitrogen until they infect the roots of a suitable plant. I use the word infect because I think that it the proper term, but you shouldn't assume that this type of infection is harmful. In fact the plants' roots grow structures that enable the bacteria to enter and grow in the roots, and the plants benefit from the arrangement by getting the fixed nitrogen. If you receive innoculum with legume seeds you're receiving nitrgen fixing bacteria.

Micorrhizal fungi are soil fungi that "infect" plant roots in a manner somewhat similar to the rhizobium bacteria, but extend outside of the roots they infect. Micorrhizal fungi assist plants in the way JoePyeweed explained - they have lots of fine root-like filaments that allow them to obtain a lot of nutrients, and they "share" the nutrients with the plants. Apparently miccorhizal fungi are a major component of many native plant communities, and at least partly explain why intact native plant communities can (sometimes) resist invasion by weedy plant species.

Lady, we can quote you (spot on; R.leguminosarum to be exact). But aren't both types mycorhizii? Our Rhizobium is endomorphic mycorhizii and the other type is ectomorphic mycorhizii...

Your namesake flower actually waits for a fungus to infect its seed and then paratizes the fungus (it lacks an energy source of it's own). If the humidity or ph falls out of range, then the fungus can parasitize the seed. LOVE to know what we call that fungus...