California Soil + California Natives

Native soil literacy can be difficult for beginners, especially folks coming to natives from a more traditional gardening background.  The two main things to remember are 1) soil is a living system and 2) native soil is GOOD soil, and yes- that includes your hard, heavy clay!

Soils are either bacteria dominant or mycorrhiza dominant, meaning that the plants that grow in them are closely intertwined and often coevolved with these bacterial or fungal communities.  Our soils in California, when in good condition, are mycorrhiza dominant,  and that’s a big part of the magic of how native plants work in all their fantastic, drought tolerant ways.  The roots of natives and mycorrhizae in the soil make a great team– root hairs are often replaced by fungal mycelium that attach to roots due to their ability to increase drought tolerance and resiliency.  Because mycelium (feathery, root-like filaments made of hyphae that fungi produce underground) are finer than actual root hairs and therefore take up less space than them underground, fungal dominance and fungal connections with native roots allows for there to be more room underground for soil, which retains the water that is then available for plants to intake. 

This is not to say that bacteria doesn’t play a role in healthy native soil at all– it definitely does!  Remember, it’s not about total absence of bacteria, it’s about dominance of mycorrhizae.  The fungi and plant roots enter a dynamic where each system emits chemical signals telling the other to grow more and vice versa.  Bacteria is a part of this cycle as well, and healthy organisms will join the signaling party and emit their own chemicals to encourage growth of the others.  

So how do we steward these microscopic soil denizens and how do we discern between “healthy” ones and not so healthy ones?  Well, first and foremost: spending a bunch of money on fancy amendments is not the answer.  If I had a dollar for everytime someone asked me what they should do to “fix” their “super crappy clay soil”, I’d have a lot of dollars.  Which makes me so sad!  The way our plants grow– that whole photosynthesis and collaborating with living soils thing–is designed really well.  And spoiler alert: clay soil is a big part of that magic.  When clay gets saturated it stays wet for a long time, it also is able to hold onto nutrients.  This is how our plants are able to do a lot with a little rain.  It’s also why, especially in the summer when it’s really hot out, excessive watering often kills natives because that heat and moisture combo is the perfect breeding ground for bacteria, which tips the mycorrhiza-bacteria scales and can lead to issues like root rot, etc.  Most folks in the greater Los Angeles area have either clay or sandy loam.  The best method to find out more about your soil is to dig a hole, fill it with water and see how long it takes to drain.  If the water drains really slowly, you’ve probably got more clay, if it’s very speedy you’ve probably got more sand.  This also gives you information about how much and how often you’ll need to water going forward.

In regards to the chemical signaling mentioned earlier, simply weeding your site, planting natives and mulching around them is the main method to either help stabilize or move towards thriving, active soils where that behavior is going on.  Mulches can be either organic materials (a plant’s own leaf litter, cedar mulch like the one we sell, etc) or inorganic materials (gravel, rocks, etc.).  Different plants like different mulches– oaks need their oak duff to survive, desert plants are rock eaters since they like to hang out in washes and lean soils, chaparral and woodland plants usually like an organic mulch paired with some boulders, just think about what you see going on when you’re out on a hike.  There’s no need to get super high tech, fixate on manipulating your soil pH or break your back doing intensive tilling.  Many ruderal and invasive plants do not have compatible relationships with beneficial native mycorrhizae in our soils, often depleting and exploiting the nutrients and moisture they have produced and accumulated, which are essential for flourishing native ecology.  They can even suppress mycorrhizal growth and kill these networks as they proliferate.  This is why tilting the scales back, working to get rid of weeds, and establishing natives to a point where they can outcompete and suppress the growth of plants like these can be a slow, challenging process, especially at highly disturbed sites. Examples of highly disturbed sites include: longtime agricultural plots,  areas that have burned too hot and too frequently, places with heavy human usage/impact etc.  And while this talk of mycorrhizae may have you thinking you need to go buy fungal inoculants for your soils, most of the ones on the market don’t contain native species and don’t make notable differences for the plants.  An interesting tidbit for your back pocket is that a lot of our growers here in SoCal have their own proprietary soil mixes/growing mediums that often include mycorrhizae in them.  That’s why there are sometimes little mushrooms growing in our pots during the rainy season.  So, all in all, it’s the same sort of deal with the fungi as it is with the insects and critters– if you build it they will come, proliferate and hopefully thrive!  There is truly so much to say on this topic, and a lot of very smart people have written very long books, but hopefully this primer helps you look at the ground beneath you a little differently.  Native plants love native soil and while there are definitely special scenarios where more serious methods are necessary, most of the paths leading to healthy soil just involve patience and TLC.