The soils of California's Central Valley are described as having a xeric soil moisture regime characterized by warm, dry summers and cool, moist winters. As we enter the rainy season in Yolo County, we can relax in our garden-watering duties, but there are a few things that happen in your garden.

To start, soil structure may be in for a wild ride. Picture the soil particles—sand, silt, and clay—locked together like a dance floor at a middle school prom, with microbes as the overenthusiastic chaperones. Now, introduce heavy rain and suddenly it's less “dance floor” and more “mud wrestling pit.” When water saturates soil, pore spaces that normally hold air become overwhelmed. In clayey soils, waterlogging can lead to anaerobic conditions which can be problematic, especially if it lasts. Anaerobic conditions occur when water fills all the pore spaces in the soil, eliminating oxygen and depriving aerobic microbes of their preferred electron receptor, oxygen. In response, some microbes switch to anaerobic respiration, using alternative electron acceptors such as nitrate, sulfate, or carbon dioxide. This process is less efficient and can result in the production of byproducts like methane, hydrogen sulfide, or organic acids, some of which can be toxic to plants and inhibit root growth and function. This can indeed make life tough for plant roots by reducing their access to oxygen and exposing them to potentially harmful compounds.

But not everything in your garden reacts negatively to heavy rain. Some plants eagerly soak up the excess water, extending their roots to absorb every available drop—at least until the water becomes too much and begins to saturate the soil. Personally, I welcome all the rain with open arms after having no rain for five months. I just don't mention it to my succulent collection—they're still trying to dry out from the rain last week, poor things.

Finally, it's worth mentioning what heavy rainfall can mean for soil nutrients. Nutrient leaching is a serious issue. Nitrogen, especially, when added to soils can easily be washed away with excess precipitation, potentially contaminating groundwater or nearby water bodies. To mitigate this, it's crucial to be thoughtful about when and how you apply nutrients, particularly around irrigation events or during the rainy season. Incorporating strategies such as applying mulch or planting a living mulch can help prevent nutrient leaching (as well reduce soil erosion and suppress weeds). Also, timing nutrient additions carefully can help retain nutrients in the soil, preventing them from being washed away by heavy rains.

In summary, while rain can transform our carefully tended plots into waterlogged challenges, with smart planning—like using mulch, timing nutrient applications, and nurturing deep-rooted plants—we can keep our gardens resilient. So, batten down the hatches, protect those succulents, and let's see what lessons the rainy season has for us.