Water is a critical component of gardening in the dry Western USA. It was why I chose my mountain forest, it gets a small amount of rainfall every month. To see your natural rainfall patterns, search online for rainfall charts for your closest town.
From my rainfall charts I could see that my 5 acres gets 16-24 inches of rain per year and that it is spread pretty evenly through the year. Even better, it gets an inch or two extra during the summer growing season. For low rainfall, this is excellent. It is also why my trees survived an 11 year drought fairly intact.
If my soil had more humus, it would grow many more plants. Humus supplies nutrition and more importantly, it holds water for plant roots.
Rocks slow water sluicing downhill. Some of that slowed water seeps into the soil instead of the ditch at the bottom of the hill. The water slows enough to drop its sand and soil load uphill from the rocks.
Although these are natural (free to me) processes across my 5 acre hill, when I am up on the hill I move a few rocks to good spots to catch a bit more water and soil. Even the smallest reservoir of sandy soil with a bit of clay in it will sprout a wildflower. Wildflowers feed the birds, butterflies, and bees for sure. They also give cover to lizards who eat the insects that are attracted, and make pretty for me. The right types of wildflowers make winter teas.
A different niche these flowers fill is soil stabilization and water retention on bare rock hillsides. Once the flower sprouts, its roots stabilize its little patch of soil and hold it in the next rain. It slows the water sluice and captures it’s own water supply plus the small amount of sand and clay in the water. This creates a gentle fertilization that arrives with wate and does not damage soil biota. Chemical fertilizers can burn plants but always burn the soil biota that support plant life.
Plant roots do one more thing, they grow quickly when it rains, pulling up as much water as they can; however, when the soil dries the small roots die back and decompose in the soil. When the soil is moist again, the roots grow quickly into the same spaces, easier each time, and pull water up. As this process occurs over and over, the plant gets a nutrition boost from its old roots. The energy expended to reach water each time is not lost, but is recycled back into the plant.
I love all the circular economies in nature.
I have a lot of these small dramas on my hill in different stages of development. There is always a new bit of detritus on the uphill side of brave plant pioneers. These first pioneers keep building soil and conserving water until a sumac seed arrives. The sumac sends it’s roots into the moist richness held by the wildflower and shoots up to take its light as well. Some flowers die back, but most stay and keep growing. The two compete but they support each other as well. Even though the Sumac took initial nourishment from the wildflower it soon improves the stability of both.
The sumac uses the same strategies as the wildflower, slowing the water sluice during rains and capturing sand, clay, and detritus lost by plants uphill. Next a juniper berry arrives and takes the water and nutrients built up from the wildflower and sumac. It’s roots can go down over 100 feet and it brings water all the way back to the surface. In my Food Forest, the Pinyon Pine is usually the last arrival and it uses the juniper as a nursery plant. It sprouts downwind and is protected by the juniper. It’s roots shoot down into dead root cavities and gains water and nourishment from the juniper’s prior work.
All of these stages are on my bare swathe, created by a bulldozer a couple decades ago. Each of these small ecosystems are amazingly complete and stable once the pinyon pine arrives. They are the most essential tree guild of my Food Forest, and the oak arrives after the pinyon. Each addition comes after the initial four.
As much as I disliked that narrow swath from the bulldozer, it gives me a window to understand how my essential tree guild forms and becomes a Food Forest in my circular economy. As they link to each other and to the forest, they provide a firmer web. A single wildflower out on a rock dies easily in a hot spell or drought. Once it has even a sumac bush it is more likely to get through. Oak and other important species come afterward and are all stabilized by the pioneers.
All this from a rock or three slowing water down long enough to sprout a wildflower seed.