This Week in the Garden: Soil health is key to successful gardening

How successful was your garden this summer? Were the plants healthy and vigorous? Was the harvest all you hoped for? If some plants were struck by disease or pests, or just never grew properly, it is time to think about improving the health of your soil.

Experienced gardeners know that well-nourished vigorous plants are better able to fight off disease and pest attacks. With the possible exception of some herbs, most edible plants benefit from plenty of organic matter in the soil. With all soil types, the advice is to work in generous amounts of humus, in the form of manures, vegetation or finished compost. And autumn is the easiest time to add organic matter, as your garden winds down and summer vegetable plants are removed.

Don’t confuse fertilizers with organic matter. While fertilizers, either organic or otherwise, add essential nutrients, most do little for the structure and texture of the soil. They have a valid place in our gardens but they don’t improve the water holding capacity, good drainage and tilth (physical condition of soil, especially its suitability for planting or growing a crop.)

If you have compost piles, you can create some of what your soil needs, but many gardeners find that they cannot produce enough compost to cover their beds as generously as needed. (It is nearly impossible to add too much organic matter because it rapidly decays over the growing season.) If you can’t make as much as you need, compost and composted manures can be purchased in bulk or in bags. If cost is a factor, or if you prefer to use only local materials, check the Organic Materials Exchange at omexchange.org/ for free or inexpensive sources of manure and compost. (Since the pandemic began, this site has listed far fewer sources. Hopefully it will eventually once again offer more choices.)

While it is said that you can safely add fresh manure to your compost bins, the usual advice is not to use uncomposted manure directly on your soil to avoid burning your plants. My experience has been that if fresh manure is spread now, while the garden is fallow, no damage occurs. (If you are fortunate enough to have access to llama manure, it is known to be safe to use around plants right after it is produced, and it has the added advantage of having very little odor.) Regardless, however, manure must be collected and transported, and then spread over your garden, then eventually turned in, and some gardeners will find the work a bit daunting.

So how can you easily and inexpensively add organic matter? A time-honored method is to plant a green manure (cover crop) in the fall to grow over the winter months.Green manure consists of plants grown for the purpose of digging them in and allowing them to decay where they were grown. Legumes are especially prized because nodules on their roots fix atmospheric nitrogen in the soil, making it available to other plants. Clover, fava beans, bell beans and vetch are the most commonly used legumes in the Santa Cruz area. Also often used are annual rye and other grasses. All thrive in our mild winters. They all decay quickly if cut back and then turned in while still young and succulent. Most soils will be ready for planting six weeks after the green manure crop is dug in. If your green manure is planted now and grown over the winter, your soil will be ready for spring planting by the time the rains taper off and you are ready to put in spring vegetables or flowers.

Legumes and other seeds sold in bulk for cover crops are available at local garden centers. Renee’s Garden Seeds offers several packaged blends suitable as green manures. For a how-to video, see groworganic.com/blogs/videos/cover-crops-for-the-garden on details about growing green manures. And if you’d like to plant natives to fix nitrogen in your soil in addition to cover cropping, find a list of appropriate plants at laspilitas.com/advanced/nitrogen-fixing-roots.html.

Soil abundant in organic material is the ticket to a healthy vigorous garden!

Garden tips are provided courtesy of horticulturist Sharon Hull of the San Lorenzo Garden Center.