Many gardeners that swear by square foot gardening use Mel's mix: 1/3 vermiculite, 1/3 peat moss, and 1/3 compost. This mix is incredibly nutrient rich and allows for very intensive planting. Depending on what you want to do, 3 part soil can also include sand, perlite, garden soil, mulch and any number of fertilizers. Since we don't swear by anything other than trial and error, we've made adjustments to our mix in our garden almost every planting season. How do we measure our success? The success of the plants, by the amount of worms in the soil, and giving it the good ol' squeeze and poke test.
We started out with native dirt. Ours is mostly clay and sand, which technically make up loam, but devoid of nutrients as much of the fill dirt is in a developed area, we needed to add amendments. Early on we added organic potting soil, various composts and mulch mixes and had decent results. More recently we've added rabbit manure, compost and a bit more native dirt to round out the tilth, or consistency.
We do let our soil rest a week or two between removing the last harvest and sowing the new seeds. I'm convinced this helps the soil replenish some of the lost nutrients and because we still water it every day, it keeps the moisture in the soil and worms happy. Jeremy says it gives the natural (and beneficial) bacteria in the soil time to multiply after we get done tearing up their home too. Crop rotation can have many benefits in the garden, but it will not restore nutrients to the soil unless you grow plants called nitrogen fixers. What crop rotation does do is reduce the risk of using up specific nutrients from repeated planting. Essentially don't plant the same plants in the same place. This is a method used to help eliminate pests as well. We've dismissed the practive of crop rotation due to space constraints, sun limitations and because we turn our soil and add amendments every season before we plant. For someone with more space and less time, crop rotation may be a good idea.
Before you start growing, it is always a good idea to test what type of soil you have. There are several ways of doing this in addition to sending a sample to a lab for examination. We recommend the Soil Squeeze and Poke Test or the Ribbon Test for 2 reasons: both require you to get your hands in the dirt and are easy to do.
The Soil Squeeze and Poke Test: Take a handful of moist soil and squeeze it. Open your hand and immediately poke it with one finger. The soil should crumble for a great consistency. Not there yet? Don't worry, it takes time! If it falls apart as soon as your hand opens your soil is too sandy. If it sticks together and you have a finger indentation, you have clay soil. With both of these deficiencies, adding amendments such as compost and other organic matter like peat moss or coconut coir will improve the soil and nutrient levels. Dependng on your preference, vermiculite, perlite or ground pumice are also options for improving sandy soil and clay soil into more desirable loam when added with compost and organic matter.
The Ribbon Test: Grab a handful of moist soil and squeeze it out of your hand using your thumb and forefinger. If it falls off as it leaves your hand, the soil is too sandy. If it hangs from your hand after an inch, it has too much clay. Any place between that and you have a loam mixture which is what you want.
While these two tests are good for identifyiing the soil type you have, they will do nothing to show nutrient content or pH, both of which are just as important. Soil tests sold at nurseries and gardening stores are what you will need for more in depth results. There are also laboratories that test soil samples and are able to give you a report on the quality and nutrient content.
Most plants like a slightly acidic soil pH because it assists with the absorption of nutrients. We have found that the more variety amendments you can add, the better the soil will be able to maintain a healthy pH. Keeping a good balance of materials in your compost is also key because what you put into your compost will invariably end up in the soil if you use it.
Very few plants prefer an alkaline environment. Here in California not only do we have to combat the natural alkaline soil, but our water is usually filled with calcium, magnesium and chlorine, and often flouride as well. Calcium and magnesium are both required nutrient elements for plants, but in smaller amounts. Chlorine and flouride are basically poisons so imagine how your plants might feel if they have to combat that as well as alkaline soil. An easy way to avoid giving your plants too much of these chemicals is to set out the water the day before and let them evaporate out of the water. I want to mention again that gardening centers and nurseries should have soil testing kits so you can check your soil yourself and make adjustments. We have never actually tested our soil, but we follow the rule of keeping plenty of variety in our amendments which has worked for us so far.
Pay attention to your zone. In Southern California sometimes we are zone 10, sometimes 9B. While the 14 zone maps are useful, they don't take into account micro-climates due to topography which can have a big impact on temperatures. Sunset offers even more in depth 24 zone information on their website, but even the map is still a generalization of your climate. Check your own yard for hot and cold areas that you can use for different plants.
We don't have a go-to seed company, or specific plant varieties that we grow. We might have a conversation about what we'd like to grow and then purchase seeds at our local farm supply store or order them online. We do buy organic seeds when we can, and of course ones that grow well in our area. Be mindful of what seeds grow well in your area by choosing plants by season and noting the type of soil they grow well in. Keep a log of your garden so you know what works and what doesn't. Always be sure to experiment as well. Sometimes a plant may just need to be moved to a different part of your yard for less or more sunlight. The bottom line when choosing seeds is grow what you want to eat.
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