Many homeowners have spent their time and money to add beauty to their yards, only to watch in horror as the plants in their garden turn from rich green to a sickly yellow color. Most people immediately blame our notoriously poor native soil as the culprit, but in reality, it is how we respond to the soil that does the damage. In most cases the actual problem is over watering, bad drainage, lack of nutrients, high pH or a combination of all of these problems.
San Jose's clay soil is very compact and alkaline (high in pH) by its very nature. Most soils should be conditioned with soil amendments such as Bumper Crop or Gardener & Bloome Planting Mix at the time of planting for better drainage and to help ease soil compaction. By creating a larger planting hole filled with a mixture of native soil and amendments, plants have a better chance of getting established. This enables their roots to develop enough strength to penetrate the harder surrounding soil. After planting, a biannual application of gypsum soil booster will help keep the soil conditioned.
To help plants get established quicker, with less stress, one must learn to water deeply, but infrequently to encourage plants to root deeper and adapt to the native soil. When a plant sits in poorly draining soil that doesn't dry out, the air supply to the roots gets cut off, leading to root rot and eventual death. Soils that are continuously wet also tend to have a bad odor. Unfortunately, when a homeowner sees a plant start to turn yellow, they tend to water it even more, which just make the problem worse. In the winter, consider a half inch of rain or more equivalent to a regular watering.
Over watering also leaches valuable nutrients and minerals out of the soil faster, which leads to chlorosis (yellowing leaves with green veins). This condition can be corrected with consistent feedings (quarterly minimum) of plant fertilizers containing nitrogen to help keep plants healthy and make them grow. Our line of Dr. Earth Organic Fertilizers has a formulation for every plant need and the added beneficial soil microbes in every bag help make the nutrients more readily available to the plant. ( Our Master Nursery brand works well too!)
Sometimes chlorosis can only be corrected with the addition of an iron supplement such as Dr. Iron. Remember, however, that iron will only become activated in soil that has been fertilized with nitrogen first. Most plants tend to prefer neutral or slightly acid (low) pH soils in order to perform well. Because clay soil tends to be on the alkaline side, an application of soil sulfur should be made twice a year also.
All this may sound like a lot of work but the results will more than justify the effort made. The more you put into your soil, the more you'll get out of it.
Matt Lepow, Owner, CCNPro, B.S. Ornamental Horticulture