Mario Bautista
Hopefully the high temperatures are behind us, and fall is on the way.
I often look at nighttime temperatures instead of daytime to determine fall. When nighttime lows regularity are in the 50s, I considered it fall.
Fall is the time of year to accomplish many gardening or landscaping projects. One is fertilizing your plants.
Our landscape plants should be fertilized now with fertilizers that are lower in nitrogen and higher in phosphorus and potassium. We need to avoid using fertilizer that has only nitrogen. Using too much high-nitrogen fertilizer now can make the plants grow too new leaves and branches. This new growth can be easily killed by the first frost of the season.
We are trying to make our plants slow down their growth and be prepared for winter. I like to use triple 15 (15-15-15) or triple 16 (16-16-16), in the late spring and early fall. On a bag of fertilizer, the first number is the percent of nitrogen, the second number is the percent of phosphorus and the last number is the percentage of potassium in the bag. Triple 15 or 16 is a fertilizer that has the same amount of nitrogen, phosphorus and potassium. Even though the percentage of nitrogen looks high, it is in a way diluted by the phosphorus and potassium.
Nitrogen in the plant makes amino acids and can cause the plants to grow. Phosphorus is used for the development of roots, flowers, fruit and seeds, which can be just the opposite of nitrogen. Plants have a tendency to either grow branches and leaves or slow down growth and form flowers and fruit. Potassium is used to regulate water in the plant, and it makes the plant more drought-tolerant and disease-resistant.
A late summer fertilizing of your fruit trees is also important. It is usually best to wait until you finish harvesting your crop, before fertilizing. Again, the triple 15 or 16 is a good late summer fertilizer for fruit trees.
Your tomatoes and other summer vegetables will flourish for most of October. A good application of fertilizer for your garden is important to finish out the year. Once again, too much nitrogen will cause your plants to grow and look great, and it will prevent the formation of fruit. So, the triple 15 or 16 is a great way to help your vegetables.
Phosphorus and potassium are nutrients that are slow to move through the soil. We apply them in fall and hope that the winter rains help move them down into the root zone for spring. Phosphorus and potassium applied now will also help plants like roses have a good late-year bloom. Make sure that old, faded blooms are removed.
Other nutrients such as iron, zinc, magnesium and manganese can also be applied now to increase the nutrient level of the soil. These are better applied to the plant than to the soil. Buy them in a liquid chelate form. Spray this fertilizer directly on to the leaves of the plant.
The goal of fall fertilization is to not to encourage growth, but to improve the soil’s nutrient level for spring growth. The exception is cool season lawns, which grow best during this time of year.
Remember that the first number on a bag of fertilizer is the amount of nitrogen, the second is phosphorus and the third is potassium. Applying phosphorus and potassium now allows the nutrients to move through the soil during the winter. Potassium can even help make your plants become hardier towards the cold.
