One of the main goals we had when developing the newsletters we send out monthly is to provide guidance and assistance to those who want to provide the best care and see the best results from their trees and landscapes. In this month’s newsletter we want to make sure you are using a very important tool available to the home gardener and landscape manager. Whether it’s a few small blueberry bushes at your home or a couple hundred year old oak trees, this tool can transform appearance and lengthen the life of your plants. This special tool is called fertilizer. Today in the garden community fertilizer can be considered a bad word, but we believe it can be a great asset when used correctly. Our hope is that we can provide clarity on the importance of fertilizer, what products are available, and how to start applying it this month.
The reason why we have chosen to discuss fertilizer this month is because this is the time to apply it. Between February-March are the ideal spring times to apply.
To get started, let’s first understand why it is so important to apply in the urban garden.
3 Fertilizer Fundamentals
1. The Importance Of Fertilizer
I always wondered why fertilizer was so important if all the trees in the forest and mountain seem to be so healthy and vigorous without ever needing pruning, regular watering, or annual fertilizer plans. After understanding the difference with the environments in the urban landscape versus the natural landscapes of undisturbed mountains or pastures, it became very clear.
Here are some reasons:
SOILS
In the mountains or natural landscapes of California the soil has been undisturbed. The soil is not compacted by heavy equipment and tractors driving over the soil when homes or communities are being built, the soil has not been excavated to several ft in depth and replaced with non native soil, the layers developed over years of plant decomposition have been left untouched, and the microorganisms in the native soils are not thriving in a foreign environment. We add chlorine to our soils from our pools, we add high levels of toxic elements from recycled water, and various other things that can damage soils. In the urban landscape the soils are damaged as a result of these practices.
ORGANIC MATTER
As a result of the damaged soils in the urban environment, the organic layers and matter are often depleted or sparse. When trees and plants shed their leaves it decomposes and provides nutrients to the soil for the plant roots to absorb. This process enriches the soil, provides an environment where beneficial organisms can thrive, and adds nutrients to the soil for the plants to use for growth and nourishment. Over the years this layer in the upper few inches of the soil becomes one of the main sources of nutrition for the trees and plants in the landscapes.
NUTRIENTS
In order for plants and trees to grow and thrive they need nutrients in the right amounts and the correct soil PH levels so that they can be absorbed by the roots. In the urban landscape this often needs to be created rather than expected to occur naturally as a result of the issues identified above. Plants need a combination of macro and micro nutrients. When they do not have them in the right quantities it can affect their appearance, ability to grow, their defense against pests and disease is weakened, and could eventually die.
2. What Are My Options?
The goal is to create an environment where the plant roots and soil organisms will thrive in. This often looks like recreating the environment found in nature. Our approach to enhancing soils is a hybrid process of using organic and inorganic components. Here are some practical ways you can start improving your soils and feeding your plants:
The first step is to understand your soil before attempting to correct it.
Here are some important things to consider:
- What type of soil do I have? Clay, silt, loam?
- Does my soil have an organic layer at all?
- Has my soil been compacted?
- Perform a soil test to determine the PH levels and also if there are low or high amounts of certain nutrients in the soils.
- Understand what nutrient and PH levels your specific plants prefer.
Once you have that information then you can work on making adjustments to the soil:
Now that you know what nutrients are lacking you can apply them to the soil. There are many different methods of applying them:
ORGANIC:
This is often accomplished by using manure, compost, bone meal, fish emulsion, etc. These are great options and offer great conditions for soil organisms, soil composition, and long term provision of nutrients. Some issues with these methods are that the quantities applied are very challenging to measure, it takes longer for the nutrients to be available to the plants, and a lot of material can be needed to treat large areas.
INORGANIC:
This would be applying commercial fabricated fertilizers. Some of these can also contain chemicals, but the vast majority are simply isolated nutrients placed in a casing that are activated by moisture. These can be applied in several ways:
- Granular Fertilizer: This is often a slow release and can be mixed into the soil of the plants or trees.
- Water Soluble: this is mixed into water and poured or injected into the soil. This is fast acting method and highly effective.
- Liquid: Fertilizer can be poured around the roots or sprayed onto the leaves in a liquid form.
3. How To Apply A Granular Fertilizer To My Garden
- Move the mulch or rock out of the drip line of the plant so you have bare soil
- Loosen up the soil carefully to a depth of 2-3”.
- Apply the fertilizer evenly under the entire spread of the canopy. We call it the drip line.
- Place the mulch or rock back over the area
- Water the fertilizer into the soil
Our recommended method of improving the soils in your landscapes: This method can be applied to plants, shrubs, and trees.
- Aerate soil to improve pore space and reduce compaction
- Add organic matter or compost to improve the soil composition
- Add mycorrhizal fungi to the soils (https://extension.umn.edu/yard-and-garden-news/should-you-add-microbial-soil-amendments-your-garden)
- Apply the needed amounts of fertilizer to the soils based on your plants specific needs
- Adjust the PH levels that are best suited for your plants or trees
- Add several inches of organic mulch over the soil to improve the organic layer and add nutrients to the soil over time as the mulch decomposes.
We see this as a hybrid method to improve plant health and environmental conditions quickly and also make adjustments that will last many years.
Here is a list of common questions we have been asked that may assist you with beginning to apply fertilizers in your landscape:
What type of fertilizer should I use?
The most common is a granular product. It’s a safe option because it is slow release. Most any type will work; it just depends on how fast you need it to work and what the goal is.
Where do I buy these fertilizers?
They can be purchased at hardware stores and local nurseries.
How do I apply fertilizer?
The bag or box the fertilizer comes in usually has directions on how to apply. Most important is to apply the correct amounts at the correct locations. Don’t just put it all in one spot. Spread it evenly under the canopy of the plant. Mix it into the soil.
Can I apply the same type of fertilizer to all my plants?
Many plants prefer special blends of fertilizers. Flowering plants prefer higher phosphorus, evergreens prefer higher nitrogen, etc.
How often should I fertilize?
The best times to fertilize are fall and spring.