by Mark Levisay

I’m going to take a break from talking about plants and shift focus to fertilizers and soil additives. The Corner Store Garden Center carries an extensive line of Espoma products that you don’t know about since you can’t come inside the greenhouse and see them all lined up! That’s a shame, because many of these products could prove useful to you during the garden season. I took my camera (and mask) up to the greenhouse one afternoon and photographed each product’s bag, front and back, so you could see what you’re missing. I’ll try to explain what’s in each product and what it can do for your garden.

Fertilizer for acid-loving plants

Holly Tone is an organic, balanced fertilizer with an N-P-K analysis of 4-3-4. It also contains 3% calcium (Ca), 1% magnesium (Mg) and 5% sulfur (S). The sulfur component is the key here, as this product will act to raise the acidity of the soil where it’s used.

Espoma’s “Bio-Tone” provides beneficial bacteria

You’ll also notice as you look at the side panel of the bag that it contains 3 types of bacteria. Healthy soil contains a mix of both bacteria and fungus, and these organisms are critical in breaking down chemical compounds into forms the plant can absorb. Adding these beneficial bacteria to your soil will improve the overall “biome” and help plants thrive. All of Espoma’s xxx-Tone fertilizers will have this “Bio-Tone” component. A side effect of this is that each package will have a “use by” date, as these bacteria colonies will slowly decline over time.

Another thing you’ll notice on the package is the source of the water-insoluble nitrogen (N). This in-soluble nitrogen needs to be broken down by organisms in the soil to be available to the plant, so it’s considered slow release. Feather meal, bone meal and poultry manure are all by-products of chicken and egg production, and alfalfa meal is derived from a common farm crop. It’s great that these by-products can be used as fertilizer and they also help improve the tilth of heavy soils. An unfortunate side-effect is that our dogs think this stuff is candy and we can only use it in areas where the dogs are fenced out!

Ingredients panel for Espoma’s Holly-Tone organic fertilizer.

Plants and application

There are a number of plants that benefit from growing in acidic soil conditions. Evergreen trees and shrubs, azaleas, rhododendrons and mountain laurels, and blueberries and other bramble berries come to mind. For a more complete list go to espoma.com for additional information. They have good lists of plants that benefit and application instructions.

Espoma recommends a spring application and a smaller fall application for shrubs and two separate spring applications for berries. To be sure for individual plant varieties I’d refer to Virginia Cooperative Extension’s website (ext.vt.edu) as they have loads of information on the nutritional requirements for most garden plants.

Next time we’ll talk about Plant Tone, which is an organic fertilizer I have used a lot in my vegetable garden with great results.

Have a garden question? Send me an email at marklevisay@gmail.com.

by Mark Levisay

You’ve probably seen bags of 10-10-10 “plant food” at a big box store or garden center and may have wondered what those numbers mean. The numbers refer to the percentage by weight of N-P-K, or nitrogen, phosphorus, and potash (potassium) which are essential nutrients that plants need to grow. Rather than thinking of them as plant “food,” it’s helpful to view them as ingredients that the plant uses, along with sunlight, to manufacture food (sugars) that the plant needs to live. Let’s talk about those ingredients in a little more detail.

A little chemistry

Carbon, oxygen and hydrogen are readily available to the plant from the air and water (CO2 and H2O), but the nitrogen in the air is tightly bound up as N2 molecules and can’t be accessed by plants. Phosphorus (P) and potassium (K) are minerals that would usually be found in soil. These six elements are considered the major macronutrients plants need for growth. Calcium (Ca), magnesium (Mg) and sulfur (S) are minor macronutrients and might be lacking in some soils. Micronutrients are iron (Fe), zinc (Zn), molybdenum (Mb), manganese (Mn), boron (Bo), copper (Cu), cobalt (Co) and Chlorine (Cl). Most of these will be found in soil in adequate supplies for plants but can be added if a soil test indicates a deficiency.

The functions of N (Nitrogen), P (Phosphorus) and K (Potash)

The back of the fertilizer bag will provide details on the ingredients.

So, what do these individual nutrients of N-P-K do for the plants? Nitrogen promotes top and leaf growth and is essential to the plant. It’s transient in soil and will need to be added, at least yearly, depending on what plants you’re growing. Phosphorus is important for root growth and fruiting, but stays in the soil, so once added should be OK. This is also the nutrient that promotes algae blooms in Chesapeake Bay, so you’ll rarely see this nutrient in products like lawn fertilizer. Potassium promotes stem durability and cold hardiness and is also transient in soils, so we’ll have to keep up with this over time. A N/K ratio of about 1 is probably right for most average plants.

Soil testing provides your goal

To understand how you can improve your soil and provide your plants with the ingredients they need, you should test. You can guess at what’s in your soil by observing your plant’s growth, but testing will tell you for sure. Your county extension agent can help you learn more. The test results will tell you what’s in your soil currently and make recommendations to improve it for good plant growth. The recommendations will be expressed in pounds of nutrient per 100 or 1000 square feet. The test will also tell you the pH (measure of acidity), but we’ll talk about that in a separate blog.

The pounds of nutrients recommended is where the numbers on the bag come in. In our original example, 10-10-10 tells you there is 10% N-P-K in the bag by weight. A 40 pound bag has 4 pounds each of nitrogen, phosphorus and potassium, or 0.4 pounds per pound of fertilizer. The rest of the bag is an inert filler, which is important because too much nutrient too close to the roots of a plant will burn the roots. Some of the organic fertilizers are less potent, like Espoma’s Plant-Tone organic fertilizer at 5-3-3, so they can be added in larger quantity to the garden.

Watering is very important in relation to fertilizer application, and it’s uptake by the plants. The nutrients in our bag of fertilizer are in the form of nitrates, nitrites, phosphate and potash which break down into charged ions in water. These ions are then available to be absorbed by plant roots. 98% of the plant’s nutrient needs are absorbed in water taken in by the roots. Roots encountering dry particles of fertilizer can be damaged. Adding chemical fertilizers one to two weeks before planting seeds or plants can allow the fertilizer to become mixed in the soil and go into solution. I’ve had pretty good luck using Plant-Tone at planting time since it’s not too strong, but I always water well after planting.

With the right ingredients, your plants will trhive.

To learn more about the individual fertilizer requirements of specific plants, go to the Virginia Cooperative Extension website. You’ll also be able to find information about soil testing on the site.

Have a garden question? Send me an email at marklevisay@gmail.com.