Your garden needs to eat, just like you do. And just like how you track carbohydrates, protein, and fat, your plants need a specific breakdown of nutrients, too. That’s where NPK – nitrogen, phosphorus, and potassium – comes in. While plant nutrients are found in nature, each garden’s plot of soil can vary. So, garden products will often come with these nutrients already in perfect proportions for what you’re growing.

What Does NPK Stand For?

If our food is comprised of three main nutrients, you can bet that your plants’ food is, too. And just as each of those nutrients has specific functions for fueling our bodies, the soil’s nutrients also have their own responsibilities in supporting a garden’s health.

N: Nitrogen

Nitrogen is responsible for growth of leaves and greenness of a plant.

Within the ratio, N stands for nitrogen. This is the naturally-occurring element that makes up a large part of the air we breathe. But the nitrogen in the air isn’t enough to feed our plants, so we rely on organic matter and garden products to provide enough of this nutrient from the roots up. Nitrogen is responsible for the growth of leaves on a plant. In fact, you may be able to diagnose a nitrogen deficiency with yellowing leaves and skinny stalks. Nitrogen also helps plants create chlorophyll, a green pigment in plants that allows for the absorption of sunlight into photosynthesis. Green plants and vegetables typically have higher nitrogen requirements.

P: Phosphorus

Phosphorus encourages strong roots, fruiting, and flower development.

Another vital nutrient in a plant’s growth is phosphorus. It helps to convert other nutrients into usable building blocks by developing a plant’s root system. It typically affects a plant’s ability to flower or fruit and is known as the “bloom booster.” That said, you may notice a phosphorus deficiency when plants:

  • Are smaller than they should be
  • Produce little (or no) flowers
  • Have weak root systems
  • Appear to have a purple tint

Plants that fruit or produce blooms are more likely to need higher phosphorus levels, and the best time to apply phosphorus to the garden is early spring before you’d expect blooms to occur. Phosphorus garden products can come in both organic and synthetic versions, though. When it comes to synthetic phosphorus, be wary of it leaching into your water supply and creating a heavy salt buildup.

K: Potassium

Potassium helps the general health and hardiness of a plant. It typically promotes growth and large fruits.

While not exactly intuitive, “K” is the symbol for potassium, which is the third macronutrient that your plants depend on. Potassium helps the plant perform overall. It strengthens the cell to increase disease resistance, promote growth and durability, and create a larger fruit set. While phosphorus is responsible for increased blooms, potassium can help increase the size of that bloom – especially helpful in growing fruit. Potassium is a primary reason forest fires can be beneficial, as the formation of wood ash can unlock potassium and renew the area’s life. Providing this nutrient to your plants helps to make them hardier against external elements, from the weather to pests. While it’s hard to identify a potassium-deficiency, yellowing edges, leaves curling downward, and susceptibility to disease can all be indicators that you should add potassium to your garden.

NPK: A Buffet for Your Plants

While nitrogen, phosphorus, and potassium are integral in any plant’s vitality, different plants require different NPK ratios. Many garden products specify which varieties they’re suited for (i.e. knock out roses or berries). Typically, general purpose fertilizers contain equal amounts of each nutrient, or in some cases very similar (ex. 12-8-6). They are formulated to meet most general needs for most plants throughout the entire growing season. Helpful for your entire garden, general purpose fertilizers may not always work for your specific needs.

Enter: special-purpose fertilizers. These focus on the specific nutrient ratios that your plants may need. There are three main types of special-purpose fertilizers:

  1. Nitrogen-heavy formulas work best for periods of active growth – usually in early spring – to encourage lush growth and greenery.
  2. Higher levels of phosphorous and potassium stimulate root growth and flowering/fruiting. These are applied at different times, but typically at the start of blooming season.
  3. Varying ratios of nutrients can be formulated based on a specific plant variety and its needs.

Regardless of which type of fertilizer you choose, follow the package’s application instructions for frequency and amounts needed. There are many options, from granular fertilizers to spikes, so choose the delivery method that best works for your – and your garden’s – needs.

Your Soil, But Better

Each of the three NPK macronutrients can be found in soil. The problem is that very rarely is our backyard soil in the best condition for optimal plant growth. Many factors can affect our soil health, ranging from the weather to its natural geography. But, in general, it’s safe to say that no soil will provide enough – or the right mix – of nutrients to our plants. That’s where fertilizers come in. And there are a number of options that you as a gardener have, including several pre-packaged mixes (also called “complete” fertilizers) and soil amendments (called “incomplete” fertilizers).

Complete Fertilizers

Complete fertilizers contain all three NPK nutrients. They are off-the-shelf products that work on their own to provide your plants with the food they need, making fertilizing easy. With perfectly proportioned NPKs and none of the math, they’re a one-size-fits-all solution for any plant type you have.

Incomplete Fertilizers

Soil amendments are recommended for more advanced gardeners because they only contain one or two of the three major nutrients; thus, they’re not a comprehensive product. These can be useful for the gardener who wants to formulate their own mix of nutrients or use what their soil already has to offer. To find out which soil amendments you need, we recommend getting your soil tested by your local county extension office to get a good idea of what ratios your soil already contains. From there, you can identify whether you need more nitrogen, phosphorus, or potassium, and therefore, which amendment will work for you.

For a quick reference, blood meal is a nitrogen supplement and Jobe’s Organics bone meal is a source of organic phosphorus. Compost is also a popular soil amendment that provides long-term benefits, but do not help immediate soil nutrient needs. By using soil amendments, you can have more control as a gardener over which products go into your garden and which nutrient ratios you want for each flower bed.

Reading NPK

2-5-3: 2 percent nitrogen, 5 percent phosphorus, 3 percent potassium.

NPK is an important tool for gardeners, but how do you know what you’re getting? Most fertilizers are aptly named (“Jobe’s Bloom Liquid Fertilizer,” “Jobe’s Organics Fast Start Granular Fertilizer,” etc.), so a good rule of thumb is to follow the packaging. But if you’re looking for the exact ratios, fertilizer products also contain a set of three numbers offset by dashes. These numbers represent the percentage of each macronutrient that’s present in the product. They always follow the order of nitrogen first, then phosphorus, and last potassium – hence, NPK.

Fertilizing Made Easy

No matter your garden goals or plant varieties, at Jobe’s we offer a range of fertilizers in both synthetic and organic forms. When your existing soil nutrient levels are not sufficient to produce big, beautiful blooms and strong roots, trust the Jobe’s line of products. With both plant and nutrient-specific products, we can help. Find the fertilizer product your garden needs today.

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