Fertilizer 101
Why Plants Need Fertilizer
Everything grows better when it’s got the right nutrition, and that includes plants! Plants absorb nutrients that are found in the soil and water in order to grow. If there aren’t enough to meet their needs, it can affect their overall health and you’ll end up with plants that have weak stems, smaller leaves, fewer flowers, and poor colour. Booooooo!
Providing extra or missing food to your plants is often referred to as providing fertilizer. There is a great big world of fertilizers out there, and it can be a touch overwhelming when you’re starting out (heck, even if you’ve been doing it for a while there is always something new to learn!)! So let’s dive in and break it down, and help you learn how to help your plants be the best they can be!
What IS Fertilizer Exactly?
Fertilizers can be natural or artificial, and contain elements to enhance the fertility of the soil, or to replace elements that were already used up by a previous plant/crop that used the same soil.
There are about 17 essential nutrients that plants need to survive, but some are only needed in small quantities and you don’t have to worry about them. Most of the time, you only need to be concerned with the Big Three (nitrogen, phosphorus and potassium). These are called the primary or macro nutrients.
Nitrogen (N):
Is super important for plant metabolism, growth and health. It’s a building block for growing new stems and leaves, and it’s an important part of chlorophyll which helps plants convert the sun’s rays into sugars, (a process called photosynthesis).
Phosphorus (P):
Particularly important in the early stages of growing, it aids in the development of healthy root systems, flowers and eventually fruits!
Potassium (K):
Helps plants handle stress such as drought, diseases and insect pests by strengthening plant cell walls! It keeps roots healthy, aids in flower and fruit production and helps with the transport of the products of photosynthesis throughout the plant.
How to Read Fertilizer Labels
If you look at a package of fertilizer, there will be 3 numbers separated by a dash that will indicate the percentage of Nitrogen (N) – Phosphorus (P) – Potassium (K) that the fertilizer contains. The numbers will always be written in that order.
For example: 20-20-20 means equal parts, 20% each of nitrogen, phosphorus and potassium.
Types of Fertilizer
Fertilizer comes in many forms and includes both organic and in-organic.
Organic Fertilizers:
Organic when it comes to fertilizer does not mean the same thing as it does when referring to ‘organic foods’. For fertilizer, it means that it’s in a less processed form, and the nutrients remain bound up in their natural forms–such as compost or manure. These offer a long term benefit to your soils and gardens as they continue to break down over time improving the overall soil quality. There is little risk of adding ‘too much’ compost to your garden beds!
In-Organic Fertilizers:
Also called synthetic fertilizers or chemical fertilizers, these are pure forms of extracted nutrients that have been added to fillers in specific ratios. This type of fertilizer offers immediate access to nutrients. These offer no long term benefits to soil, but plant improvements can happen very quickly if the problem is a nutrient deficit.
Fertilizer Formats
Fertilizer comes in many formats including water soluble, slow-release, fertilizer spikes, liquid fertilizer and compost teas. Always follow label instructions when mixing or applying your fertilizers.
Water Soluble:
These are to be mixed in with water, and that water is used to water your plants. Some water soluble products are already in liquid form, but most are granular that you would measure out. These will provide an instant flush of nutrients to your plants, but there is a risk you may burn your plants if package directions are not followed properly.
Slow-Release:
These fertilizers are applied less frequently, and as the name suggests, will release smaller amounts of nutrients into the soil as the product breaks down with the help of water, sun, heat and/or soil microbes.
Pellets or Spikes:
A bit of a set it and forget it option, this is usually larger pieces of fertilizer that are pre-measured for specific applications that you stick into the soil. They will provide extra food as the product breaks down.
How Do I Know if I Need to Fertilize?
To find out where you’re starting, it’s best to do an at home soil test to confirm if your soil is missing any vital elements. Applying fertilizer that’s not needed is a waste of your hard earned dollars, and can actually do more harm than good for your plant friend.
If you’re seeing any of these symptoms, it might be good idea to consider a nutrient deficiency as the cause:
Low Nitrogen (N):
Pale green or yellowing older leaves, undersized leaves, or short weak stems.
Low Phosphorus (P):
Red or purple tinges to leaves that are supposed to be green, or leaves with twisted or irregular shapes.
Low Potassium (K):
Lower leaves that are dead at the edges or in spots, or are wilting.
Which Fertilizer to Use for Which Plant?
Different plants are grown for different reasons – some have beautiful flowers, others produce roots we eat, some are grown for their fruit, and some for their green leaves. The fertilizer best suited for these plants will have an adjusted amount of N-P-K that will help support plant growth in the desired areas. Each plant will be a little bit different, so if you’re trying to support something specific, it’s best to research those individual plants and always follow the instructions on the package.
Indoor Plants
Being kept indoors in a container, most houseplants will benefit from additional nutrients on a regular basis throughout the growing season. Feeding can be slowed down or stopped during our cold and dark winters when most houseplants are somewhat dormant. A half-strength dose of all-purpose (20-20-20) water soluble fertilizer (shown here) once every two weeks is a good place to start, but you can also do some research on your specific plants as some might thrive with less fertilizer or more.
Annuals
Most annuals like petunias need a lot of extra nutrients to keep up those continuous blooms throughout the entire summer. You can amend your beds or planters with compost and apply an all-purpose (20-20-20) water soluble fertilizer with your watering once a week. All of the plants grown here at Heeman’s receive our own Heeman’s Blue 20-20-20 fertilizer that we have available for purchase. If you have a heavy feeder (such as petunias, calibrachoas, hibiscus or bananas) you can also add in some Heeman’s Slow Release Fertilizer (shown here).
Fruits & Veggies
Not all fruits and veggies need specific fertilizers, and at its simplest you can always use a general all-purpose fertilizer. For specialty fertilizing, those with high levels of nitrogen can be particularly useful for leafy greens, and fruiting plants (like tomatoes) often grow better with fertilizers that are rich in phosphorous and potassium.
Perennials
The majority of your perennials will do well with 1-2” of compost mulch applied in early spring. But if your soil is poor quality, you can supplement with an all-purpose granular fertilizer in the spring.
Roses
An exception to the perennial note above, roses are typically heavy feeders, and require regular nutrients every few weeks throughout the season depending on the type of rose you have. Look for fertilizers that are specifically developed for roses. Looking for more rose care info? Check out our Caring for Your Roses garden guide!
Established Trees & Shrubs
Most trees and many shrubs won’t need any additional fertilizer, depending on soil health. If required, a slow-release fertilizer in the spring that is specially formulated for trees and shrubs can be applied around the drip line.
Transplanting or Planting New Trees & Shrubs
When re-planting a tree or shrub (whether it’s new from the greenhouse or you’re switching it to a new spot in the garden), it’s a pretty traumatic experience for your plants. Avoid fertilizing right away which might add more stress, but you can consider a root boosting product like Root Rescue which helps reduce transplant shock, increases water and nutrient uptake by adding a naturally-sourced beneficial fungi called mycorrhizae that benefits the plant for their entire life!
Grass
Grass is grown exclusively for its luscious green blades, so it requires a fertilizer high in nitrogen to support that green growth. A fertilizer with the first number (nitrogen) being much higher, such as Scott’s Turf Builder at 27-0-2.
Jumping into the big world of soil health and plant nutrients can be intimidating (people can get degrees about this stuff!), but you don’t need to do all the things at once! A good place to start is by amending your soil in the spring and/or fall with a couple inches of compost as you can’t go wrong with that! Slowly increase your comfort level with additional fertilizers and specific plant needs based on what your favourites are – do you LOVE the idea of a thriving big tomato plant, or are you hoping to have the most stunning hanging baskets on the block?
You got this! And if you need some help, feel free to send us a message on social media, or better yet, stop by to speak with one of our helpful Daymakers.
