You have treated your lawn to some fertilizer but are wondering whether to use what is remaining for your garden plants. The thing is lawn fertilizer tends to have a different chemical composition than what you will find in normal fertilizer that you use for your plants. Often it is rich in nitrogen but a bit lean on phosphorous and potassium. The high nitrogen content in lawn fertilizer is what is responsible for the lush green color in your grass.
Nutrient composition in lawn and garden fertilizer
Whenever you go purchase fertilizer you will find numbers printed on the bag. These numbers indicate the chemical composition of the three main components – Nitrogen, phosphorous and potassium (N-P-K). It is common to see numbers like “5-10-15”. In this instance, it means you have 5% nitrogen content, 10% of Phosphorous, and 15% of potassium. The rest of the percentages are filled with other compounds in fertilizer that are beyond the scope of this article.
Why is it wrong to apply lawn fertilizer on garden plants?
While nitrogen is good for all plants too much of it promotes garden plant green growth at the expense of fruit and flower growth – which is what you desire. The lawn is pretty much comfortable consuming more nitrogen as it is responsible for its green color. Phosphorous and potassium, which are mostly used in lawn fertilizer (sometimes none existent), are responsible for root development and photosynthesis. They also contribute to strong plant stems.
A quick glance of some lawn fertilizers in the market will reveal that the chemical composition looks something like 6-4-0. This means you have 6 pounds of nitrogen for every 100 pounds in the fertilizer, 4 pounds of phosphorous and zero content for potassium. If you were to purchase this kind of fertilizer and use it in for your garden plants, you will need to supplement it with some potassium.
Can I still use lawn fertilizer for my plants?
The answer is yes, as long as the lawn fertilizer does not contain any herbicide or pesticide. Since the lawn fertilizer is rich with nitrogen the best way to apply it is to scatter it at a rate of 1/5 or 1/4 . Once done supplement this with another fertilizer that balances out the nutrients. It is also wise to check whether your plants will negatively be affected by high nitrogen doses.
Two main types of herbicides used in fertilizer are broadleaf weed killer and crabgrass control. When it comes to application on plants and trees, the crabgrass control herbicide is okay to use while the broadleaf weed killer is harmful. You also need to be extra careful how you apply these herbicides as it should not even be exposed to your trees roots.
Neutralizing soil PH
While most grass is tolerant of slightly alkaline or acidic soils, many shrubs like rhododendrons, azalea, and blueberries do well in acidic soils. If you have a couple of such shrubs it is wise to apply some iron or acidifying elements. This is because most lawn fertilizers do not have these.
When is the best time to apply fertilizer?
The rule is that a warm season lawn should have fertilizer applied throughout summer while a cool-season lawn during spring or fall. For shrubs to encourage new growth, fertilize in late summer or fall. However, try not to fertilize in the middle of summer. New growth is often hindered in the cold seasons.
What is fertilizer burn?
The term is used to describe the action of over fertilizing your plants or applying some of the fertilizer on wet foliage. The burn is as result of the salt content in fertilizer that leads to them drawing water from the plants. This leaves a yellow discoloration on the leaves or roots. Fertilizer burn is visible a day or two and in some times a couple of weeks after fertilization. To prevent it, just be zealous in using the right amount of fertilizer for your lawn. It is not true that the more fertilizer you use the better looking your lawn.
For some plants the best practice is to mix the fertilizer with compost. This reduces the risk of fertilizer burn if the plants are covered with compost to 1 to 2 inches. It is also good practice not to fertilize your lawn when the leaves are wet. Instead, wait until the weather improves them apply the fertilizer.
If you accidentally over fertilize your plants, make every effort to scoop the excess fertilizer. You can also try to flush the soil with as much water as possible so as to drain the excess fertilizer. Also, note that excess fertilizer when passed on to waterways can cause further chemical pollution.
Whether to use your excess lawn fertilizer for your plants is a question of the chemical composition of the fertilizer. If it contains a lot of nitrogen with little potassium, then you will need to supplement what is missing to your plants so that they do not fail to flower.