Garden Q+A: When Do You Fertilize Your Plants?
I received a question a few weeks ago asking, When do I fertilize my plants and do I have to at all?
The answer to this question is completely relative to your own soil and growing schedule. I know, it's not that simple yes or no answer that you were hoping for. Fertilizing is something that is still a bit tricky to me, but I think I am beginning to get the hang of it. It's only important if your soil is lacking the nutrients needed to grow a healthy and strong plant. For instance, I received a message recently where someone said that the plants in their starting trays were dying. They thought it was because they had been in the containers too long, which is part of the issue. While it could be for many reasons that the plants died (including not enough room for roots to grow, inadequate sunlight, overwatering, etc), I assumed that it might be a nutrient issue. When you use a seed starting mix to grow seeds, it comes with all of the needed nutrients in the mixture to feed your plants. Companies do this to ensure that your plants stay healthy and green until they are ready to go outside, and that's a good thing, especially if you are using organic! After several weeks of living inside of your pots, however, the plants will use up most of the nutrients in the starter soil. They may start to turn yellow, white, or whither. You'll keep watering them and wonder what could be wrong! You may have a nutrient deficiency issue. This can easily be fixed by feeding your starts fertilizer, or plant food, in small amounts and diluted.
You can find plant foods and fertilizers at most garden centers. The choice is yours to make if you pick something organic or synthetic. We garden solely organic, so I try to use things that are cheap and easy to get my hands on such as worm castings and compost. Did you know that you can fertilize with those compounds? You can use them alone or as a tea mix, though you'll be better off fertilizing seedlings if you use a tea mix (diluted compost/worm casting in water). You'll want 4 to 6 cups of worm castings/compost per every 5 gallons of water. Mix and spray as a side dressing to your plants (meaning to spray the roots, not the leaves). You can also use other compounds such as manure (horse, cow, poultry), bone meal, cottonseed, fish emulsion, kelp meal, and other naturally occurring materials. You will want to choose which type depending on which nutrients you assume your plants are lacking.
Do you need to fertilize at all? The answer depends on if you feel like your plants are having issues with getting the correct amount of nutrients they need. The reason for your plant's poor growth could be for a number of reasons including poorly draining soil, too much or too little shade, or competition with other plants might be the problem instead. The first step is to analyze what is wrong with your plants. Do they have yellowing leaves? Are they getting enough water? Are they wilting or looking in poor shape?
The best way to find out which nutrients your soil is lacking is to perform a soil test. This is something that you can do at home, but it's not recommended. It's much easier and more reliable to get your soil tested professionally, which can be done by most local universities. Iowa State University performs soil tests for around $15 depending on what you would like to get tested. We are working to get that done pretty soon, and I hope to learn a lot about our soil here on the farm!
When purchasing a fertilizer, most will showcase how much of each of the "Big Three" nutrients are inside. This is usually done in a Nitrogen, Phosphorus, and Potassium list, respectively. It's also known as NPK - if you are around gardeners, then you'll hear this acronym often! When you read the back of a package of fertilizer, it will tell you that for every, let's say, 100 pounds there is 10-20-10 of fertilizer. That means there's 10 pounds of nitrogen, 20 pounds of phosphorus, and 10 pounds of potassium. All of these nutrients are needed to grow each part of the plant. You'll want to make sure that you are using the correct type of fertilizer for the right part of your garden; for instance, do not use a lawn fertilizer on your vegetables or a tomato fertilizer on your lawn. Just follow the package directions! This is the same when it comes to application as well. A certain type of fertilizer will tell you to apply once a week, or every two weeks, or something different depending.
The best time to fertilize plants is during their stage of active growth, which is usually before they start fruiting or flowering. In my opinion, it's smart to finish up all of your fertilization methods before plants even go into the ground. You are better off spreading compost, worm castings, manure, etc onto your garden beds in the autumn season or in the early spring. You can also place a handful of worm casting into the hole before you place a transplant in there. I did this last year, and it worked really well for me! Worm casting are the best form of soil amendment and fertilizer as they do not burn plant roots. They are purest form of humus! You can read more about them here. If you are working with plants that are already established, use fertilizer as a diluted side dressing. You always want to make a water solution for side dressings. This is a great practice for vegetables like tomatoes, peppers, eggplants, and cabbages that provide a big juicy crop.
Have any more questions about when to fertilize? Leave a comment!