Yesterday I discussed what fertilizers are and understanding the numbers on the label. If you recall, fertilizers are either organic or inorganic and are labeled with the N-P-K content but some may also include the S content in the form of N-P-K-S. It is important to choose a fertilizer based on the plant's needs. If you want a nice, bushy plant with lush greenery, choose a fertilizer high in nitrogen (N) content. If you want a plant with good fruit development and a strong root system, choose a fertilizer high in phosphorous (P). If you want a plant with beautiful, showy flowers, choose a fertilizer high in potassium (K). Don't forget the importance of the other three macronutrients (calcium, magnesium and sulfur) or the micronutrients boron, chlorine, copper, iron, manganese, molybdenum and zinc.
Fertilizers are available in liquid and granular forms. You can also buy pressed fertilizer spikes that are pressed or pounded into the soil. Liquid fertilizers feed the plants upon application so need to be reapplied at regular intervals. Pressed fertilizer spikes and granular fertilizers are slow release fertilizers. Once applied they will feed the plant then slowly release fertilizer for a couple of months continuously feeding the plant each time it is watered. There are benefits to using either. Soil amendments like compost will also continuously feed the plant as they continue to break down. If you are busy or are away from home for extended periods, the slow release fertilizers will keep your plants healthy without the extra attention. If you use self-watering planters, liquid fertilizers will achieve the same goal when added to the reservoir water making your container plants very low maintenance.
The use of inorganic fertilizers can cause the depletion of micronutrients (trace minerals) in the soil. This is more of a concern for those growing in traditional garden beds. Some soil amendments (eg. mulch, compost, leaves) are great inexpensive fertilizers. Fish or manure tea is a wonderful, inexpensive organic fertilizer for container plants. Other soil amendments (eg. manure, straw) are also good but can cause problems. For example, manure can cause fertilizer burn if applied heavily and straw will introduce more weed seeds than any home gardener wants to deal with. Fertilizer burn also occurs due to over fertilizing. Leaves will brown and in some cases the plant will die.
I personally prefer to use organic fertilizers on all edible plants. I do use inorganic fertilizers on ornamental plants and houseplants grown in containers but use organic fertilizer for any ornamental grown in actual garden beds. I use organic oil amendments like compost in my container plants both indoors and outdoors. When I plant tomatoes and peppers I always add epsom salts (magnesium sulfate) to the hole then monthly thereafter and I use epsom salts for my plants in containers. I also use organic or inorganic fertilizers for all plants I grown hydroponically including clippings being rooted in water (eg. impatiens, tomatoes, pothos, ivy) with organic fertilizer used for all edible plants.
Fertilizer should be applied every two to four weeks, bi-weekly for container plants including raised beds and weekly if growing hydroponically. You can fertilize every time you water especially for container plants. In this case, you use a very dilute fertilizer solution. You can also use soil amendments that will continuously feed your container plants. Do not fertilize if using a potting mixture with a time released fertilizer or on a newly purchased plant with a time released fertilizer in the soil. A slow release fertilizer can be recognized by the appearance of small round balls that will be green, white or brown. If a plant is diseased or is infested, treat first then fertilize lightly. Fertilizing will help the plant recover. If you are using self-watering planters, add a dilute fertilizer solution to the reservoir
Never fertilize a plant in dry soil! The thirsty plant will take up too much fertilizer when watered causing damage to the roots and fertilizer burn. When applying any fertilizer with the exception of mulches, compost and leaves always water first then apply the fertilizer to prevent fertilizer burn. Don't over fertilize but in the event if you accidently over fertilize a plant in a container, flush with clear water to help remove the excess fertilizer. This will minimize the damage but you can still expect a bit of damage to the plant.
Happy Gardening!
Garden Gnome
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