In nature, plants have all their needs met when growing outside. The rain provides water, the sun provides light and the environment will provide the nutrients the plant needs. It is a continual cycle of growth and decay as well which provides those nutrients. In your home, the plants are confined to a pot with no input of any kind unless you provide it. Of course. your houseplants will not survive unless you give them enough light and water, but for a while, they can get along pretty well without fertilizing.

First of all, make sure the plants have been well-fertilized prior to you purchasing them. The seller wants the plants to look their best with a sturdy healthy appearance and full foliage. So, they arrive at your home with a supply of fertilizer already in the soil. After a few months, the nutrients in the soil have been depleted and your plant doesn’t look quite so robust. The leaves may be a lighter green or even dropping off. There isn’t as much growth and maybe no flowers. If you want your house plants to live for years, it is time to learn about plant fertilizers.

Fertilizer for houseplants comes in two basic types: organic and chemical. Organic plant fertilizer is made from plant and animal materials like seaweed, worm castings and compost. This type of fertilizer is similar to what a plant would have available if growing naturally outdoors. It is difficult to measure the exact amounts of nutrients, but it is safe to assume it is in small amounts, which is why this type of fertilizer is often called a gentle fertilizer. Organic fertilizer will also contain nutrients like sulfur, copper and iron, as well as good bacteria and fungi that are essential for the plants to grow but in even smaller amounts.

Manufactured fertilizer is made in a lab and is usually much higher levels of ingredients than organic. The advantage of this type of fertilizer is that you will know exactly what is in the fertilizer and how much of each macronutrient. These are the fertilizers that come with a series of three numbers on them like 10-10-10 or 12-6-6. Some manufactured fertilizer also includes other chemicals plants need and the label detail will also give the exact amount of these included in the fertilizer. The series of three numbers refer to nitrogen, phosphorus and potassium (potash). They are always in that order and each has its own contribution to your plants.

  • The first number refers to the amount of nitrogen in the mix. Nitrogen is the key ingredient in the manufacture of chlorophyll, which the plants use in photosynthesis. This is the process the plants use to turn light into energy. Nitrogen is also necessary for the plant to make plant proteins. Feeding your plant with nitrogen will give your plant the ability to grow and produce lots of healthy green leaves.
  • Phosphorus. Phosphorus is used by the plant to grow flowers and fruits. You want a higher second number if your plant is a flowering plant. Phosphorus is also important for developing a strong root system.
  • The third number is always the potassium level in the fertilizer. Potassium is a regulatory chemical for plants. Potassium controls the opening and closing of the stomata or pores on the plant surface. This is where oxygen and carbon dioxide are exchanged and moisture balance is maintained. With sufficient potassium, your plants will be healthy and vigorous high-quality plants.

It is important to understand the function of each ingredient so that you can choose the best mix for your plants. If you give a higher nitrogen fertilizer to a flowering plant, the nitrogen will want to stimulate leaf growth and it could lessen the number of blooms or even prevent the plant from blooming at all. But if the beauty of your houseplant is the leaf structure and the flower is unimportant, the higher nitrogen is appropriate.

Fertilizer comes in several forms. Houseplants are in greater danger of over-fertilizing than under-fertilizing. Liquid fertilizer is easy to mix. Just shake the liquid well and then add the amount into the water to dilute it. You can purchase the same fertilizer in a powder form that you mix into a small amount of water until dissolved and then add the appropriate amount into your container. Another option is time-release granules. This fertilizer is pelletized, and the pellets are scattered on the soil surface. As you water your plant, the pellets will slowly disintegrate and release a small amount of fertilizer. One application will last three to four months. Lastly, there are spikes. These are composed of fertilizer compacted into a binding ingredient to form a small spike. The spike is inserted into the ground close to the stem and it will gradually disintegrate, releasing the fertilizer over time. Spikes also last several months.

Deciding when to fertilize is based on understanding the growth cycle of your houseplants. Just as plants outdoors go into dormancy during the winter, so do houseplants. Although the temperature doesn’t drop significantly indoors during winter, the amount of light does. Growth will slow down and the plant will not need to be fed. About two months before the last frost date, start your feeding program for your houseplants. Mix the solution to half the recommended concentration. If your fertilizer says to mix two tablespoons of fertilizer to a gallon of water, cut the amount of fertilizer to one tablespoon in a gallon of water. Add enough solution to your plants so that a small amount is dripping through the holes in the bottom of the pot. Do not add fertilizer to dry soil. The soil should be damp so that when the fertilizer solution is applied it will be evenly distributed to the entire root system. Feed half strength for the first three feedings and then you can switch to the recommended concentration for the summer months of maximum growth. In the fall, reverse the process starting about eight weeks before the last frost and again stop feeding in the winter months.

Every plant has its own unique needs. Some are heavier feeders than others. Some plants need very little feeding. For the average gardener with a few plants in their home, divide your plants into blooming and non-blooming. The non-flowering plants will do well with a balanced fertilizer like when the N-P-K ratio is equal, such as 10-10-10. The flowering houseplants will benefit from an increase in phosphorus so a 10-20-10 would be better.

Remember that under-fertilizing is less harmful than over-fertilizing. Over-fertilizing can burn your plants and even kill them. Err on the side of caution. With a regular program of fertilizing, your houseplants can grow and thrive, giving you years of enjoyment and beauty.

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