Houseplants brighten your home, bringing the outside in and adding an aspect of nature to your interior. They can be difficult to look after however, as it is tricky to tell whether they need more water, food, sunlight or a change in temperature. Fertilizer can help your houseplants flourish however it can be difficult to know when to apply them and how often. To help, we have done the research for you – so take a look at our guide on how and when to fertilize your indoor plants.

Types of houseplant fertilizer

There are many different types of fertilizer that can be used on houseplants, each made from their own ingredients, with their own advantages and disadvantages. There is no one type that is better than the others, so it is important to make your own decision on which you would like to use in your home. Once you have decided on the type of fertilizer, you can then look at how often to apply it.

Liquid indoor plant fertilizer

Liquid fertilizer is one of the most common types, with most brands being made from ingredients derived from plants and animals with added minerals. Some brands can be organic and act as great growth enhancers. Liquid fertilizers are less likely to cause fertilizer burn on the leaves of your houseplant and contain the vital vitamins, micronutrients, amino acids and plant hormones that will improve the health of your houseplants. Common ingredients include fish emulsion, compost tea, liquid kelp, worm tea, liquid bone meal, plant extracts, rock phosphate and humic acids.

Granular houseplant fertilizers

Granular Fertilizer is a solid version of fertilizer than comes in two different formulas – spikes or pellets. The pellets can simply be sprinkled on top of the soil that the plant is in, while compressed fertilizer spikes are pushed downwards into the soil to get closer to the roots of the plant. Like liquid fertilizers, the best brands are made from natural ingredients such as bone meal, blood meal, worm castings, limestone, minerals and other animal or plant-based ingredients. There are synthetic houseplant fertilizers however, these do not work as well as those derived from natural ingredients. If you are purchasing granular houseplant fertilizer and are not sure which type it is, simply look at the ingredients. The ingredients should be listed if it is a natural fertilizer, but if there are no ingredients, the chances are that it is synthetic.

Slow-release indoor plant fertilizer

There are some fertilizers that are specially developed to slow-release. Made from synthetic nutrients, these time-release fertilizers are liquid fertilizer surrounded by a special coating. This coating allows the fertilizer to be released in smaller doses over a longer period of time as the coating breaks down. The advantage of this type of fertilizer is that you do not need to apply it as frequently, making it perfect if you are on a busy schedule. However, the fertilizer dose may not be constant and is dependant on a number of factors such as soil moisture and temperature.

When to fertilize your houseplants

While there is no exact guidelines to fertilizing all houseplants, there are some basic steps to follow that will benefit most kinds – with the guidelines changing each season.

When to fertilize your indoor plants in Spring

After the last of the spring frost has cleared, begin fertilizing your houseplants around 8 weeks before this – usually this is around mid-March when the days are longer, and the plants begin to move to their active growth stage. As fertilizer can be strong, it is important to only use half-doses for the first few applications to help the plant get used to the chemicals being used. For granular products use half the recommended dose, and for liquid products, dilute with water. This helps prepare the plant for summer, when they are likely to grow and thrive.

When to fertilize your houseplants in Summer

The summer months are when your plant should be fertilized the most often as this is when it has optimal conditions to grow. The frequency that you should apply your fertilizer is dependent on the type of fertilizer that you are using. Liquid fertilizers that are absorbed more quickly should be applied most frequently approximately once every two weeks. Granular products should be added to plants once a month while specially designed slow-release products only need one application every three months.

When to fertilize your indoor plants in Autumn

At this stage of the year, the rate at which you apply your fertilizer should begin to taper off. From around the start of September halve the amount of fertilizer than you are using and increase the amount of time between applications. This will prepare the plant for no fertilizing during the winter.

When to fertilize your houseplants in Winter

During the winter months in most regions’ plants are not actively growing due to the cooler weather and adverse conditions. Adding fertilizer at this stage can actually damage your plants, burning their leaves so avoid at all costs unless you have properly researched your particular indoor plant.

Exceptions to the above guidelines

There are however some exceptions to these general guidelines on when and how to fertilize your indoor plants. Firstly, if you live in a climate that does not have frost in the winter, you will need to continue to fertilize your plants throughout the winter months as they will still be growing. The only difference will be that if there is less sunlight and therefore you should fertilize at around half the strength and frequency as a result of this.

There are some plants that should not be fertilized as regularly. Durable plants like cacti and succulents do not respond well to high amounts of fertilizer. These plants should only be fertilized every 6 weeks, if at all so be sure to properly research your particular indoor plants and only use this article as a general guide.

My conclusion on how and when to fertilize your houseplants

The most important thing when it comes to fertilizer is consistent application when your houseplants are in their active growth stage. Applying the fertilizer on a schedule during this period can lead to happy, healthy and growing houseplants.