Worm castings are a great way to give indoor plants a gentle fertilizer and improve the soil over time. Use worm castings to improve indoor plant potting soil before planting, apply as a liquid fertilizer or sprinkle on the soil surface to gently improve the soil.
This article will explore how to use worm castings for indoor plants. There are lots of ways to use this amazing soil conditioner to improve your indoor plant growth. Check out these top 4 ways to use worm castings for indoor plants.
Top ways to use worm castings for indoor plants
Worm castings are a great way to give your indoor plants the best start and to gently feed them over months. Check out my top 4 favorite ways to use worm castings for indoor plants.
1. Mix worm castings into potting soil
The easiest way to use worm castings for indoor plants is to mix it into the potting soil. When you are planting a new indoor purchase, transplanting a cutting or upgrading your pot size, then worm castings are great.
Mix through ½ cup full of worm castings into the potting soil for a small 5 inch pot. A good guide is to aim for a maximum of 25% of the mix to be made up of worm castings.
Put the worm castings and soil in a wheelbarrow or bucket and mix it well. Worm castings will add good soil bacteria, help the soil to hold water, will gently feed the plant roots without burning them and keep the soil moisture more consistent.
2. Apply worm castings as a top dressing
The easiest way to apply worm castings to established potted plants is to sprinkle it on as a top dressing. Take your indoor plant outside and remove any mulch on the surface. Sprinkle your worm castings with gloved hands over the surface of the pot. You only need a small handful to feed the plant.
Worm castings contain small amounts of a wide range of nutrients including calcium, phosphorus, nitrogen, magnesium and iron depending on what the worms have been feeding on. They break down the organic matter to release the nutrients in a way that make it easy for the plants to absorb.
Sprinkling small amount of worm castings on the surface will mean that the nutrients and organic matter are washed down to the plant roots to gently feed them.
I always apply an indoor plant food as well as worm castings are usually not enough to keep indoor plants fed throughout the year. Add a slow release indoor plant food in spring and fall to give your indoor plant all the nutrients they need.
For more on fertilizing with worm castings, check out my previous article here: Are worm castings a complete fertilizer? | Solved!
3. Apply worm castings as a gentle liquid fertilizer
Another great way to use worm castings for indoor plants is to use it as a mild liquid fertilizer and root tonic. Simply place a cup full of worm castings inside old pantyhose. Place this in a bucket of water and gently mix it around. The nutrients will flow out of the stocking into the water. You can then water your indoor plant with the mix.
You can also mix the worm castings straight into the water without the stocking. This will add larger particles of organic matter which are also great for your plants. The trick is to water your plants straight from the bucket and avoid using a watering can. The larger particles can block the holes of your watering can before the water comes out.
4. Apply worm castings as a leaf spray
Another way to apply worm castings is as a leaf spray add worm castings to a bucket of water by allowing it to filter through a stocking. Then add the water to a spray bottle and gently apply it to the leaves.
Take care when doing this if you live in a humid area as the extra water on the leaves can cause fungal growth. Apply the spray in the morning and take the plant outside to avoid getting worm casting water all over your house. Remember to bring your indoor plant back inside straight away so it doesn’t get sunburnt.
Do worm castings smell?
Worm castings do not smell so they are perfect for indoor plants. As long as the organic matter has been completely broken down the worm casting will have no smell at all or have a sweet, mild earthy smell. They are great for improving potting soil, top dressing or as a gentle liquid root tonic.
Are worm castings a complete fertilizer for indoor plants?
Worm castings are not a complete fertilizer for indoor plants. They contain only small amounts of a range of nutrients so will not provide enough to keep your indoor plants happy over the long term. Always feed your indoor plants with a good quality slow release fertilizer twice per year. This will give them the nutrients they need for around 6 months.
Indoor plants rely on you and the soil they are growing in for their nutrients. Most potting soil will only contain enough nutrients to feed the plant for the first 3 months, after that it is up to you to regularly feed your plants.
How to Use Worm Castings for Indoor Plants | Summary
Worm castings can be used for indoor plants as a gentle fertilizer and soil conditioner. Mix them into regular potting soil when transplanting your indoor plants, top dress with a sprinkling of worm castings or make your own liquid soil conditioner.
Worm castings will not burn the roots of your indoor plants because it does not contain a large amount of any nutrient.