The best thing you can ever do for your container plants is to give them compost tea from your vermicomposting bin. Compost tea is cheap and simple, and it will make your plants explode with growth.
The first step to making compost tea is to establish your worm bin. After a few months of feeding the bin, you will see a nice bit of black worm castings. The best way for balcony container gardeners to harvest the castings is to spread them out onto plastic grocery bags in the sun. Other methods use extra bins and buckets, and most balcony gardeners do not have the space for this extra equipment. Spread the castings out into a thin layer onto the plastic bags and set it in the sun until it dries. This way you can see if any worms are left in your pile. You will most likely end up with some worm eggs that will survive and hatch in your plant containers. Whenever you find a red worm in a container (this is common when transplanting), simply put it into the worm bin.
After the castings have dried, put about 3/4ths of a cup (it’s not necessary to measure it) of the castings into a gallon jug (like an old milk jug). When you are ready to water your plants, put water into the gallon jug and shake up the mixture. Some say that the castings should be used right away, but you will still see spectacular plant growth even if your worm castings are a month or two old. It isn’t necessary to constantly harvest the castings. About once a week, add the compost/water mixture to your container plants.
When watering your container plants with compost tea, keep an eye on your plants. Some plants do not respond well to too many nutrients and should not receive as much compost tea as others. If you notice yellow leaf tips, it means you are giving the plant too many nutrients.
Giving your plants compost tea is not an exact science. Do what’s easiest for you when harvesting and feeding the plants in your garden. See how long you can keep worm castings and still see great growth.