Water deprived plants grow more slowly. The leaves are small and the stems spindly. The plant almost looks like it's drooping. Providing the amount of water a plant needs, not too much, and not too little, results in a healthy plant that grows quickly. Several other liquids give plants a boost resulting in lush healthy green leaves and lots of flowers and fruits. These liquids contain nitrogen, potassium, phosphorous and other nutrients that plants need to grow.
Soils contain many of the nutrients needed by plants for healthy growth. Adding additional nutrients by applying a liquid fertilizer speeds up the growth because all the required nutrients are available. Liquid fertilizers come in powdered and granular form that is mixed in with water or as ready-to-use liquids.
Smelly, but effective, manure tea is manure mixed with water and let to ripen. Well-rotted steer manure or bird manure from poultry works well. Well-rotted means it has set for 60 days before using according to the USA Gardener website. Manure from carnivorous animals, and that includes people, should not be used because of the possibility of disease. Mix one gallon of manure with 4 gallons of water. Stir well and let sit for a week. Pour around the plant but not on the leaves. You may want to strain it before using.
There is some evidence that carbonated water helps plants grow because the bubbles are carbon dioxide, a substance plants needs. Some soda water or seltzer also contains salt, which is not good for plants, so check the labels.
Dilute the commercially prepared fish emulsion per label instructions and water plants. Fish emulsion is rich in nitrogen and other nutrients. The smell goes away in a day or two but is quite noticeable immediately after application.
Green Plant Tea
Not the green tea you brew and drink but a liquid made from alfalfa and other plants. Rabbit food is compressed alfalfa. Toss in a handful of alfalfa pellets into a gallon of water, let it steep and then use the liquid to water the plants. Steep parsley, comfrey, nettle, dandelion leaves in water for a few days and use it to water plants.