If you dislike using man-made chemicals to stimulate plant growth, liquid fertilizer produced from garden weeds or other freely available plant material can prove to be an excellent alternative.
Many plants, such as nettles and horsetail, are commonly seen as useless weeds, cluttering gardens and fields. However, they can be put to very good use by gardeners who appreciate what they have to offer.
When these plants have been transformed by simple methods into liquid fertilizer, they can make an excellent source of nourishment for garden plants.
Liquid fertilizer provides extra goodness which is extracted when leaves and stalks ferment. Plants treated with liquid fertilizer have their resistance to disease increased, helping them to thrive.
Liquid fertilizer is easy to produce
Liquid fertilizer made from nettles, horsetail and comfrey has proved to be very effective. The fertilizer also has the advantage of being very easy and cheap to make. All you need is a wooden or plastic container (ceramic pots are also fine) and some of the plants already mentioned.
Fill the container to the halfway mark with plants. Then fill it up to the top with water and cover with chicken wire or a similar material. This keeps the plants under the surface of the water. The flow of air must not be impeded. Give the mixture a stir at least once a day. This mixes oxygen into the liquid, which is essential to the survival of the bacteria breaking down the plants. Within a few days, the bubbling liquid turns dark and starts to smell foul. This signals that fermentation is in full swing.
After one or two weeks, when the mixture has stopped bubbling, it is time to sieve the liquid.
Relieving the smell
The length of the fermentation process mainly depends on the temperature. The warmer it is, the quicker the process will be. To minimize the unpleasant smell, you could add a handful of bone meal or a few drops of valerian at the beginning of the process. Adding thyme or rosemary sometimes helps, and these herbs may also make the liquid fertilizer even more effective.
Lots of nourishment
The liquid fertilizer cannot be used immediately after fermentation. It is concentrated and contains large amounts of nitrogen and potash. So that it does not burn sensitive plants, the fertilizer must be diluted in water to between 1:5 and 1:10. If it is to be used for very sensitive plants, you should dilute it up to 1:20. When ready, you can apply the fertilizer using either a watering can or sprayer.
Nettle or seaweed
The stinging nettle is an ideal plant to use for feeding. You can use the stalks and leaves from the ordinary stinging nettle, Urtica dioica, or those from the annual, Urtica urens. For the best effect, harvest nettles before they flower.
Seaweed is an excellent source of free nutrients. Spread it out and hose it down with fresh water to remove salt and sand. Then make the fertilizer as you would with nettles.
Seaweed extract is a good general fertilizer and is relatively high in potash. This makes it very suitable for flowers, potatoes and fruit, including tomatoes. As seaweed can be found at any time of the year, it
makes an excellent winter and spring feed.
Horsetail
Horsetail, Equisetum arvense, is also a very suitable ingredient for making liquid fertilizer.
A mixture of nettles and horsetail combines to make a very useful preparation. For horsetail extract, steep 1kg of fresh dried plants in 10 litres of water. This should be allowed to stand for one day.
This mixture is high in nitrogen and particularly useful for brassicas and lettuce and as a spring dressing for lawns.
A 'magic' plant
Comfrey is a plant with many uses. It is a wellknown traditional ingredient in herbal remedies for people, but can also be used to fertilize plants.
Both common comfrey, Symphytum officinale, and rough comfrey, Symphytum asperum, are suitable ingredients for a liquid fertilizer with an action similar to that of nettle extract. You can also mix the two plants, as they complement each other.
Comfrey is very easy to grow from root cuttings, or by dividing the roots in spring. You can also grow it from seed. Comfrey thrives in most places where there is enough moisture.
The plants can be dried for use during times when you cannot obtain fresh ingredients. Use 100-200g of dried plants to each 10 litres of water.
However, it is always preferable to use fresh comfrey, as it contains a higher concentration of the active ingredients which are of most benefit to plants.