Casual Gardener: Free feeds will make your garden grow

Use materials at hand to manufacture your own liquid fertiliser

Turn comfrey into tea
Comfrey isn't just a pretty flower - its leaves can be used to make a very effective liquid feed

Gardeners already know how amazing plants are. Some plants can complete their life-cycle in a matter of weeks, while others will grow over centuries.

All require some form of nutrition, though once again there are huge variations in the requirements of each. For instance, annual edibles like tomatoes, which grow fast and produce lots of fruit just a few months after their seed was sown, will need lots of food, whereas something like a honeysuckle or ivy will grow over decades without any need for supplements.

All plants need a combination of three particular nutrients – nitrogen, phosphorous and potassium.

Nitrogen is good for foliage growth, phosphorous helps the roots, and potassium encourages flowering and fruit development. The trio of nutrients are collectively known as NPK, as represented by their symbols in the periodic table.

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Hanging baskets require regular top-ups with quick-release fertiliser

There are three non-mineral nutrients found in the air and water. They are hydrogen (H), oxygen (O) and carbon (C).

Plants also need micronutrients, which are boron (B), chloride (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni) and zinc (Zn). The right balance of these elements is essential for strong growth and optimum yield.

All nutrients, whether macro or micronutrients are absorbed by the plant’s roots as it takes in water from the soil.

The most strategic way to feed the plants in your garden is by preparing and improving the soil. As plants grow, they will deplete the NPK in the soil, meaning it’s necessary every so often to add fertiliser of some sort. Weeds or ‘wildflowers’ tend to prosper in infertile soil. The strong tap root of a dock, dandelion or hogweed will push its way up 30cm into the ground, seeking out the necessary nutrients.

The cheapest and most straightforward way to enhance your soil’s fertility is to add your own homemade compost, which will also improve its texture. Well rotted horse manure and seaweed will perform a similar function. You can either dig these in or add them as a mulch on the surface.

Containerised plants are much hungrier and thirstier. The quality of growing medium in a pot or such like will degrade much faster, increasing the need for a feed, which under the circumstances is best delivered as liquid. Hanging baskets fall within this category, as they need regular top-ups with fast-release fertiliser.

Commercial liquid feeds are available but you’ll have much more fun making your own. If you require large quantities then think about growing comfrey to manufacture small industrial scale batches. Reputed to be the organic gardener’s best friend, comfrey leaves contain NPK in perfect proportions, enabling you to make a nutrient-rich ‘tea’ which is diluted up to 20 times before being applied.

Like nettle (for tomatoes) or seaweed (for general use) liquid feeds, the comfrey feed is made simply by steeping the leaves in a bucket of water for a few weeks. Be warned that the desired potion stinks like a rotting corpse but will have a noticeably positive effect on your plants, both indoors and out.

Be sure to feed only when the plant has already been given a good soaking and avoid over-feeding, which will result in lush, tender growth.