Plants need a balanced diet of thirteen primary nutrients for quality growth over a season. A deficiency of one or more nutrients will cause many issues, including lowered rates of photosynthesis, susceptibility to pests or diseases, and a gradual decline of health. Although there are three main elements (macronutrients), N, P & K, plants require a varied and balanced amount of each trace elements to become well-nourished. Have a look at the basic functionality of each nutrient below, and what it does within the plant!
Nitrogen (N) - Aids the establishment and greening of leaves.
Phosphorus (P) - Stimulates root development and the resistance of diseases.
Potassium (K) - Stimulates the flowering process, and can harden certain species from frosts.
Calcium (Ca) - Compliments the development of roots and encourages seed production.
Magnesium (Mg) - Aids the uptake of phosphorus and other nutrients through the roots.
Sulphur (S) - Stimulates root and nodule production.
Iron (Fe) - Mandatory for the formation of chlorophyll and protein synthesis, along with being a macronutrient for acidic soils.
Manganese (Mg) - Development of chlorophyll.
Zinc (Zn) - Better regulates the plant's hormones, including chlorophyll & auxin.
Copper (Cu) - Aids respiration.
Boron (B) - Compliments the absorption of nitrogen and cellular division.
Molybdenum (Mo) - Essential for nitrogen-fixing organisms.
Chlorine (Cl) - Aids photosynthesis.
• Most nutrients within the plant aid the development or regulation of chlorophyll, which is the 'engine' of photosynthesis. Situating a plant in a dark location with little fertilisation will significantly reduce its ability to convert light energy into sugars, thus weakening the overall health.
• Over-supplementation will have its negatives too, in the likes of root-burn, yellowing leaves and elongated growth. Fertiliser salts will begin to build-up in the soil, creating an imbalance that can lead to a depressive plant. If it's felt that you've given the plant too much 'love', soak the soil to allow the excess moisture and chemicals to drain from the roots freely.
• The compost's pH will significantly govern which nutrients are retained in the soil. A 'neutral' reading of 7 will hold the most nutrients, whereas acidic soils (below 6) will cause many of them to leach-out, except for iron, manganese and boron. Acid-loving plants, like Azalea or Rhododendrons, will require large quantities of the nutrients to function adequately. Although knowing your houseplants' pH score isn't overly critical, excessive use of tap water will slowly turn the soil too alkali (over 7), that is highly detrimental to certain species.
Most fertilisers will be based off the three macronutrients, Nitrogen (N), Phosphorus (P) and Potassium (K), but some will include all thirteen. Upon choosing the right fertiliser for your houseplant, make a note of what you want the plant to do.
Foliage or Leaves - Opt for a fertiliser high in nitrogen; an example of this would be BabyBio, with the NPK ratio being 10.6 - 4.4 - 1.7.
Flowers & Fruits - We recommend a form of tomato feed, as it'll provide a high dose of potassium. 'Tomorite' is a good example, as the NPK ratio is 4 - 3 - 8.
'Houseplant' or 'Foliage' labelled fertilisers can be used for almost all indoor plants, except Ericaceous (acid-loving) species. They'll come in many forms, with most popular being concentrated bottles or drip feeders. Out of the four leading companies, we'd recommend 'BabyBio Concentrated Plant Food' as it provides a great blend of nutrients and is readily available at all garden centres. Although you can buy a 'Ready-to-Use' (RTU) fertiliser that'll be great for easy application, it's an expensive way to supplement your plant in the long run.
● 'Foliage' Houseplants That Bloom Periodically
Plants that are predominantly grown for their foliage (like Peace Lillies) may flower from time to time. Although its regular feed will still aid this process, you may want to consider something that's higher in potassium. The obvious choice is Miracle-Gro, as they're renowned for adding higher quantities this in their products. But there are also other products that you wouldn't necessarily associate with promoting better flowers; Lorbex's Streptocarpus Food or Fito's Poinsettia Feed is usually much cheaper than their famous counterparts, so why not purchase one of these to save some money?
Tomato feed is another fantastic fertiliser to lengthen the blooming process, but be careful of over-supplementing the soil as it can lead to root burn.
Orchid growers, as it'll improve the health and vigour of the leaves, but isn't mandatory for a bloom. Our recommended product is 'BabyBio Concentrated Orchid Food' due to its popular demand and being readily-available in all garden centres.There are hundreds of brands to choose from, with all having near identical results. We'd recommend purchasing a concentrated bottle over a few drip feeders, as it'll be cheaper and will last longer in the grand scheme. Foliage Misters are also highly popular among
You have an option to choose either a Cactus & Succulent-labelled fertiliser or a generic 'Houseplant' product, as both will provide near-similar quantities of nutrients. The only difference between the two is that 'Cactus & Succulent' products will learn towards potassium (flowers), whereas 'Houseplant' products will provide more nitrogen (foliage). We'd recommend Growth Technology's Cactus Focus, as it allows for all of the nutrients in the correct proportion, with being much cheaper than other products.
N. B. - If you're going to use an RTU fertiliser, be sure to pre-water the soil beforehand to prevent root burn. The combination of dry roots and harsh chemicals may lead to stunted growth and yellowed foliage.
Although it'll be great to purchase a Bonsai-labelled product, a general 'Houseplant' fertiliser will do the job, too. We'd recommend 'BabyBio Concentrated Houseplant Food' (left on image) as it provides the correct levels of both nitrogen and phosphorus for solid foliar and root development. ukhouseplants would avoid Miracle-Gro as it'll provide an overload of potassium and not enough nitrogen for the desired green foliage.
For successful flowers and fruit, you should opt for a fertiliser high in potassium. There are many options to choose from at a standard garden centre, but we'd recommend 'Tomorite's Concentrated Tomato Food' as it favours potassium over nitrogen. If, however, you have a leftover box of 'Sulphate of Potash' at home, now is the time to use it - just follow the guidelines for application and halve the recommended dilution strength to avoid burning the roots!
Because of the high counts of iron, manganese and boron found in acidic soils and fertilisers, you must only use ericaceous-labelled food and compost. A too-alkali fertiliser will result in yellowing leaves, poor growth and a general decline in health. For this reason, we'd recommend 'Wilko's Liquid Ericaceous Plant Feed', as it's very cheap and contains the correct ratio of nutrients.
Every brand mentioned above is all synthetic fertilisers that have a very little plant or animal-based nutrition. Although it's rare to find organic products at a garden centre, more and more companies are beginning to break onto the market.
Organic fertilisers are highly beneficial for plants, as they'll add a non-chemical dose of nutritional value to the soil. Not only that, but they also have a lower risk of causing root burn, when excess fertiliser salts build-up around the roots. As mentioned above, there are only a few organic products on the market, and they all seem to favour potassium over nitrogen. This is great for flowering or fruiting specimens, like Citrus or Cyclamen, but not overly suitable for 'foliage' houseplants. For the interest of this article, we'd recommend 'Vitax Liquid Seaweed' as most seaweed products contain high levels of phosphorus for healthy root development. If you can't visit a physical shop or garden centre, have a look at 'Origins Organic Plant Food' as it'll surface around the £5 mark for 500ml online, which is relatively cheap for an organic-based product.