Your guide to plant feeds

Nurture your soil and learn the conditions your crops love – you’ll enjoy healthy harvests and happy plants year after year.

Even if you’ve prepared your soil perfectly for sowing or planting out your fruit and veg, a little bad luck could be all it takes to leave you with fragile-looking plants. Nature is a fickle creature, and stresses caused by disease, pest attack or unseasonal weather can all take their toll. Limp plants might simply need a little boost, or heavy rain may have washed away some of the slow-releasing nutrients you’d taken so much care to build up months, or perhaps even years, beforehand. Whatever the reason, you’ll probably need to resort to a quick fix.
Thankfully, you don’t have to abandon green principles by relying on chemical fertilisers. Whether you’re looking for a general feed that will top up levels across the board, or something more specific, there are plenty of organic options available to growers.

Pick-me-up plant feeds

You shouldn’t need to add compost or fertilisers to most fruits more than once every two or three years, with just a few exceptions – notably strawberries. Mulches are important though, and should be laid in late spring.
Vegetables will need a good deal more attention. But don’t just rush out to your nearest nursery to pick up the first fertiliser you can get your hands on – you need to choose the right feed for the job. In the first instance, that’s likely to mean avoiding inorganic options which will discourage vital microbial life from inhabiting your plot. They also won’t carry the same subsidiary benefits of containing additional secondary and trace elements that organic versions do.
Crops grown in pots will nearly always need more than those in the ground because they only have what you give them – once they have exhausted the nutrients in the compost around them, that’s it.
Most fertilisers are used during the growing season in the spring or the summer. As your crops edge towards fruiting and ripening, you should avoid slow-releasing fertilisers like ‘solid’ granules and pellets, some general-purpose products, as well as feeds such as hoof and horn (soya-based alternatives are available for veggies). These are intended for preparing the soil before sowing, as an accompaniment to invaluable organic matter such as compost, manure or leafmould. They’re therefore not ideal for hasty remedies.
So, if you’re hoping to perk up frail-looking crops at this time of year, what should you be looking for in an organic fertiliser? A glance at the packaging should help point you in the right direction. You’ll find three numbers telling you the percentage by weight of the main nutrients in a given feed – ‘N’ refers to nitrogen, ‘P’ to phosphorous and ‘K’ to potassium (also known as ‘potash’). Some products will contain all of these, while others are more targeted. All are mixed with other materials to add bulk and balance.

Crop favourites

Nitrogen-hungry plants include rhubarb, onions, sweetcorn, and lettuces. Root crops and tubers, such as carrots and parsnips, crave phosphorous – but you might treat beetroot more like a leafy veg and give it some nitrogen, too. A healthy supply of potassium, meanwhile, is particularly important for tomatoes, peppers, beans, soft berries, apples and other fruits.
Some plants, like peas, are naturally light feeders and are therefore unlikely to require a helping hand. The secondary nutrients – magnesium, calcium and sulphur – should already exist in adequate quantities in a well-prepared soil. Most fertilisers will include some of these, too, along with a few much-needed trace elements.
All of these pieces of the puzzle are vital to your fruit and veg. If one is missing or in short supply, they simply won’t grow – but different plants require different ratios at varying stages of growth. Initially, you should establish healthy levels of each nutrient, and that’s why we all spend hours digging in organic matter before sowing. If you do find your basic growing medium wanting, regularly applying a general-purpose product should help, but you’ll need to address this problem on a more fundamental level before the next season.
Don’t be afraid to add ‘incomplete’ fertilisers (those which contain only one or two of the primaries) if you notice a particular deficiency, especially among established plants.

Spotting the signs of deficiency

Nitrogen is vital for lush, healthy growth. Signs of a deficiency include stunted growth and old leaves appearing small and yellowish. Most general-purpose fertilisers contain high levels of this nutrient, but few are suitable as remedial feeds. Regular applications in the mid to late season will foster heavy shoot and leaf formation when the focus of most plants should instead be on fruiting.
Of course, there are exceptions – leafy brassicas like greedy summer cauliflowers may enjoy a serving of chicken manure pellets about halfway through their growing season.
Phosphorous is especially precious during the germination stages as it encourages strong root establishment and is also needed during flowering. Plants showing a deficiency will share many symptoms with those short of nitrogen, but poor growth will instead be accompanied by old leaves turning bluish-green rather than yellow and, ultimately, small fruits.
Your veg needs potassium primarily to stimulate flowering and fruiting, though it’s also important for hardening off growth and improving disease-resistance and water intake. A deficiency is most likely to occur in soils with low clay content. You’ll typically see brown scorching and curling of leaf tips, accompanied by yellowing of veins.
Home-made comfrey (which can be harvested from mid-spring onwards) should help. Wilt the leaves for a couple of days and use as a mulch for potatoes. Alternatively, rot them in rainwater for four to five weeks and collect the black concentrate, then dilute with at least 15 parts water to form fast-acting comfrey liquid. Tomato feeds and seaweed-based products are other great organic sources of potash.

Applying feeds

Generally, you should follow the manufacturer’s instructions with regards to concentration and method of application. But err on the side of caution, especially when adding nitrogen-rich examples, as being too liberal with these could promote unruly leafy growth vulnerable to disease.
The labelling of some products may suggest regular use – perhaps weekly or monthly applications. But if you prepared the ground well originally, then a simple boost at the first signs of weakness or poor fruiting could be all you need.

________________________________________
FEED ORGANICALLY
It is worth keeping these organic fertilisers on hand to ensure you can help out any malnourished plants and enjoy a bumper crop during the summer months.
• Blood meal contains plenty of nitrogen but, as its name suggests, is a by-product of animal processing and not ideal for vegetarians. Use it sparingly – apply no more than 120g per 1m² as a top dressing during the growing season. It’s fantastic for promoting green, leafy growth, but can damage delicate roots if overused. Chicken manure is a popular alternative, and it is a fantastic excuse to keep your own chooks! Bear in mind, too, that there are some concerns about the use of such products on the veg patch. If you’re worried that ingredients such as blood, meat or bone from farmyard creatures might harbour traces of diseases such as BSE or salmonella, then you can opt for sterilised types.
• Bone meal and its fish-borne cousin aren’t for the squeamish, but they’re among the few organic options for a vigorous dose of root-strengthening phosphorous. An additional benefit of the former is its high lime content, which helps reduce soil acidity. Apply as a side or top dressing. Finer grades are faster acting.
• Comfrey can be grown on your plot and used in a variety of ways – either to top up the compost heap, as a mulch, or in liquid form for a speedy supply of fruit-swelling potassium.
• Epsom salt, a source of magnesium, is principally used to feed tomatoes. As with most fertilisers, it’s best used sparingly – fortnightly should be sufficient. Sprinkle one tablespoon per foot of height around the base of each plant to treat visible deficiencies such as the yellowing of leaves during the growing season.
• General-purpose feed is available in liquid or slower-acting soluble versions, and great for use on leafy crops, as it is usually higher in nitrogen than the other primary nutrients.
• Seaweed or kelp meal is packed full of potash. Don’t pick up your own from the beach, though – the effects of pollution have made this a risky business. Liquid seaweed also contains plenty of potassium, as well as nitrogen, phosphates and all the necessary trace elements. This makes it fantastic for a quick pick-me-up for plants, either applied to the soil as a diluted solution, or as a foliar spray.
• Tomato feed offers a good source of potassium and magnesium for pot-grown fruits, and organic versions are widely available. Remember, though, that excess potash can stunt growth and coarsen leaves, so it’s important to keep contact with brassicas and the like to a minimum.