Eltham and Avery Hill Gardens Society
Eltham and Avery Hill Gardens Society

The role of N P K fertilisers in the garden

Every commercially-sold fertiliser (except for those classed as "organic"), has to carry a declaration about the amount of the nutrient elements it contains:- nitrogen (N); phosphorus (P); and potassium (K).

These are seen as providing the following benefits:

N:- helps plants to grow quickly, and also increases the production of seed and fruit, while bettering the quality of leaf crops.

P:-  plays a vital role in transforming energy from the Sun into chemical energy (photosynthesis), and encourages the growth of roots.

K:- assists in the process of photosynthesis, fruit quality, building of proteins and reduces the risk of disease.

There may well be other micronutrients present, in addition to these, the  three major elements.

Because of the way that the three major elements are described in analysis,  the "balanced" fertiliser known universally as Growmore or National Growmore with NPK values shown as 7-7-7 is not completely balanced, but in fact has more N in it than either P or K.
This can be observed when a declaration on a pack also has the declaration for sales in the Republic of Ireland (RoI).

As already noted above, fertilisers sold as "natural" or "organic" are not required to carry any declaration about the active matter content, so selection for perceived specific needs can be a problem.  
The Royal Horticultural Society writes that pelleted chicken manure, one of the most commonly available non-chemical fertilisers, has a typical average analysis of NPK 4-2-1, but is usually extremely variable

Common Fertilisers

All the fertilisers detailed below are available from the Pippenhall allotment shop on a Sunday morning at prices significantly lower than garden centres, B&Q and Homebase. All the loose fertilisers can be bought by the pound (454 grammes). See the shop page for more details. 

General purpose fertilisers- loose

Fish, Blood & Bone contains the three major nutrients for strong and healthy plant growth. 
The nitrogen in Fish, Blood & Bone encourages strong growth and healthy rich green foliage, whilst the slow steady release of phosphate promotes vigorous root growth. The added potash promotes flower colour and improves ripening of fruit and vegetables. Apply 1 to 2 oz per square yard

NPK 5 5 6

Growmore is a general purpose fertiliser for all around the garden. It contains the three major nutrients essential for strong and healthy growth. Growmore promotes heavy crops of fruit and vegetables, balanced vigorous plants and beautiful flowers. Ideal fertiliser for use before laying turf or sowing grass seed. Apply up to 4 oz per square yard

NPK 7 7 7 


Chicken manure pressed into compact pellets for easy handling. Rich in organic matter and nutrients essential for healthy growth. Helps enrich the soil and maintain the soils delicate balance. Use from February through to end of October at the recommended rate of 2 oz (50gm) of pellets per square yard. For feeding all around the garden, from vegetable plots to flower beds and borders.

NPK 4  2.5  2.3 plus trace elements ( note comment above about variability of ratios)


Flower and Vegetable A high quality fertiliser for all fruit, vegetables, flowers and roses. This all-purpose powdered fertiliser is ideal for plants, roses, fruit, flowers, vegetables and new lawns. It contains the vital plant foods and trace elements essential for vigorous plant growth, abundant flowering and ripening of fruit. Apply throughout the growing season. Highly recommended.

NPK 5  7.5  10 plus magnesium and trace elements


Bonemeal  Sterilised bone meal is a slow release organic fertiliser which provides both phosphates and nitrogen, two elements essential for healthy plant growth. This slow, steady release of nutrients over a long period make Bone meal an ideal fertiliser for bulbs and herbaceous plants, shrubs, roses, fruit trees and strawberries. Apply 2 oz per square yard when planting trees, shrubs and bulbs.

NPK 3.5  20  0

Special purpose fertilisers- loose

Potato Fertiliser contains the ideal balance of Nitrogen [N], Phosphorus [P] & Potassium [K] for growing the best potatoes. It is a homogenous granule fertiliser containing all the essential nutrients to grow this popular allotment crop. Apply in the bottom of furrows when planting seed potatoes at a rate of 2 to 3 oz per yard. Highly recommended by many potato growers at Pippenhall.

NPK 6 10 10

Rose Food is a specially formulated high grade fertiliser containing a careful balance of nutrients, with potassium and magnesium for flourishing roses. Based on a traditional formula it will give you strong growth and abundant blooms.

Apply 2 oz per plant in March/April and the same again after the first flush of flowers.

NPK 5 5 10


Lawn food- spring and summer a minigrain fertilser to give a lush green sward but also aiding the development of a strong root system. Apply from mid March onwards every six to eight weeks until the end of July. Application rate of 2 to 4 oz per square yard. If no rain within 3 days of application water in.

NPK 11 5 5


Superphosphate encourages strong root growth and healthy plants. Fruit, root and seed crops will produce higher yields and ripening will be improved. Superphosphate is one of the keys to success when planting out seedlings, rooted cuttings and transplants. 

Apply: Throughout the growing season at 2 oz per square yard, hoe or fork into the top surface of the soil, and if dry, water well for maximum benefits. Superphosphate can also be used as a liquid feed during the spring and summer.

NPK 0 17 0


Sulphate of Ammonia is a rapid acting source of nitrogen which promotes above ground growth and rich green foliage. It is especially beneficial for crops such as brassicas, lettuce, spinach, rhubarb, leeks and onions. 

An early feed gives flowering plants, shrubs and fruit a rapid boost. Sulphate of Ammonia will also quickly green up a tired lawn.
Apply evenly at  2 oz per square yard, hoe or fork into the top surface of the soil, and if dry, water well for maximum benefits.

NPK 20 0 0


Sulphate of Potash is a fast acting source of potassium which plants need to flower or fruit. It also encourages drought and disease resistance. Can be used on all fruiting plants and flowers to give larger and more abundant blooms and heavier yields of fruit. Particularly useful for established fruit trees and tomatoes. Apply evenly at 4oz per established fruit tree, or 2oz per square yard.

NPK 0 0 48


Magnesium Sulphate (Epsom Salts) is used to prevent or correct yellowing of leaves between their veins. It is vital for the production of chlorophyll and a lack of it in soil or compost leads to the above symptoms which are common in tomatoes and in many potted plants. Apply evenly at 2 oz (70 grammes) per square yard or dissolve the same quantity in water and spray over the leaves of the plant.

General purpose and special purpose fertilisers- pre packaged

Doff Tomato Fertiliser-Strong liquid feed with additional magnesium and trace elements. Concentrate with integral measure and Child Resistant Closure. Suitable for tomatoes grown outdoors and under cover. 
NPK 5 5 10 with trace elements. 


Miracle Gro all purpose  A soluble plant food which gives healthy plants with more blooms. 

For stunning displays just feed every two weeks from March to September. Highly recommended
Apply using a watering can or with the Miracle-Gro Feeder attached to a hosepipe for larger areas

NPK 24 8 16 with trace elements


Phostrogen  An all purpose soluble feed for a healthy garden. Just add water to promote healthy green foliage, abundant flowers and fruit. Helps plants become more drought resistant and develop a strong healthy root system. For use on all plants indoors and out.

NPK 14 10 27 plus trace elements.


The shop also has a selection of Chempack and other specialist fertlisers available including Miracle Gro and Phostrogen lawn feed

Allotment shop 2024 season

The allotment shop at Pippenhall is open for the 2024 season on February 4th

Growing Potatoes in bags

One of our members has experimented with growing potatoes in bags over the last two years. Read about his experience and advice to other container growers here

Pippenhall Allotment blog

One of the tenants at Pippenhall has recently started a Pippenhall allotment blog. Have a look for yourself and register if you would like to contribute to this community. Click here to visit the blog

Eltham and Avery Hill Gardens Society

Pippenhall Allotments
Bexley Road

London SE9 2PE

(please do not use this address for correspondence)



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