The 7 Types of Composts for the Container Gardener (Getting the Choice Right)

In this article, the 7 types of composts for the container gardener will be discussed. As you can imagine it is quite confusing to know what compost to use in your container garden. You need to match the compost to the needs of the plant in question, and this means knowing about the growing conditions and habit of the plant is normally found in and try to replicate this in the garden.

Commercial composts that you find is different from the compost you make at home, as the home compost is not consistent enough or have the right nutritional balance. Homemade compost is more of a supplement to existing growing media and is not really suitable for growing in by itself.

Commercial composts are therefore made to be more homogeneous and nutrient-rich, as it is made in large quantities. This is made up of green waste collected from councils and other businesses and turned into compost often found in the bags you buy.

HOW IS COMMERCIAL COMPOST MADE?

Making commercial compost is an industrial process where initially the garden waste is passed through an industrial-sized shredder. The shredded material is then stocked into long piles that are 2.5m high known as windrows, where they start to heat up and quickly decompose.

These windrows are then turned over a number of times by JCBs to bring the outside material to the inside and to make sure the process is uniformly carried out. The heat generated effectively sterilizes the compost, killing weed seeds and disease material and fungal spores.

The composting process can take months but the heat does really speed up the process. Once the process is finished the compost is fed through a giant sieve designed to remove large pieces, which are then passed through the shredder again. The difference is that most manufacturers have different specifications, with some not allowing material more than 40mm in size to be in their compost, whilst others insist that a finer product is made consisting of below 20mm sized material. Finer sieves are used to produce a finer grade of compost whilst coarser sieves produce a less refined product.

The manufacturers will then use this composted material and mix it with peat (not much in favour nowadays) or peat substitute. They then add fertilizer to give it more nutrition value and lime is added to balance the pH. The exact mix is top secret and will vary from manufacturer to manufacturer.

MAKE SURE YOU GET THE RIGHT COMPOST

With compost, it is best not to skimp on quality as the pricier ones tend to be of better quality. Open a cheap compost bag and examine the contents you will be amazed at what you can find. You can find everything from stones, large wooden pieces, broken glass, and plastics. A good quality compost should not have any lumps in it and be pleasant enough to use (Some will say it should look good enough to eat).

There are a lot of composts out there and getting the right one is such a mind field, hence why this article was written. The best advice I can give is to buy a bag of those that I recommend and try it for a whole garden season. Do not expect immediate result but to be fair, give one growing season before passing judgement.

WHAT ARE THE COMPOSTS YOU CAN BUY?

The compost that you can buy is:

• Multipurpose compost

• Ericaceous compost

• Houseplant compost

• Citrus compost

• Cacti and Bonsai compost

• Seed and cutting compost

• Orchid compost

Other composts do exist but will not be touched upon here.

Remember each compost has been designed for specific plant requirements, so it is not good to mix them up. For example, it is not good to use multipurpose compost for houseplants or use multipurpose compost for lime hating plants. It will not simply work.

Each compost has been specially designed for plants so that they will thrive in them. Saying this, you can still germinate seeds in multipurpose compost, so all is not lost.

For most outdoor containers you will find that multipurpose compost will be sufficient. This is why throughout my article I always tell you what kind of compost to use, as I do not want you to kill your plants. What follows are the products that I recommend for each category of compost:

MULTIPURPOSE COMPOST

Name of Product: Professional Compost Bag 80L.

The Best Place to Buy: www.amazon.co.uk

Product Dimensions: 80 x 41 x 20cm

Shipping weight: 15kg

This is a bespoke professional-grade multipurpose compost made by one of Europe’s leading compost manufacturer. It consists of 20% composted wood fibres, which helps to retain air around the roots. It also consists of 3 blends of different grade of peat to balance water retention and drainage. To this, lime has been added to balance the pH to optimize the growing conditions, a six-month slow release fertilizer to give enough nutrients for one growing season and a wetting agent to make water distribution even. This product is not available in garden centres.

PROS

• You get professional results like those in the horticultural trade.

• Each compost is freshly made, so you know that the bag has not been outside for a long time, where all the nutrients will leach out.

• Uses the highest quality ingredients which has scientific proven to cause plants to grow larger root systems compared to other composts.

• Available in 80 litre bags that are directly delivered to your front door. No more lugging heavy compost bags around.

CONS

• Delivery charges will be expensive especially if you want more than one bag delivered.

• Contains peat and so can be said to not be totally environmentally friendly.

JOHN INNES COMPOST

Here in the UK, we cannot talk about compost without including information about John Innes. This can be confusing for gardeners but hopefully, this section of the article will clear things up.

John Innes was a 19th Century property and land dealer in the City of London. In 1904 on his deathbed he bequeathed his assets and fortune to the improvement of horticulture by experimental research. This created what was known then as the John Innes Institute, which is now part of the John Innes Centre, which is based in Norwich, England.

The institute developed and standardized formulas for compost based on loam, which was carried out in the 1930s. Loam is normally manufactured by stacking turfs upside down for six months to allow the grass to rot down into good compost. The added benefit is that by using loam, which has deposited of small clay particles in it, allows the absorption and release of nutrients to the plant as they require it.

Once the loam is produced it is sieved and sterilized before being used in compost mixes. The loam is mixed with peat to increase the water-retaining capacity of the compost and to lighten the mixture. Coarse sand is also introduced to help improve drainage before finally adding fertilizers and lime to add nutrients to the compost and to balance the acidity of the mixture.

WHAT DO THE NUMBERS MEAN?

There is where the familiar John Innes numbers come into play. The numbers are from 1 to 3 and can form to the exact recipe developed and laid down by the John Innes centre.

John Innes potting Compost 1 is for young seedling and generally has low nutrients, such as Evergreen Greendays John Innes No 1 Compost.

John Innes Potting Compost 2 is for houseplants and more mature plants. It contains twice the amount of nutrients than number 1.   I would recommend Westland 30 litres No 2 John Innes potting on Compost.

John Innes Potting Compost No 3 is the compost with the most nutrients and is designed for greedy, hungry plants.  I would recommend Levington John Innes no 3 25litres.

Most plants will grow well in standard multipurpose compost but to get the best performance you will need to add extra fertilizer to the compost.

Please note that all commercial compost the quality deteriorates with age and storage. They are often kept outside where they are exposed to the rain, where the small holes in the bag allow water in and the nutrients to run out. It is best to buy compost when it is from fresh stock. This means once bought it is best to store compost bags in garages, greenhouse or storage boxes to stop them from losing vitality over the growing season.

ERICACEOUS COMPOST

Name of Product: J. Arthur Bowers Ericaceous Compost, 50 litres

The Best Place to Buy: www.amazon.co.uk

Product Dimensions: Unknown

Shipping Weight: 10.8 kg

This is a compost where lime has not been added, so ideal for acid-loving plants such as rhododendrons, azaleas, camellias, heathers, pieris, blueberry and the many others highlighted in my various posts. It is a specialized ericaceous compost that has been blended to provide ideal acidic growing conditions.

It uses 20% wood fibres that reduce the amount of peat that is required and also has an added benefit of making the compost more open structured.

Included in the compost is a slow release fertilizer that will feed the plants for 10-12 weeks.

PROS

• A professional compost for acid-loving plants.

• Contains wood fibres and slow release fertilizer to get you acid-loving plants going.

• Reasonably priced for the volume offered.

• Can be used for a wide range of plants.

CONS

• Still contains peat which is not for you if you are trying to be environmentally friendly.

• Can be costly to deliver if you want more than one bag.

HOUSEPLANT COMPOST

Name of Product: Westland Houseplant potting compost 8l

The Best Place to Buy: www.amazon.co.uk

Product Dimensions: 60 x 27 x 33

Shipping Weight: 2.63kg

This is a specially blended mix for the repotting of most indoor houseplants including cacti and bottle gardens. This open structured compost allows it to be free-draining, allowing the houseplant to grow healthier, promoting greener leaves. It contains SERAMIS Clay granules that promote this open structure, allowing the water content of the mixture to be managed and controlled.

The clay granules in the compost mix allow the water to be absorbed and re-released when the plant needs it the most. This will allow the optimum water and nutrients available to the houseplant. The compost also contains perlite to promote better airflow and to increase the open structure of the compost. This would promote a healthier root system.

PROS

• Relatively cheap.

• A specialist blend to promote stronger and healthier plants.

• Water is better regulated, so allowing forgetful gardens to not need frequent watering.

• One bag is enough for one 28cm pot.

• Suitable for most houseplants including cacti apart from orchids.

CONS

• Still contains peat and will not benefit those who want an environmentally friendly product.

• Some people complain that it will not drain properly or slowly. This can be solved by adding more perlite.

• It will cost more to deliver multiple bags.

CITRUS COMPOST

Name of Product: Westland Citrus Potting Compost Mix, 8L.

The Best Place to Buy: www.amazon.co.uk

Product Dimensions: 60 x 27 x 33cm

Shipping Weight: 2 kg

This compost has been specifically designed for those who wish to grow citrus fruit plants. You need a compost that will keep the leaves green and help to promote the production of scented flowers and edible fruits. It is a blended mixture that is free-draining and contains the right balance of nutrients suitable for citrus plants. This is not the same mixture as found in houseplant compost so do not confuse the two.

The product contains SERAMIS clay particles that work by absorbing water, and then releasing it back to the plant when it needs it the most. This makes sure that the plant will get enough water and nutrients when it needs it the most.

The compost has plenty of loam to ensure moisture is retained.

PROS

• Relatively cheap

• Has all the nutrients required for a healthy citrus plant. Easy to use.

• Watering is regulated, so allowing gardeners to not water so frequently.

• Suitable for all citrus plants.

• Does not contain peat.

• One bag can fill one pot that is 28cm in size.

CONS

• Will be expensive to get multiple bags delivered.

• Only suitable for citrus plants and no other houseplants.

CACTI AND BONSAI COMPOST

Name of Product: Levington Cactus & Bonsai Compost 10L

The Best Place to Buy: www.amazon.co.uk

Product Dimensions: 49 x 25.9 x 6cm

Shipping Weight: 6kg

This is a pH-balanced cactus and bonsai compost that provide a slightly acidic environment in which these plants prefer to be grown in. It is ideal to repot your cacti, succulents, bonsai trees, alpine plants, and even African Violets in. It is also ideal for propagating your cacti and succulents. As it is slightly acidic it will contain little lime, and the mixture consists of loam, sand, peat, with added essential nutrients. The sand will make the compost more free-flowing and thus provide ideal growing conditions for cacti.

PROS

• Value for money.

• Can be used to grow your cacti, succulents, alpines, African violets, and bonsai in.

• Free-draining so will prevent the roots from getting waterlogged.

• Easy to use.

• Can fill one large pot.

CONS

• Will be expensive to use multiple bags if it is home delivered.

• Only suitable for a limited range of plants.
• Contains peat and therefore will not be environmentally friendly.

SEEDS AND CUTTING COMPOST

Name of Product: Gro-Sure Seed and Cutting Compost, 10 L.

The Best Place to Buy: www.amazon.co.uk

Product Dimensions: Unknown

Shipping Weight: 3.7kg

This is a specific compost for the sowing of seed or for the propagation of cuttings. It is a compost which has little nutrients but is fine graded to ensure that fine seeds can germinate without any problems.

The compost is the finest grade of all compost and contains fine peat. The compost particles are small ensuring the best contact with the seed or cuttings, allowing them to establish very quickly. It is the aim of seed and cutting compost to allow the roots to develop very quickly, allowing them to be transplanted to a more rich compost within 6 weeks.

As seedlings do not need many nutrients, as they are provided by the cotyledon leaves, then the seedling will need to be transplanted as soon as possible, as mentioned previously.

The compost contains a mixture of peat, vermiculite, fine wood fibres, and a wetting agent.

PROS

• Relatively cheap.

• Can be used to germinate all your seeds and cuttings. Will give better results than using multipurpose compost to germinate seeds.

• Resealable bag, so keeping the compost fresh.

• Can be used to fill a number of seed trays and pots.

• Can be used all year round.

CONS

• If you plan to grow a lot of seeds, you may need a lot of compost bags, so will be expensive to deliver.

• Contains peat and so not environmentally friendly.

• Only suitable for germinating seeds in or for rooting cuttings. Not designed for growing plants in.

ORCHID COMPOST

Name of Product: Levington Orchid Compost 10L

The Best Place to Buy: www.amazon.co.uk

Product Dimensions: 55 x 27 x 7 cm

Shipping Weight: 2.0kg

This the ideal compost for orchid plants as it is a free draining blend of bark and peat. The bark ensured that an open, draining structure is provided so that a healthy orchid can be grown. The compost is enriched with all the nutrients that an orchid will need so that a healthier plant is produced.

PROS

• Relatively cheap.

• Can be used to grow your orchids.

• Easy to use.

• Resealable bag keeping the compost fresh.

• Can be used all year round.

• Can fill one or two pots.

CONS

• As ever if you have multiple pots to fill it would require a number of bags to be ordered and therefore costly to deliver.

• Contains peat and therefore not environmentally friendly.

CONCLUSIONS

In this article, the seven types of composts for the container gardener have been discussed. You can see that no matter your container plant is or how you want to propagate your seeds in, there is a compost for you.

For most outdoor container plants multipurpose compost or ericaceous compost can be used. Ericaceous compost being used for acid-loving plants, whilst multipurpose compost used for the rest.

For indoor plants, the picture is more complex, as you need to tailor your choice to the plant growing in it. This would be houseplant compost for most, but for cacti, succulents, alpines, African Violets, Bonsai trees, Orchids, and Citrus plants, would require another kind of compost. This is why 7 compost types are required if you want a complete solution to all your container growing needs.

I have mentioned the 10 best compost that I would use to get the best from my indoor and outdoor container garden.

If you have any questions or comments that you wish to make, please do so in the usual comment box below.

Happy Container Gardening.