A complete guide to choosing the right compost

Adding compost or a soil improver helps to provide the right growing conditions, which will ensure you achieve bigger and healthier results. Find out how to choose the right compost for you.

Why do I need compost?

Some garden soils can be good for growing plants, fruits and vegetables; however they can vary considerably (even within the same garden) and very few gardeners are lucky enough to have perfect soil. Adding compost or a soil improver helps to provide the right growing conditions, which will ensure you achieve bigger and healthier results.

Choosing the right compost is essential to get the most out of your plants/fruit/vegetables, but the ingredients that make up different composts can vary dramatically. For the best results it is wise to use a ‘fit for purpose’ compost, which has been tailor-made for the job in hand.

The do’s and don’ts of compost

The do’s

  1. Do choose a specialist compost for the task in hand, this will ensure you create the optimum growing conditions.
  2. Do check out your garden soil pH balance before you get planting, and depending on the results, you may need to mix in Lime soil improver to get you started.
  3. Do use any leftover compost and dig into your existing soil around your garden as a soil improver.
  4. Do pot up your existing and new plants in fresh compost each year to minimise pests and diseases being carried over, this will also provide new nutrients that will have been used up.
  5. Always water in your plants (even if the ground is moist) to remove air pockets and ensure the roots are in contact with the soil.
  6. Do use gloves when gardening.

The dont’s

  1. Don’t sow seeds in standard compost for best results use a specialist seed compost that provides optimum root growth and contains plant food to help them develop.
  2. Don’t be put off from growing fruit and vegetables by lack of space. You can achieve healthy crops in pots, hanging baskets and grow bags even in the smallest of areas.
  3. Don’t forget that some acid loving plants such as azalea, camellia or rhododendron will require an ericaceous compost with a lower pH.
  4. Don’t assume that there are enough nutrients in your garden soil to use for potting up containers and baskets. It may contain unwanted weeds, pests and diseases and also the soil won’t hold as much water as potting compost would, so your plants may suffer.
  5. Don’t forget that decorative barks not only look great on beds and borders, but they suppress weeds and help retain valuable moisture too.
  6. Don’t forget to follow the compost label instructions

Different types of compost

Broadly speaking, there are five different types of compost:

1. Peat based compost

There are many formulations of peat based composts available to the gardener. These are made from a base of peat blended with other ingredients such as fertiliser, sand and/or grit, vermiculite or perlite, wetting agents and lime. The exact formulation will depend on the intended use of the compost.

2. Loam based compost

John Innes Composts are soil-based made from a mixture of loam, sand or grit and peat with increasing amounts of plant foods added.

3. Peat free compost

Peat free compost can be made from several different base ingredients, such as wood fibre, composted bark, coir, and green compost.

Specialist composts are then produced using one of the above as a base, to which other ingredients are added depending on what they are to be used for. These come under the following headings, which also has an explanation of what they consist of and where they are used.

4. Organic compost

Organic composts contain a mixture of materials e.g. peat, expanded wood fibres and composted bark in varying proportions. They are enriched with naturally occurring nutrients, derived from plants and animals, to feed plants for differing periods depending on the organic compost purchased, some feed for up to 3 months. In addition, composts may be certified as organic by organisations such as the Organic Farmers and Growers Association.

5. All/multi purpose compost

This is a compost that can be used in various parts of your garden, from beds and borders, to pots, containers and hanging baskets. They come in different blends of ingredients, for example, some contain varying plant foods that will feed your plants anywhere from 6 weeks, up to 6 months – others will limit the amount of watering you need to do, by absorbing water then storing and releasing it as and when the plant requires. You can get peat free and added John Innes.

  • Miracle-Gro All Purpose Enriched Compost: Enriched with Miracle-Gro Plant Food, this premium low peat compost is guaranteed to grow plants twice as big (versus ordinary garden soil). It also contains Smart Release Feed granules that allows season long feed.
  • Miracle-Gro Peat Free All Purpose Enriched Compost: Produced using a unique and revolutionary Fibresmart Technology - the hollow wood fibres are 100% natural and peat free. They ensure the optimum balance of air and water for strong roots to grow healthy and beautiful plants. Also includes smart release granules giving the plant a season long feed.
  • Levington Multi Purpose Compost: Its superior texture helps plants all around the garden, develop stronger roots and healthy growth. Has a low peat formula and absorbs 25% more water than ordinary multi-purpose compost.
  • Levington Multi Purpose Compost with added John Innes: Based on Levington® Multi Purpose Compost, with added John Innes (sterilised loam, peat and grit). Used by many professional and traditional gardeners. Provides extra weight in pots for top-heavy plants.

Top tips

  • Most plants you buy from garden centres are already planted in suitable compost, so you need to try and match these conditions when you plant, to encourage the roots to grow out and into the ground. This means enriching the planting hole with a good all purpose compost. Make sure you tease out the roots when planting into the ground.
  • Autumn is the best time to plant out all permanent bed and border plants, giving the roots time to establish before winter sets in.
  • Make sure the container has good drainage holes and add a layer of stones, gravel or crocks (broken plant pots) to provide a good drainage layer. Line terracotta pots with plastic to reduce water loss but make sure there is still a drainage hole in the base.
  • Acid loving plants must be planted in a specialist ericaceous compost, such as rhododendrons, azaleas and camellias.
  • You’ll need to give your plants an additional boost once any plant food in your compost has been used. For fantastic results, make sure you feed them regularly with products such as Miracle-Gro All Purpose Plant Food.
  • If you don’t use all of the compost bag, make sure you store it somewhere dry and roll the top down to keep it moist.
  • Compost should be used within a year, as after this time the nutrients and any added feed will lose performance.

Barks

Bark can provide a clean visual background that makes plants and flowers stand out. However, applying a layer of organic material, such as bark (known as mulching), does more than make your garden look attractive, it also helps to retain soil moisture, suppress weed growth and will gradually improve the structure of your soil.

You can get other various types of mulch, such as pebbles, sea shells, slate, cocoa shells and coloured wood chips.

Top tips

  • The best time to lay down a layer of bark or mulch is when the soil is thoroughly soaked through, warm and free from weeds. Generally this is in early autumn or early spring.
  • You should put down a layer that is at least 5cm thick, as this will help prevent water evaporation.
  • There are various bark and mulch products available, so you can choose the one you prefer the look of. They come in all different colours and sizes, so take your pick.

Bulb fibre

This compost has a more open texture which helps with root growth and has little nutrient content, as bulbs themselves don’t really need them to develop until flowering stage. This compost normally has ingredients such as charcoal or oyster shells in it, which keeps the compost fresh.

Top tips

  • Put a thin layer of gravel on the top of the pot, this will help with moisture retention and stop weeds from growing.

Grow planters/sacs

These are great if you are limited on growing areas in your garden, as they take up very little space and can be placed just about anywhere. You can grow all sorts of wonderful fruit, veg and herbs, from salad leaves, Tomatoes, Carrots, Potatoes, Onions, Strawberries and Cranberries. Most will have a plant food mixed in, that will feed for up to 8 weeks, after this time you would then need to feed regularly, you can also get peat free and special water absorption ingredients mixed in.

  • Levington Tomorite® Giant Planter with Seaweed: A bigger bag for better growth. Designed to absorb and store more water, meaning you don’t have to water it so often. Enriched with both Tomorite® Plant Food and Seaweed, you can expect a delicious top quality crop of full flavoured tomatoes.
  • Levington Original Gro-Bag: Perfect for vegetable crops. Ideal for growing tasty tomatoes, peppers, aubergines, cucumbers, green beans and melons.

Top tips

  • If you’re planning to plant directly into your garden soil, add a soil improver to enhance growing conditions.
  • Don’t let a lack of outside space put you off growing your own. You can produce an abundance of crops in small pots, containers and window boxes, which will fit nicely onto the smallest of outside spaces.
  • If you have children or grandchildren – get them involved! They can help you sow the seeds, care for them, harvest, cook and enjoy eating the delights of their labors.

Potting compost

This compost is best for starting plants off, either seedlings that you have grown and are at the next stage or young plants you have brought. Most will have the added extras that your young plants need, to help them develop into strong healthy mature plants.

  • Levington Seed & Cutting Compost: For sowing seeds, striking cuttings, delicate seedlings. Unique balance of nutrients for stronger, healthier plants. Specially formulated with high-phosphate content for optimum root growth.
  • Miracle-Gro Moisture Control Enriched Compost Pots & Baskets: Perfect for hanging baskets, patio pots and houseplants. Exclusive Aquacoir formula stores and releases water when plants need it. Absorbs twice as much water as ordinary multi purpose compost. Feeds for up to 6 months.

Top tips

  • Make sure you only pot up one size at a time
  • To prevent roots from growing out the bottom of your pots, raise them 1-2cm off the bench, this will also allow air to pass under the pot

Seeds and young plants

Young seedlings are very sensitive to their environment and need different nutrients and care to more mature plants. Normal potting composts are too rich in most of the nutrients, and have a texture that is too coarse for fine seedling roots to penetrate. Specialist seedling compost have generally lower nutrient levels but higher phosphate, which helps to develop a strong root structure. It also has a finer texture to create the perfect surroundings for the young plants to flourish.

  • Levington John Innes Seed Compost: Ideal for maximum root growth of seedlings and root cuttings. Contains a traditional mixture of loam, peat and sand. The use of sand increases drainage in the compost which helps the development of seedlings. Produced with the specially balanced nutrient levels.
  • Levington Seed & Cutting Compost: Specially formulated with high-phosphate content for optimum root growth. Ideal for anything small and sensitive such as seeds, striking cuttings, delicate seedlings and all sensitive young plants.
  • Levington John Innes No.1: With a specially balanced nutrient mix ideally matched to the needs of developing seedlings, young plants, and newly rooted cuttings, this compost features a traditional mix of loam, peat and grit.

Top tips

  • Many plants can be grown from seed but their requirements are all different. Make sure you check the care instructions before planting and follow them closely.
  • Avoid feeding your seedlings until they are established to avoid damaging them or causing a surge in growth too soon.
  • When buying seeds, look out for varieties marked ‘F1 Hybrid’. These have been specially bred to produce more vigorous growth and beautiful blooms.

Soil conditioner

These are used to improve aeration and drainage in heavy clay soils and adds body to light sandy soil, which aids in retaining moisture and nutrients. It also boosts the soils fertility by adding some nutrients, that will encourage healthy foliage, flowers and root growth.

Top tips

  • It’s unlikely that you will be lucky enough to have naturally good quality soil, dig through a product such as Levington Organic Blend Soil Conditioner to greatly improve your results.
  • Don’t get rid of any worms that are in the soil when digging in, as worms help with aeration and drainage.

Specialist

Covers a multitude of specialist plants from Roses, Ericaceous, Cactus and Bonsai’s, all of which have specific requirements from the soil they are grown in. Each dedicated compost will contain what that specific plant needs, and if you try and grow these in the wrong soil environment, then they can produce poor growth.

Top tips

  • Firstly, check the acid/alkaline balance of your soil with a simple pH Test Kit (available from all good garden centres). If the results show your soil is naturally acid go ahead and plant, if it’s neutral or alkaline then you’ll need to use a specialist compost.
  • When buying plants, check the care label to see what type of conditions they prefer. If they are acid-loving you’ll need to make sure you have the right compost, feed, etc.

FAQs

Can I re-use my patio pots year after year?

You can certainly re-use them, but it’s best to tip out all of the old compost and then wash the containers thoroughly with warm soapy water, followed by a good rinse with a solution of cold water and a garden detergent. It’s important to do this because your existing compost may be harboring vine weevil larvae and other garden nasties. It’s far better therefore to have a spring clean and thus minimise the risk of pests and diseases infesting or infecting your new displays.

Why can’t I use my own garden soil to pot up plants?

garden soil doesn’t hold as much water as a good potting compost and so you will have to water more often or your plants will suffer. Soil also lacks essential nutrients and so plant growth will be slower. Garden soil may also harbour pests and diseases.

I’ve opened up my compost and it looks like an insect has laid eggs in it

This is most likely to be the small round coloured granules, which are the controlled release fertiliser, that when squeezed will pop open releasing a liquid which is the fertiliser concentrate. The fertiliser cases have a semi permeable membrane, which allows water inside to dissolve the nutrients within them. The nutrients are then released back into the compost in a soluble form for the plants to absorb. The cases will naturally breakdown in the compost over time.

How can I find out whether my soil is suitable for rhododendrons?

The best way is to use a pH soil testing kit. If the results show your soil is naturally acidic then rhododendrons, azaleas, camellia and the like will thrive. If it’s neutral then you can still plant away, but feed with a special plant food that’s been formulated for acid-loving plants such as Miracle-Gro Water Soluble Ericaceous Plant Food. If you’ve got alkaline soil then your best bet is to plant the rhododendrons in a container filled with a suitable ericaceous compost – try Miracle-Gro Azalea, Camellia & Rhododendron Enriched Compost - and then feed with an ericaceous plant food throughout the Summer.

Can you explain the differences between the John Innes composts?

John Innes Composts are soil-based growing media made from a mixture of loam, sand or grit and peat with increasing amounts of plant foods added. Levington John Innes Seed Compost contains the smallest amount of nutrients as this encourages the best germination and growth of tiny roots and shoots. Levington John Innes No.1 Compost has slightly more nutrients and is for transplanting seedlings. Levington John Innes No.2 Compost for when you are potting up small plants and Levington John Innes No.3 Compost has the most nutrients, as this is designed for final planting up of plants ready for display or cropping.