Chossing the Right One

Choosing a Compost

Choosing a compost for Fuchsias is not as simple as it may at first seem.  Today there is an almost overwhelming choice of different media on the market, varying in price, purpose (specialist uses), quality and, increasingly, green credentials.  A potting compost must allow healthy root growth, letting the plant fulfil its potential.  It needs to provide anchorage for the plant and have good structure - which means open enough to allow aeration for gas exchange at the roots and drainage of water, yet also providing a suitable moisture-holding capacity.  Composts must also, vitally, deliver a steady supply of nutrients to the plant.  Many people quite rightly automatically reach for a bag of multipurpose compost, probably buying on price.  Proprietary composts will suit most needs and have been carefully developed for their stated use, but some growers prefer to blend their own to meet their particular requirements.  Using differing amounts of constituent materials alters the compost characteristics: more perlite, vermiculite, grit or sharp sand increases drainage and aeration; a higher percentage of loam makes a heavier, nutrient-rich mix for longer-term planting.

Potting composts without soil/loam are used widely in container gardening.  They consist of peat or peat substitutes, such as composted organic waste or wood fibre, mixed with sand, perlite, bark chip or vermiculite for added drainage and aeration.  These composts can be adjusted by the grower for specific needs by adding extra amounts of constituent materials.   Peat-based multipurpose compost has, since the 1960s, been the most widely used potting compost, suitable for potting and propagating mixes.  Peat comes from areas of acidic, waterlogged ground where organic matter breaks down slowly, accumulating as peat.  It is cheap, free of pathogens, of consistent performance, and holds water and nutrients well.  There are, however, serious concerns nowadays about how the extraction of peat damages natural habitats.  Peat-reduced and peat-free composts use a range of organic materials such as bark fines and coir.  Composted municipal green waste is used by some local authorities and compost manufacturers in growing media.  These are variable in performance and price.

Advantages and disadvantages: Peat-based growing media hold a lot of water initially, but dry out more quickly than loam-based composts.  Water in the peat is easily available to plants.  They tend to be well aerated and less prone to water-logging.  They are light and pleasant to handle.  They also provide a 'warm' growing medium, which gives quicker root growth.  Peat-based composts are more prone to drying out and sometimes a heavier planting medium (such as a loam based compost) will be better, for example when planting tubs for exposed situations in a garden.

Coir-based multipurpose compost consists of waste coconut fibres, mainly from Sri Lanka, with various added ingredients.  Like peat, coir is pathogen free, consistent in its performance and used for potting and propagation mixes.  It does not hold on to nutrients well, but is good at retaining water.  More expensive than peat, and sometimes contaminated with salt, coir's 'product miles' lower its green credentials considerably.

Wool-based compost, is a recent addition to the market, but is not yet available nationwide.  It uses waste wool from sheep shearing, is high in nitrogen and is moisture retentive.  Wool is often mixed with composted manure or bracken in the final product.  It is an interesting niche product and development work continues.

Loam Based
Loam is a mixture of sand, clay and silt (the three main mineral constituents of soil).  While garden soils may have high proportions of clay or sand, a good loam is the perfect mixture, and loam-based composts such as John Innes potting compost are the most easily managed medium for tubs and containers and some growers still prefer loam based mixes for potting.  John Innes composts are made from sterilised loam, peat and grit with added lime and fertilisers to standardised recipes developed by the John Innes Institute in the 1930s.  They are more expensive and heavier than multipurpose composts, providing good plant anchorage. John Innes No. 1 has the least fertiliser (for short-term pot plants); No. 2 has more nutrient (for permanent pot plants with low fertiliser needs); No. 3 has the most fertiliser (for a wide range of permanent container plants).  There are also now a few recycled composts without peat on the market that have added John Innes suitable for potting.

Advantages and disadvantages: Loam-based composts are less prone to drying out, but the water they contain may not be as readily available as in peat-based growing media.  Water-logging is more likely to be a problem with loam based composts, as they are less free draining.  They are also 'colder' and less pleasant to handle, as well as being heavier (Bags of loam-based composts can be difficult to carry).

Specialist Compost
Sowing Compost:

These have a low level of nutrients and are especially suitable for seed sowing and rooting of cuttings.  Sowing composts tend to be used by more experienced gardeners to raise their own plants.

Potting Compost:

These contain higher levels of nutrients and will support actively growing plants for around six weeks, without any extra fertiliser.  Thereafter, supplementary feeding will be required.
Potting composts are used either to re-pot plants that have outgrown their containers or for potting on cuttings which have developed a reasonable root system.  They are also suitable for use in hanging baskets and containers.

Hanging Basket Composts

Although either multi-purpose or potting compost could be used in hanging baskets and containers, growers may prefer to use a compost especially formulated for use in hanging baskets.

Hanging basket composts contain higher levels of nutrients and wetting agent.

Some hanging basket composts also have water absorbing granules.  As hanging baskets are densely planted and have a high demand for nutrients and water, these are useful features.

Levington actually manufacture a specific Geranium & Fuchsia Compost and claim it to be a rich potting compost formulated specially for growing summer flowering plants such as geraniums and fuchsias.  It is stated that it is enriched with extra nutrients that feed for up to 8 weeks and thus give more vigorous plants.  Absorbs 50% more water than ordinary multi purpose composts and incorporates a unique Waterlock system that helps to keep plant roots moist for longer.  I can't comment on this as I've never used it.

Growing Media and Additives
Various materials can be added to potting composts to alter their properties, making them more suitable for the growth of certain specialist plants.  Free-draining mixes dry out faster and leach nutrients quicker than mixes containing high proportions of organic matter or loam.
Perlite is a man-made product produced by crushing and heating a volcanic glass to 1,000c.  It expands into a lightweight shell, filled with air.  More durable than vermiculite, perlite is a lightweight alternative to grit for 'opening up' compost.  Moist perlite can also be used as a sterile rooting medium for cuttings.
Vermiculite is also man-made, produced by heating a type of clay to 1,000c for one minute, causing the mineral to expand into an open lattice structure with a dry, spongy feel.  Vermiculite is sterile, contains plant nutrients, and improves the drainage and water-holding capacity of composts.  Fine vermiculite makes good cover for germinating seedlings and rooting cuttings.
Horticultural Grit
Horticultural grit is a natural material derived from rock, with particles around 5mm or less.  It opens up compost better than sharp sand, creating spaces to allow good drainage.  It also adds weight to compost (useful for top-heavy plants), improves plant anchorage, and is lime-free, so does not raise the compost's pH .
Fine Bark Chips
Fine bark chips are cheap, with good drainage, but have a low ability to hold onto water and nutrients.  Bark is variable in its constituents and performance.  Sustainable to produce in the UK, chipped bark is common in peat-free composts.
Sand is a natural material that varies in particle size and constituents.  Coarse sands improve drainage, but fine sands actually aid the wettability of potting mixes.  Horticultural sharp sand is selected for its good mix of smaller and larger grains (3mm and below).  It is lime-free (unlike builders' sand), so will not raise pH, improves drainage and adds weight to the growing medium.
Leaf Mould
Leaf Mould is an excellent soil amendment.  It doesn't provide much in the way of nutrition, therefore it should not be substituted for fertilizer. Leaf mould is essentially a soil conditioner.  It increases the water retention of soils.  Leaf mould also improves soil structure and texture while providing a habitat for soil life, such as beneficial bacteria.

Matching your plant to the most suitable medium is key to successful establishment and growing on.  While blending your own is of use for specific needs or to suit your own watering regime, ready-mixed composts are the simplest option for the majority of growers, and the range available suits most situations.

Also Click Here to see our new page on the use of Mycorrhizal Fungi as and additive to your compost