Choosing the correct compost is important as its make-up must reflect the needs of different plants at various stages of their life cycle. This is Nathan James Dodd's guide to the various composts that match a plant's individual requirements.
Different composts are designed to give optimum results in a variety of situations from sowing seed to bedding, containers and house plants.
Seed And Potting Compost
Whatever brand you choose, it is worthwhile investing in a specialist soil based seed compost. This is because seeds don't require the amount of nutrients found in multi-purpose compost and you'll want to give them the maximum chance of germinating.
John Innes No.1, 2 and 3 each have various nutrient and fertiliser formulations for potting on seedlings or rooted cuttings with richer blends suiting more mature plants in pots and containers. Due to its weight and firm anchorage, John Innes is particularly suitable for permanently planted trees and large shrubs.
Multi-purpose composts, with a balanced mix of nutrients and good water retentive properties, are marketed to achieve similar results but in one package.
Peat Free Compost
Peat has traditionally been used in commercial composts. However environmental concerns have been raised regarding this finite natural resource, these range from the destruction of natural habitat to the carbon footprint its importation creates.
Made from coir, wood fibre and various composted organic matter that would have been sent to landfill, peat free or peat reduced compost has increasingly been seen as a viable alternative.
Governmental targets have included the phasing out of peat as a growing medium by 2020 and the percentage used has in fact dropped from 70% to an average of 46%. However because gardening is increasing in popularity, the total amount extracted hasn't significantly reduced.
Although peat free compost producers are continually improving their product, some died in the wool peat users, although they may see the environmental sense, still need convincing that peat free compost is as efficacious.
Many plants such as orchids benefit from specialist composts and feeds formulated specifically for their particular needs:
Ericaceous compost is essential for acid loving plants such as Camellias, Rhododendrums, Azaleas and Heathers.
Citrus Compost must be free draining as the root system of lemons, oranges, limes etc enjoy dry conditions that are nutrient rich and slightly acidic.
Cacti Compost is very gritty and drains easily. Its porous nature and essential nutrients will allow your cacti to thrive.
Bonsai Compost has less nutrients than other compost but has the correct balance of aeration and water retention for a healthy root system.
Orchid Compost is free draining as they hate waterlogging and love an aerated growing medium that this type of compost provides.
Aquatic Compost should be loam that is heavy enough to keep the plant basket in place, also present will be a slow release fertiliser that won't leach into the pond.