Compost For Indoor Plants

Having selected a new pot for your indoor plant, be sure to use the right soil to fill it. As suitable loam is not easy to obtain and its quality may be extremely variable, use one of the commercial corn-posts which do not contain loam. These soil-less composts are based on peat and have a great many advantages when compared with their soil-based counterparts.

1. They are easily obtained in bags of varying sizes.

2. They are already sterilized when you buy them, so are ready to use.

3. They are lighter and cleaner to handle.

4. Their quality is consistent.

5. Special types are available to suit plants with special requirements, e.g. lime-free for Azaleas. They can also be obtained with varying fertilizer content.

indoor-plant-compostProprietary composts will generally contain sufficient constituents to provide normal plant nutrients for a period of eight weeks and feeding is not necessary, or even desirable, during that period. For a few plants, the period may vary slightly, so you should always follow the manufacturers’ recommendations.

The composts are normally bought packed in polythene bags, and usually in a rather dry condition.

Most of the peat composts are rather difficult to wet although some, such as ‘Baby Bio’ composts, do contain a wetting agent to make it easier. If possible, open the bag, roll back the top, prick for drainage and leave it out of doors until a downpour of rain does the work for you. Otherwise, smaller amounts must be dampened in a bowl before the compost is used for planting.

When you come to fill your pots, it is important that the material shall not be rammed down too firmly. Excessive pressure compacts the mixture, making impossible the efficient aeration which is vital to the fibrous plant roots. Compacting is also a first step to early waterlogging.

When you buy your compost, also obtain some crushed charcoal. Mix in some of this – enough pieces to cover a dessertspoon for a five inch pot – and it will keep the compost sweet by absorbing some of the toxic chemicals which may build up. Vary the amount of charcoal according to the size of the pot, using this example as a guide.

For indoor plants, well known proprietary brands of soil-less composts are recommended without reservation but for growers who wish to use the internationally famous John Innes composts the different mixtures are listed below.

The John Innes Composts

The Basic Mixture.

7 parts (by bulk) of damp sterilized loam obtained from turves stacked grass-downward until well rotted; 3 parts (by bulk) of damp garden peat ; 2 parts (by bulk) of coarse sand; thoroughly mixed. John Innes Potting Compost No. 2 For filling pots 10 cm (4 ins) to 20 cm (8 ins) diameter.

To each bushel of the basic mix, add 50 gm (11oz) of ground chalk.

John Innes Potting Compost No. 3

For filling pots of over 20 cm (81 ins) diameter.

To each bushel of the basic mix, add 70 gm. (21 oz) of ground chalk.john-innes-compost[6]

For most pot plants use 3 John Innes Potting Compost plus Garden Peat.

For lime-hating plants (Azalea, Begonia, African Violet, Cyclamen and Erica) use the same mixture but omit chalk from the John Innes Potting Compost.

John Innes Potting Compost No. 1

For filling pots less than 10 cm (4 ins) in diameter.

To each bushel (30 kg) of the basic mix, add 25 gm (1 oz) of ground chalk (blackboard chalk, whiting or ground limestone will do).

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