There's such a choice of  containers to grow in!

There’s such a choice of containers to grow in!

It’s getting to that time when we plant up containers – with annuals, or perhaps longer lasting plants. Which type of compost should you use?

There are two main types of compost: soil-based (John Innes) and soil-less, which may be based on peat or a peat substitute such as coir or perhaps recycled household waste. In addition, depending on the drainage requirements of the plants you’re placing in containers, you’ll need to add some horticultural grit, Pearlite or similar. And some plants- bulbs for example- like a mix which is less nutrient rich, light and leafy- so add in plenty of leaf mould.

All containers need some means of letting excessive water escape- in most pots there’s a hole in the bottom and permeable liners (or a few holes punched in a piece of plastic) in hanging baskets will achieve the same result. But don’t forget to rest some pieces of broken pot or tile over the drainage hole in the bottom of the pot to avoid the compost washing out.

Plants like this Box ball requires a soil-based compost to thrive long term

Plants like this Box ball requires a soil-based compost to thrive long term

Soil-based composts

These are heavy, retain water well and provide a long-lasting supply of nutrients. They are the best choice for permanent plants in containers and for plants that grow tall and are top heavy. For permanent displays, use john Innes Number 3 because of its high level of nutrients.

Soil- less composts

These are lightweight, clean and easy to handle, but dry out quickly and contain few nutrients. Soil-less composts are best for temporary displays, such as bedding plants and hanging baskets. Peat-based composts are the most consistent in quality, though alternatives are improving all the time (especially some of the recycled organic matter types) and do not deplete the landscape like peat-based types.

Plants like Pelargoniums (these are in the courtyard at Old School Garden), require a very gritty soil-less compost.

Plants like Pelargoniums (these are in the courtyard at Old School Garden), require a very gritty soil-less compost.

Source: ‘Short cuts to Great Gardens’- Reader’s Digest, 1999

Old School Gardener

 

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