Recycling has never been as enthusiastically received, and never more necessary, than now. This applies to garden waste, too. But when it comes to reusing old potting compost, is it a good idea? Well, a guarded yes and no.
Old potting compost cannot be reused for seed sowing or propagating unless it has been effectively sterilised because it might contain the eggs of insects (like vine weevil or flies), or pathogens that might lead to disease.
Related: how to improve your soil.
Unfortunately sterilising soil involves high temperatures and it’s a smelly process - rather like fermenting hops. So this is not at all viable for many home gardeners, although there are sterilisers on the market.
Reusing loam-based compost
You can recycle friable loam-based composts by adding them to the ground to improve soil structure, or using them as a moisture-retaining, weed-suppressant mulch.
If you add a fertiliser to the loam-based compost you can also pot up mature plants with it. I have a spent-compost heap close to my own shed and greenhouse that I use to pot up divided perennials.
Related: how to make a compost heap.
Avoid peat-based composts
Gardeners care about the environment and extracting peat is known to be damaging to plant species and habitat. So we should look at other forms of compost in an attempt to find one good enough to replace peat.
The government has set 2020 as the date when all compost sold to gardeners must be peat-free.
Peat-based composts are impossible to rehydrate once they dry out. They can form dry balls in garden soil so you need to take care how you use them. They are not as easily recycled as loam-based products which contain sand, silt and clay.
Green waste recycling
A significant change has occurred in recent years in the way local councils deal with green waste. If you use your local council waste station, you’ll be aware that they are composting green material from gardens, sterilising the product and then selling it on, rather than putting it into land fill.
Many councils are selling it back to their residents and others are supplying commercial companies.
So there is no reason why you couldn’t put spent compost straight into a green waste bin – it will still be useful. Contact your local council to see what measures they are taking – and if they’re selling their own bags of compost.
Related: how to help your local area be more environmentally-friendly.