repotting containers

anne.baines

new gardener here. i understand that I cant reuse compost so should i repot all my containers every year. and can i check that means take all plants out and into new compost!! is this right

Mrs-B3-Southampton,-Hants

Welcome.
With large containers you scrape off the top couple of inches and put new on.
Plants in small pots get more compost when they outgrow the space and you put them in a bigger pot.

The reason spent compost is not used again is because all the nutrients have used and pathogens may have been acquired.

rachelQrtJHBjb

I guess it depends on what you're growing in containers. Is it long-term/permanent planting or are we talking annual displays?

If, for example, you had a large pot but planned to copy Monty with a summer-only display of (say) substantial cannas or dahlias, with smaller plants beneath, then I would replace at least half of the compost and add a slow-release fertiliser for the growing season. 

shane.farrell

You certainly can use old compost. Some ideas -
- mulch your beds

- use some mixed with sharp sand, good topsoil or new compost when making a potting or seed mix
- dig into a new planting hole

Even old compost creates better soil and improves structure and drainage.

Buttercupdays

I wouldn't use it for seeds though, unless there was no choice, as last year. There is the risk of pathogens, as already said, including fungal spores that might damage the seedlings, and you can virtually guarantee some weed seedlings, a nuisance, especially if you sow mixtures. Fine for older plants though.

shane.farrell

True about pathogens and weeds re seeds although I take a more cavalier approach and plants have to be tough enough for my garden 🙂
I don't do that many and try to put single seeds in the middle of the cell so I can tell if it's 'my plant' or not 👍

Obelixx

Potting composts contain, at best, enough nutrients to last 90 days so permanent pots need an annual top dressing in spring plus additional feeds thru the growing season.  If you re-use such compost without beefing it up with extra nutrients your plants will starve so it's a false economy.

Pots filled with temporary seasonal plays are best emptied out and fresh compost added before the new plants go in.   Any compost tipped out can be used as a mulch to improve soil texture or added to the compost heap.  In either case, micro-organisms and an assortment of birds, insects and other small creatures will recycle the compost and any pests or seeds in it.