On 30/04/2021 21:38, Derek wrote:

Some people say mixing old coffee grounds into garden soil makes it
better for growing plants.

Should be used with great care, Coffee plants exclude a substances
that inhibits seedling growth, this is their way of making sure their
seedlings have a better chance of survival
James Wong of GQT did a number of experiments a few years ago and
proved that coffee grounds are not good for the soil

That seems a bit OTT.

Inhibiting unwanted seedlings could be a benefit from using coffee
grounds like that. Foxglove, poppy and annual weed seedlings are too
plentiful as it is - a bit of inhibiting is not a problem.

The only common UK plant I can think of that seriously causes problems
is walnut which really does have a potent anti competition compound in
its roots called juglone.

A few handfuls mixed in with the compost heap will not be a problem,
but a sack full for the local coffee shop would be

Last week's GQT had this as its second question,

As for it stops slugs, plenty of videos showing that it does not stop
them, easy to see why, slugs travel on the mucus they produce, so
nothing stops them accept a water barrier, (and even then they may go
under it)

Although there are it is still better than nothing and relatively
harmless to everything else.

--
Regards,
Martin Brown