Red cordyline help please, one is looking very poorly!

[LMGTFY]

Please can anyone help? I have 3 red cordylines in large built planters around 2ft high. They are built onto patio slabs if I remember rightly but have hardcore, soil, topsoil, compost then large pebbles on top. They've been in place for around 5 years and have done very well, growing large and healthy... however one is looking very poorly all of a sudden, around 80% now looks like 'bottom leaves' as I think of them, is there anything I can do to revive it? Thanks if you've read all that waffle!

These are pretty hardy i think. I wonder if one of the planters has got a huge ants nest in, which is disrupting the soil and damaging the roots? Or maybe it has got much dryer than the other two and you've only just noticed the dead leaves? From what I have found, it's hard to actually kill them. I would wait until the bottom leaves are properly dry, then peel them off. Scrape off some top soil and replace with some new compost and keep it watered sufficiently ( but not too much, they can stand it pretty dry). You can get nematodes from green gardener to water in to kill off ants nests.
Someone else might have better ideas.

Thanks, I'll take a good look tonight and see if there is something going on below the surface, I have some fresh compost so will top it up and see if that helps, I haven't seen any ants but then I haven't moved the stones yet!

My guess is that they're suffering from drought/heat stress. Cordylines are tough but even they need a little love sometimes! My guess is that they've grown and grown and now they may be outgrowing the pots. 2ft isn't that deep for a really large plant, especially if it can't get its roots down into the soil because it's on paving slabs.

If this is the case, the solution is to give them more space. If there's a lot of hardcore in there, you might want to take a bit of it out and add more compost with some grit added for drainage. However, in the long term, you might need to think about a larger contained for them! (Or ditching them and buying smaller plants).

I would also make sure they get a feed and plenty of water immediately.

have a look for vine weevil grubs in the pot

its recommended an annual pesticide treatment to try and stop them from eating all the roots on a pot confined plant