Glad of gladioli advice!
Many thanks for your latest message, this time concerning gladioli corms – and I’m glad to hear my advice on the monkey puzzle tree (Araucaria araucana) came in helpful.
Some gardeners (especially those in the south of England) will leave the corms in the ground, covered by a thick (at least 5cm) layer of light compost. This is usually sufficient to stave off winter frosts and the corms will shoot again the following spring for summer flowering.
However, what you gain on not having to lift the corms you lose on productivity as it’s good practice to dig up and divide the corms every couple of years for continued flowering. This enables you to replant the best, newer corms and stop huge clusters developing which will all compete for nutrients to the detriment of flower production.
My advice would be to lift the corms once the leaves turn yellow and brown and snap off the stem. Dry out the corms, dust them with sulphur to prevent rotting during the winter then divide them, keeping the newer ones and discarding the oldest if you have too many. Keep these corms dry and cool throughout the winter (frost free is essential) before planting out in late spring when some evidence of shooting is present.
Hopefully this helps but as ever, please feel free to ask any questions and I’ll do my best to advise.
Thanks again and the best of luck with your garden during late summer and autumn.