watering
Water regularly during the summer season, paying particular attention to gladioli in containers, as these will dry out more readily. On well-drained soil, extra watering will be required – adding a mulch of compost will help to retain moisture.
fertilising
Apply a high potash feed, like comfrey pellets or tomato fertiliser, every two weeks as soon as the flower spikes emerge and until at least three weeks after flowering. This is essential on poor soils as flowering can diminish in successive seasons.
staking
Tall varieties of gladioli will need to be staked. It’s better to push the canes into the ground before planting the corms to avoid damaging the bulb.
deadheading
To tidy up each stem while the gladioli are in flower, remove faded florets to keep the stem looking fresh. Cut the stem back when all flowers have opened and leave the leaves to continue to photosynthesise, providing food for the corm for the following year.
propagating
Over time, clumps of gladioli get congested, with new cormlets forming every year – this results in weaker plants with lots of foliage and diminished flower spikes.
You need to dig up and divide the clumps every few years and select the best corms for replanting. This will give you more plants with healthier growth.
overwintering
It's always said you need to lift your gladioli, and that like dahlias, they'll be frosted if left in the ground. I’ve grown them at Perch Hill for years and I've never lifted them.
Instead, I mulch them deeply with 6-7cm (2.5in) of compost to give them an insulating duvet over their heads in late autumn.
You should be safe with this in the south of England and the western fringes of the British Isles, but in colder areas, they will need to be lifted and brought undercover.
If they are growing in pots, stop watering when the leaves turn yellow, cut them down to about 10cm (4in), then dig the corms out of the compost and place in trays somewhere cool and dry for a couple of weeks.
After this time, shake off any loose compost, snap off the remaining stem and any shrivelled corms that may be attached to the main healthy corm. The same applies to corms that are being lifted from the ground.
The dry healthy corms can then be stored somewhere cool and frost free over the winter – hang them in a mesh bag for good air circulation.
Any new small cormlets that have formed around the base of the main corm can be picked off and potted up. These will need to be grown on for a few years before they reach flowering size.
