Some of the earliest Gladioli to flower in the UK are the winter growing Gladioli Tristis.
In a sheltered part of the garden they will survive -5 apparently, although they have survived lower temperatures here for me. The oldest known first cross was between G Tristis and
G Cardinalis, The Bride was introduced in 1823, and one of the first ornamental plant hybrids to enter commerce. A more recent introduction is Galaxian. I believe there was a breeding program initiated by Israeli breeders and Claudia was a result of that.
Their hardiness, height, small flowers are a big draw for me, combined with the potential to extend the flowering season. They are perfumed, but very few crosses take this characteristic. Tristis pollen was saved last Spring and put to the best of my Summer flowering plants, first results expected next year, but I have already sown a few seeds to get a feel of what's coming next year.
But this year I have frozen pollen from last years choicest plants to put to these, weeks to wait!