What flowers are actually in season in autumn
Autumn is one of the most interesting times of year for flowers, partly because people don't expect it to be. The assumption is that spring is the season for flowers and everything else is a compromise. That's not really true, and autumn in particular has a lot going for it.
September: the tail end of summer and the start of something else
September is still dahlia season, and dahlias are at their peak in late August and early September. You'll also find the last of the sweet peas and lisianthus, and the beginning of the chrysanthemum season. Rosehips start appearing in hedgerows and at the market, and they're useful for adding texture and a bit of colour to arrangements without adding much cost.
Nerines start coming in from mid-September. They're a bulb flower, related to amaryllis, and they have a slightly exotic look that works well in autumn arrangements. They last well in a vase, often ten days or more.
October: the richest month
October is probably the most varied month for flowers in the whole year. Dahlias are still going (until the first frost), chrysanthemums are in full swing, and you start to see dried and preserved materials appearing at the market: honesty seed heads, dried grasses, cotton stems, and various seed pods.
This is also when the foliage gets interesting. Autumn leaves, berried branches, and dark-leafed stems add depth to arrangements in a way that the green foliage of summer doesn't quite manage.
November: quieter but still good
By November the fresh flower range narrows. Chrysanthemums carry through, and you'll find carnations, alstroemeria, and whatever the market has brought in from further afield. It's a good month for dried arrangements, which hold up well in the colder, drier air of autumn and winter.
If you're planning flowers for a November event, it's worth having a conversation with your florist early so they can plan around what will realistically be available.
The honest answer is that autumn flowers reward flexibility. If you're open to what's actually good that week rather than committed to a specific variety, you'll get better flowers.