Experts and BHG readers answer.
Need a sbstitute for crocosmia.
Thanks for writing. Bee balm may be one of your closest choices --- it offers scarlet-red flowers for a month or two (July-August) if you're good about deadheading it (removing the faded blooms). 'Burgunder' (aka 'Burgundy') gaillardia is one of the longest-flowering red-blooming perennials for sun that I know of (June-September), though the flowers aren't nearly as brilliantly colored. Dwarf varieties of hardy hibiscus such as 'Luna Red' also bloom for quite a while (July-September), though their color and texture is very different.
Some of the red penstemon varieties (such as Penstemon pinifolius) also have blooms for several weeks in summer and bright reddish coloration.
Bee balm: http://www.bhg.com/gardening/plant-dictionary/perennial/bee-balm/
Hardy hibiscus: http://www.bhg.com/gardening/plant-dictionary/perennial/hibiscus/
---Justin, Senior Garden Editor, BHG.com