Colours that do often go well together are these hot combinations
Kniphofia (Red Hot Pokers) a structural addition to any mixed perennial bed. These, adding height, don’t need staking although they do prefer a sunny spot. These perennials are quite tolerant of dry conditions. They will need water but don’t sit well in wet soil so a well drained consistency is needed. Periodically, this perennial needs dividing to keep the vigour and flowering ability. The size also needs control. They can become invasive and do take up room.
Helenium (sneezeweed) offer interest to beneficial insects. This perennial is fully hardy and tolerates quite severe conditions. Although they look rather like a sunflowers they are not. This perennial prefers an acidic soil and flowers during the summer. These daisy like flowers will offer an enrichment of oranges, reds and yellows. It is clump forming so it can be divided. These are usually tall and suit most borders but H. ‘Mardi Gras’ needs to be at the front, it is smaller.
Monarda (Bergamot) the foliage is scented and beneficial insects love this. The soil needs to have substance but not water retentive, good drainage is needed. Its performance is dependent on full sun. M. ‘Cambridge scarlett’ however, will do well in shade. It will flower throughout summer into early autumn.
Hemerocallis spp (DayLillies) the flower that only lasts a day. However, the flowers come in such profusion, this perennial offers different flowering varieties with some quite early H. lilioasphodelus to late H ‘Frans Hals’. The cultivars have improved and now day lilies are more robust to adverse conditions and available in many more colours (hot) and (cold). A summer flowering perennial, its period is quite lengthy and doesn’t really require any attention, cutting back spent stems and maybe division in spring. This will produce more plants but their energy will be restored too.
Rudbeckia (Black eyed Susan) is a perfect addition to the perennial bed although these do prefer sun. Some partial shade is O.K. but not full, they will not do well in a chilly corner. You can divide although the seeds will come true too. It will flower throughout summer to maybe September in the right conditions. These perennials are hardy but if dividing do so this before winter (so they can acclimitise themeselves) or in spring after the cold snap. It is beneficial to do before but not essential.
An interesting discovery only recently unearthed is the Isoplexis plant. It is in fact a foxglove, but a tropical one. The canary island foxglove will provide you with a flowering period when most have ended. Late summer to early autumn. It is also effective in attracting beneficial insects. Strangely, for a tropical plant it is quite hardy tolerating temperatures – 5. It will need some protection certainly from cold winds though. It will give both attractive flowers and foliage. Full sun or maybe partial sun at the least.
A very hardy specimen which without fail will perform is Crocosmia / Mobretia as it is otherwise known as. There is common variety which does the job but there many cultivars now which have particular charcateristics. C. X Crocosmiiflora ‘George Davidson’ which has yellow flowers. C. ‘Emberglow’ which has a combined orange and yellow. C. ‘Lucifer’ is the most popular. The colours of red and orange will provide effective drifts in most perennial borders. It is a very hardy plant. It will survive in all conditions, all soils. It’s a “corm” so the cluster of tightly packed bulbs can easily be divided. Over the dormant period you might cut the spent growth off but otherwise self sufficient, you will probably find yourself reducing the cluster and pulling it out.