(📸 Michel VIARD from Getty Images)

Most of us become fixated with tropical hibiscus (Hibiscus rosa-sinensis) after visiting exotic locales such as Hawaii or Mexico and come late summer many gardeners typically shop for Rose of Sharon (Hibiscus syriacus) at the garden centre, but surprisingly very few people seem to have any experience with perennial hibiscus until they stumble onto their massive blooms (which can range anywhere from 6-12” across) and ask "What is that?"

Most perennial hibiscus are complex hybrids bred from several species including H. moscheutos (Swamp Rose Mallow), H. laevis (Halberd-Leaf Mallow) and H. coccineus (Scarlet Hibiscus), all of which are native to temperate North America. In the wild they are generally found in wetlands or stream sides, and they are all herbaceous perennials that die back to the ground each winter and regrow new stems the following spring.

(📸 Proven Winners | Hibiscus 'Summerific Holy Grail')

In my opinion there really should be a lot more of these specimen perennials planted in local gardens and with that in mind, here are the answers to the most common perennial hibiscus questions that I receive.

Are perennial hibiscus hardy?

In a word, yes, as the species range from USDA zone 4-6 and most of the hybrids are rated at USDA zone 4, which is hardier than the shrubby Rose of Sharon or Hibiscus syriacus.

How much sun do perennial hibiscus need?

When do perennial hibiscus flower?

(Hibiscus 'Carousel Giant Red')

The species generally bloom from July to September, with many of the hybrids lasting well into October, depending on the weather.

How much water do perennial hibiscus need?

(Hibiscus 'French Vanilla')

Perennial hibiscuses are best located in moist soils, but if that’s not possible, then they will need regular watering (1-2” per week) and should never be allowed to dry out when growing or in bloom.

How tall do perennial hibiscus grow?

What flower colours are available?

(Hibiscus 'Strawberry Swirl')

Red, pink, white and creamy-yellow are typical bloom colours, many with a contrasting eye or veining. These can be further enhanced by variegated or rich burgundy-black foliage available on some cultivars.

Do you have to deadhead the spent blooms?

Deadheading is not necessary, but it will improve the overall appearance and extend the flowering season.

Is pruning necessary?

(Hibiscus 'Starry Starry Night')

Yes, but only once a year. Leave the old stems intact for winter and cut these down to 4-6” using loppers or a small handsaw in spring, when the new shoots emerge from the soil.

When do you fertilize and with what?

Fertilize in spring once the new shoots emerge using a slow release such as 14-14-14. Be warned that this is one of the last perennials to emerge in spring, with many gardeners often prematurely discarding what they thought was a dead plant.

Do perennial hibiscus require winter protection?

Despite being so cold hardy, young plants should have their crown mulched heavily for their first winter and even established clumps will benefit from this.

Are perennial hibiscus good pollinator plants?

Perennial hibiscuses are much sought after by both bees and hummingbirds for their delicious nectar.

Well, there you have it. Easy answers for an easy-to-grow perennial that is just waiting to be planted along your bare fence line or at the back of your soon-to-be spectacular mixed border. Regardless of where you plant them, there’s no way your neighbors won’t be jealous of those massive late summer to autumn blooms.

All images Copyright 2024 MK Lascelle, except those already credited.