There are many species of Hibiscus in cultivation, and some of them are considered winter hardy in the Portland area. This feature outlines year-round care instruction for those that are not; primarily, but not exclusively, Hibiscus rosa-sinensis.
Hibiscus rosa-sinensis is the most commonly grown of the tender Hibiscus, and is the state flower of Hawaii. They are medium to large shrubs that we usually grow as small container plants.
Hibiscus perform best outside in summer, placed in part to full sun. As a container plant, they will dry out rather quickly, especially if the shrub is full of leaves and healthy. Do not let them fully dry out; water before they wilt for best results.
Do not, however, water until the surface of the soil has dried. If watered and fed regularly, most Hibiscus will bloom quite oHen throughout the summer. You will get the best results from regular doses of a water-soluble fertilizer, but organic options can work too. Pruning can be done in summer if it is necessary to control the size, but it does temporarily interrupt the blooming.
Insect pests can be a problem for Hibiscus rosa-sinensis. Aphids, spider mites, and whiteflies are all fairly common problems, with scale and mealybugs putting in appearances too. For small plants, physical washing can help with aphids or spider mites.
Insecticides, particularly systemics, can give fairly good layers of defense. Topical insecticidal sprays may need regular applications.
At some point, you will have to move your Hibiscus rosa-sinensis indoors, either to the house or a heated greenhouse/sun room. Though it is possible, I do not recommend overwintering them in garages, sheds, or basements. If they are to be in the house, find as bright a spot as you can and move them inside before any real threat of frost. If it is possible, acclimation is beneficial, though not necessary.
They will drop some leaves, sometimes quite a few, and bloom a lot less. The brighter your spot, the better the plant will be. Water moderately; avoid either extreme. Do not fertilize at this time, or fertilize sparingly. They can make a pretty good houseplant in bright light, growing moderately well and even blooming occasionally.
If you can move them into a heated greenhouse or sunroom, there should be little or no shock to the plant. They will continue to perform almost as well as they did in summer. The lack of natural light (short, cloudy days) will be their only barrier. Again, water moderately, avoiding extremes. You can continue to fertilize in such conditions, and the plant should continue to flower.
Whether in the house or greenhouse, beware of bringing a lot of insect pests into a previously pest-free environment. This can be a problem for those who grow assorted tropicals.
At some point aHer danger of frost is past (usually well into May if you want to play it safe) you can move your Hibiscus back out to its summer location. The transition shock should be minimal unless you move it out too early, into cold spring wind and rain for example.
The plant’s water needs may increase gradually, and sometimes dramatically once the weather breaks and your plant is back outside in warm sunshine. Start fertilizing again, possibly in April to May before you move the plant out, and certainly once the plant is out and the weather is fair.
If you choose not to move your plant outside it can be kept permanently as a bright light houseplant or greenhouse plant. In a bright indoor location they can stay fairly full and may bloom occasionally, and in a sun room or greenhouse they will bloom prolifically.
There are some other species of Hibiscus that some gardeners grow around here. Hibiscus acetosella can be treated much the same as above, though it sometimes isn’t attractive in the winter indoors. Hibiscus trionum does not make a good houseplant, but it blooms prolifically in summer and can easily be re-grown from seed each year like an annual.
Abutilon hybridum is a Hibiscus relative that can also be taken in for the winter, though they tend to have weak floppy when growth indoors, and don’t usually bloom inside. Nonetheless, they can be carried over in much the same way as described above.
Anisodontea capensis makes a rather poor houseplant, and might be best grown simply as an annual unless you have a sun room or greenhouse. Some other genera and Hibiscus species are winter hardy and should be left outside; those are not intended to be within the scope of this care sheet.
From Aloe to Zygopetalum, we cover the alphabet with choices for your home or office; plants for your brightest window or your darkest corner, those that willa love the humidity near your shower or prefer a dry, sunny spot. Orchids, succulents, indoor bonsai and cactus. We have them all. You'll find our featured houseplants below. We carry our largest of houseplants at our Division location. This is only a brief list.