Hibiscus plants are widely recognized for their tropical appeal with the enormous, vibrant blooms that add a touch of the exotic to any garden. However, most of us have associated the flower with warmer climates, thus making it appear to be the kind of plant that would not be too hospitable in areas with colder winters. For those living in USDA hardiness zone 7, hibiscus may seem like a challenging proposition when it comes to growing it. Thankfully, some species of hibiscus are cold-hardy enough to thrive even in these cooler zones. This article covers the different cold-hardy species of the hibiscus plant, along with the guidelines for successful cultivation within zone 7, and shares some useful tips on how to care for it throughout the year.

Cold Hardy Hibiscus – What is it?

Cold hardy hibiscus refers to species and hybrids of hibiscus that have more cold tolerance, thus would be able to survive winter freezes common in zone 7. Whereas the tropical Hibiscus Rosa-sinensis does not tolerate cold and can be grown only in containers or as annuals in colder regions, cold-hardy types such as Hibiscus moscheutos, Hibiscus syriacus, and hybrids from the Rose Mallow family grow well under freezing winters.

Following are three of the most popular kinds of cold-hardy hibiscus that should do well in zone 7:

1. Hibiscus moscheutos (Swamp Rose Mallow)

Native to North American wetlands but adaptable to many garden situations, Hibiscus moscheutos boasts enormous flowers reaching up to 12 inches across. The huge, tropical-looking flowers come in white, pink, and red and begin showing up in midsummer, really making a splash in any garden.

2. Hibiscus syriacus (Rose of Sharon)

Rose of Sharon is cold-hardy and a great choice for zone 7. The flowers are smaller but even more prolific than Hibiscus moscheutos, and the colors include white, pink, purple, and blue. It flowers in late summer through early fall and extends color in your garden well into autumn.

3. Hibiscus hybrids (‘Luna’, ‘Kopper King’, ‘Lord Baltimore’)

Many varieties have been hybridized for cooler climates, and one of the more popular is the Luna series. These plants are much shorter, bushier plants that bear larger flowers and can become a great addition to the smaller gardens. Another well-known hybrid is ‘Kopper King’, featuring outstanding copper-colored foliage with massive, bright pink flowers in which your garden gets the benefit of color along with texture.

Knowing Zone 7

USDA hardiness zone 7 is defined by average minimum winter temperatures between 0°F and 10°F (-17.8°C to -12.2°C). Zone 7 covers a good range of areas throughout the United States, from Virginia to Tennessee and North Carolina, Oklahoma, California, and so on. As a rule, this zone will give one a moderate growing season with hot summers and generally mild winters compared to colder areas.

Being in zone 7 isn’t necessarily ‘extremely cold’, but one has to be pretty particular with just the right plant and proper plant care especially if the plants are the kind that is usually grown in warm climates – just like this hibiscus plant.

Cold Hardy Hibiscus Planting in Zone 7

1. Choosing the Right Location

Cold hardy hibiscus plants just love the sun; hence, choosing a location for the plant that receives at least six hours of direct sun each day is quite crucial in attempting to urge some fantastic blooms from this ornamental plant. Steer clear of areas with very heavy shade, which can diminish some of the flowering potential of your plant.

Also, hibiscus planted in a well-ventilated area avoids fungal diseases which generally occur when the air is cool, moist, and not circulating. Cold hardy hibiscus, such as Hibiscus moscheutos, is very fond of relatively moist conditions of the soil, so if possible, plant it near water features or where the soil is fairly moist.

2. Soil Requirements

Cold hardy hibiscus prefers well-draining, rich organic matter soils. Heavy clay soils should be amended with compost or peat moss to facilitate drainage. Plants do well in slightly acidic to neutral soils: pH ranges from 6.0 to 7.0. Pre-planting the site with organic material such as compost or well-rotted manure promotes nutrition and improvement in the soil structure.

3. Planting Time

Plant cold hardy hibiscus in the spring-after the last frost date. Spring planting allows the entire growing season for the hibiscus to get established with a strong root system before the heat of summer and cold of winter.

Container plants should have their root ball lightly teased outwards to encourage a wider spread of roots. Plant them at the same depth they were growing in the container.

Cold Hardy Hibiscus Care in Zone 7

1. Watering

Cold hardy hibiscus plants are thirsty plants that love moisture, especially Hibiscus moscheutos, tolerating wet conditions of the soil. However, none of them like to sit in water. The deep and frequent watering is recommended during the growth season, usually hot summers, to be able to keep the moisture of the soil consistent. They need mulching around the base to retain soil moisture and keep the roots cool during summer.

Watering regularly is important for newly planted hibiscus plants as they establish themselves in the first year. Plants that are well-established can tolerate short droughts; it is always advisable, however, to keep them under consistent moisture.

2. Fertilization

Hibiscus plants are heavy feeders and love to be fertilized throughout the growing season. Give them a dose of slow-release, balanced fertilizer in the spring for new growth to begin and to continue blooming profusely. You can also use liquid fertilizer every four to six weeks throughout the growing season for a nutrient boost.

Choose a high-phosphorus fertilizer, as this promotes flowering. Avoid high nitrogen levels, as this will result in lush foliage at the expense of flowers.

3. Pruning

Pruning of your cold, hardy hibiscus is necessary for its healthy growth and good flowering. Cut dead stems back by about 12 inches from the ground during the late winter or early spring, before any new growth has started, to give way for new growth to sprout from the base, allowing it to keep looking neat.

You can also do some deadheading in the summer to make sure blooms keep on coming. This is by no means a necessity, but it keeps things looking nice and clean and may encourage further flowering.

4. Winter Protection

Cold hardy hibiscus can be dependable in zone 7 but still appreciate a bit of special care to see them through the most severe winter periods. A layer of organic mulching material around the base, placed 2-3 inches deep, like straw, leaves or compost, will insulate the root and shield it from frozen temperatures.

While the hardy Hibiscus moscheutos and other types will die back to the ground in winter, it will regrow from the root in the spring. Do not cut back the plant before early spring as the old stems can protect during the winter season.

5. Pests and Diseases

Cold hardy hibiscus plants are pretty hardy but can be also irritated by the usual suspects: insects like aphids, spider mites, and whiteflies. These can be controlled with insecticidal soap or horticultural oil.

Overwatering may bring about a couple of the fungal diseases, which include rust and leaf spot. Ensure proper water regulation is done and sufficient air movement around the plant. In case of need, prevention or treatment with a fungicide shall be conducted appropriately.

Conclusion

With proper care and preparation, cold hardy hibiscus may prove to be successful in zone 7. These varieties add a touch of the tropics to areas with cold winters and give the gardener an opportunity to experience their large flowers all summer and into fall. You can have the bold beauty of hibiscus in your yard year after year. Plant appropriate species in suitable locations and with correct care.