How to Grow Hardy Hibiscus

The hardy hibiscus has large trumpet-shaped flowers.

The hardy hibiscus (Hibiscus moscheutos), commonly called rose mallow or swamp mallow, is native to the American southeast. The plant resists many pests and diseases, and can survive temperatures from minus 25 degrees Fahrenheit to over 100 F -- U.S. Department of Agriculture planting zones 3 to 8. In most varieties, the leaves of hardy hibiscus are broadly triangular and the flowers are generally single. Flower colors of hardy hibiscus range from shades of red, pink or purple to white. These hardy perennials make excellent massed plantings or flowering borders for a tropical sight to your garden or porch.

Things You'll Need

• Seed-starting tray
• Seed-starting soil
• Shovel
• Trowel
• Pruning shears
• Compost
• Peat moss

Instructions

1. Check the plant label for a Latin name and zone hardiness to ensure you do not have a tropical hibiscus. Seeds can be sown about two months before your last frost in seed-starting trays. The seeds are slow to germinate, taking about two weeks. The soil for seed sprouting needs to be kept constantly wet and warm. Transplant seedlings outdoors after your last frost date has passed.

2. Clear a full-sun location with moist soil for your hardy hibiscus. The second best area is partial-shade with at least six hours sun per day. The plant is not picky about soil type as long as the ground is kept well-watered. Hardy hibiscus also does well in rainy and marshy gardens. Hardy hibiscus is attractive to butterflies, bees, other small colorful insects and hummingbirds. Plant hardy hibiscus beside a pond, on wetlands and borders for a showcase of blooms and colors over summer.

3. Dig peat moss and compost into your cleared planting location, working it in well, to increase soil acidity and fertility. Dig a hole no larger that the root ball of the hibiscus, with a small trowel. Put transplants in the ground after the last frost. Water in well.

4. Pinch off the ends of stems with your finger or pruners as the plant grows, early in the growing season. Pinching encourages fuller plants with more blooms. Hardy hibiscus bloom in midsummer. Depending on the variety planted, hardy hibiscus may grow from 2 to 8 feet tall, with a similar diameter.

5. Cut the plant off at its base with pruning shears in winter. Pile a layer of mulch up to a foot deep to keep the ground from freezing around the root system if you live in a frost region. The plant regrows from the roots in the spring.

Tips & Warnings

• The plant does not require fertilizer if grown in relatively good soil.

• The plant grows from seed easily and can self-sow.

• Propagation may also be by division.

• Hardy hibiscus is late to emerge in the spring -- wait before removing a plant you think may not have made it through the winter.

References

• University of Illinois Extension: Plant Palette - Hardy Hibiscus
• Bachman's Gardens: Garden Care - Hardy Hibiscus