Questions Answered Series: Rose of Sharon (Hibiscus)

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Your Questions on Rose of Sharon, Answered!

Rose of Sharon (Hibiscus syriacus) boasts massive, tropical-looking blooms that transform your yard into a garden oasis. It’s no wonder that this surprisingly cold hardy shrub has gained so much popularity among gardeners and pollinators! Whether you’ve already planted your rose of Sharon or are planning to buy one soon, you can find the answers to all your questions here. See what others are asking and learn why this shrub deserves a spot in your garden.

When Does Rose of Sharon Bloom?

Rose of Sharon (or althea) puts on an incredible display of flowers in the summer! The period it blooms depends on the variety, some blooming for weeks and others blooming for months. Long-blooming varieties will bloom from summer through fall until the first frost in optimal growing conditions. You can count on all of our roses of Sharon to bloom for months on end! 

Which Roses of Sharon are Sterile

Not all roses of Sharon are sterile. Why does this matter? Rose of Sharon is notorious for seeding and producing an abundance of nuisance seedlings. Breeders know this is a problem for gardeners, so they’ve devoted their talents to breeding varieties with impressive flowers and low to no seed. They include:

Can Rose of Sharon Grow in a Pot?

Yes, you can grow rose of Sharon in a pot or container! There are three important things to keep in mind for container plantings:

  1. Proper drainage: rose of Sharon requires well-draining soils, so select your potting media accordingly. Perlite can always be added to media to improve drainage. It’s vital that the pot or container has large drainage holes.
  2. Pot size: select the right size pots for your plant! Some rose of Sharon varieties grow to massive proportions, requiring very large containers.
  3. Lighting: place your pot in an area that receives full sun. Rose of Sharon grows best with at least 6 hours of direct sunlight a day.

Can Rose of Sharon Be Kept Small?

While rose of Sharon can withstand some light pruning in early spring, it does not grow well when continually trimmed to stay small. Cutting your rose of Sharon throughout the growing season will lead to reduced blooms and an overall stressed plant. Instead, we recommend selecting varieties that naturally grow smaller than the rest. Pollypetite® is a dwarf rose of Sharon reaching 3-4 feet tall and wide. Purple Pillar® and White Pillar® grow tall but have a narrow habit. They can reach 16 feet tall but only grow 2 feet wide!

How Do I Grow Rose of Sharon

Overall, rose of Sharon is fairly low maintenance and easy to grow! Here are our general recommendations:

Soil: Plant in any well-draining soil, high fertility is ideal.
Light: Will perform best if planted in full sun.
Water: Has average water needs, but will not tolerate sogginess.
Space: 3 to 8 feet apart depending on the variety.
Fertilizing: Has rather high fertility needs. It is best to fertilize in early spring, once the ground has thawed, with a granular rose or flowering shrub fertilizer.
Winterizing: No special treatment is required.
Maintenance: Rose of Sharon does not need regular pruning, but can be pruned or trimmed in early spring if desired. Note: rose of Sharon is late to leaf out in spring. That doesn’t mean it’s dead! Be patient.

When Can Rose of Sharon Be Transplanted

The best time to transplant rose of Sharon is when it is still dormant in late fall or early spring. Make sure you dig a wide hole around the base of the plant to ensure the shovel will not damage the roots. Carefully dig up the root ball and move to a new hole that is 2x the size of the root ball. While transplanting is okay for rose of Sharon, it can still cause some stress and will take time to reestablish. Do not be surprised if there is a slight reduction in blooms the next growing season!

How and When Should I Fertilize Rose of Sharon

Roses of Sharon are heavy feeders, meaning they need plenty of nutrients to sustain growth and flower. We recommend applying a granular rose fertilizer in early spring. Do not fertilize in the fall, as this will encourage the plant to push out tender new growth that will die in cold temperatures!

How Do I Prune Rose of Sharon

Roses of Sharon do not require any pruning! That’s what makes them so low maintenance in the garden. However, if you’d like to prune them, we recommend doing so in early spring. Don’t trim back more than 1/3 of the plant each season.

Why is My Rose of Sharon Not Blooming?

Rose of Sharon is prized for its extravagant flowers, so when it doesn’t bloom, it can be a huge disappointment! Here are a few reasons why your rose of Sharon may not be blooming:

  • Not enough sun. Rose of Sharon requires full sun (at least 6 hours of direct sunlight) to set flower buds and bloom its heart out. If you think your plant is in an area with too much shade, you can transplant it to a sunnier spot.
  • Excessive heat. Many flowering plants will take a break from blooming in excessive heat to conserve energy. If your area has experienced unusually high temperatures, don’t worry. The blooms will likely return when it cools down a bit.
  • Watering. Overwatering and underwatering can both stress your rose of Sharon, which leads to a reduction in blooms. Overhead watering and summer rains can also rot unopened flower buds. Avoid spraying the flower buds as you water.
  • Improper pruning. We do not recommend pruning rose of Sharon. This shrub blooms on new wood, which means it sets its buds on new growth in the spring. It is still possible to prune your plants in early spring if you wish, but pruning them too late will remove flower buds.
  • Pests. If your rose of Sharon has flower buds, but they aren’t opening, check for aphids. Aphids will cause the buds to rot and fail to open.

Why are My Rose of Sharon Leaves Turning Yellow?

Yellowing leaves typically indicates your plant is overwatered! Rose of Sharon requires well-draining soils and is not tolerant of “wet feet”.  Try reducing how frequently you irrigate and feel the soil before watering. If the soil feels moist to the touch, skip on watering for now. If you’re sure your plant has not been overwatered, the problem may be soil drainage.

Clay soils will hold onto water for long periods of time, suffocating the roots. Amending the soil at planting can cause poor drainage by holding onto water (we call it the bathtub effect). Landscape fabric near the base of the plant prevents soil water evaporation, keeping the soil wet for longer. We strongly discourage amending soil at the time of planting and laying landscape fabric near plants. If this is the case, you may want to relocate your plant to a new area.

Will Rose of Sharon Lose its Leaves in Winter?

Yes! Rose of Sharon is a deciduous shrub that loses its leaves in winter, even in warmer climates. You can expect the leaves to yellow slightly and drop in late fall.

Are Rose of Sharon and Hibiscus the Same?

Yes and no. The name “Hibiscus” isn’t a common plant name, it is the genus that rose of Sharon (and other flowering plants) belongs to. They all have similar-looking tropical flowers, but there are some major differences. Rose of sharon, or althea, is a woody shrub that is hardy to cold climates. It grows in zones 5-9 and goes dormant in the winters, losing its leaves but not dying to the ground. Perennial hibiscus, also known as rose mallow, is a hardy perennial that dies to the ground each year but returns the following spring.

Side by side comparison rose of sharon and perennial hibiscus

Can Rose of Sharon Grow in Shade?

No, rose of Sharon cannot grow in the shade. It requires full sun (at least 6 hours direct sunlight) to grow and bloom to its full potential. If grown in shade, you can expect few to no blooms, weak stems, and droopy leaves.

Is Rose of Sharon Deer Resistant?

Yes, rose of Sharon is fairly deer resistant. Rutgers gives rose of Sharon a B-rating for deer resistance on their landscape plants rated by deer resistance list. This means that they are “seldom severely damaged”, but it is not impossible for hungry deer to take a few bites!

Is Rose of Sharon Toxic to Dogs?

According to the ASPCA, rose of Sharon is not toxic to dogs, cats, or horses. It is completely safe for your dog to play near, brush against, or even nibble on.

Written by: Miranda Niemiec, click here to read bio.

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