It’s the time of year when the hibiscuses are sporting their
huge blossoms of bright colors.
Hibiscus, also known as rose mallow and rose of Sharon, is an
herbaceous annual or perennial, a deciduous shrub or small tree. It’s in the
plantae kingdom, order of malvales and genus hibiscus. The species hibiscus
moscheutos is a cold-hardy cultivar. Hibiscus is used in teas, dried edibles
and can be candied for desserts or garnishes.
My first experience with hibiscus was years ago when I bought a
beautiful potted plant at Home Depot. I was amazed by the size of the flower.
Unfortunately, that was also when I believed places sold only plants that would
grow in New Hampshire – unless they were annuals. Needless to say, my hibiscus
didn’t last long. I was then told hibiscus are tropical plants.
After I moved to Bradford from the Seacoast, I’d periodically
drive by a house in Hillsborough in late August. She had rows of tall hibiscus
growing along the driveway and garden along the road. I knew she couldn’t be
digging them up to bring inside for the winter. There were too many. How was
she getting hibiscus to survive?
I got my answer after I’d moved to Hillsborough in 2015. The
following spring, I made a stop at Agway as I was creating more gardens. Agway
had hibiscus plants for sale! Melissa told me these were perennial hardy
hibiscus and would survive winters of zone 4 hardiness. I was excited and
throughout the next couple weeks, I bought four in different colors. (I loved
them so much I kept going back for more.)
I later learned that tropical hibiscus has single or double
blooms with green, glossy leaves. Hardy hibiscus has single blooms and
heart-shaped (what I call fingered) leaves of a duller green (the leaves on one
of mine are reddish).
What’s eye-catching about hibiscus is the size of the blossoms
and how tall they grow (up to 5 feet). Flowers can be 6 inches or more in
diameter (the bigger 10 to 12-inch blooms are called dinner plate hibiscus),
with colors ranging from yellow, peach, purple, shades of red and there’s now a
blue one called Bluebird Hardy Hibiscus. (Oh, I want one of these!) The flowers
attract butterflies and hummingbirds and bloom late July and August. The flowers
only last one or two days but more come.
Planting: Make sure your purchase is a hardy variety. Choose
a full-sun location with well-drained, rich soil. They
also do well near ditches and swamps. Dig a hole only as deep as the root ball
and two to three times as wide. Mix the soil removed from the hole with a small
amount of compost if the soil is in poor condition. Good soil doesn’t need to
be amended.
Carefully remove the plant from its pot and set it in the hole.
Fill the hole halfway with soil, then water well. Allow the water to settle which
eliminates air pockets. Fill the rest of the hole and water thoroughly. Add
mulch.
Care: Frequent watering is required in the first two months after
planting. Never let the soil dry out completely. Once established, water deeply
when the top few inches of soil feels dry. Hibiscus requires a large amount of
water while blooming; constantly moist, not wet. Water daily in warm weather
soaking completely through the root zone. However, cut back on watering once
the weather cools; too much water can kill it. Stake long stems if
needed.
Organic fertilizer with plenty of phosphorus encourages blooms.
Use a high potassium fertilizer in the summer, a diluted liquid
fertilizer one a week, a slow release fertilizer once a month or add a high
potassium compost to the soil. (As I often find, research can be
contradictory as one site said to feed twice a month during the growing season
– discover what works best for your plants.)
Check plants periodically for pests: aphids, white flies,
mealybugs and Japanese beetles. Control pests with a horticultural oil or
insecticidal soap. (I’ve purchased a variety of repellents along with Dawn dish
detergent which I’ve heard also works, but I’m afraid to use anything that
might harm bees and butterflies.) Also watch out for rust fungus, which also
affects hollyhocks and other mallow plants.
Pruning: Prune as necessary to control plant size. Cut back errant
branches to just above a side shoot. Cut the entire shrub up to
half its height after the first flush of blooms fade. This will encourage more
bud formation and maintain the size of the shrub. You can also just trim off
individual spent flowers to encourage further flowering. Keeping plants
deadheaded makes the gardens look tidy and prevents the seeds from sowing
unless seedlings are wanted.
If left alone, hardy hibiscus may self-sow and become weedy.
These seedlings will not necessarily be the same color as the parents. However,
they can be transplanted and moved throughout the garden.
Preparing for winter: Cut back dead stems to near ground level
in the fall after a frost. The stems usually die back to the
ground. Mulch over the root zone to provide protection and insulation for the
roots. The roots survive and the hibiscus quickly grows new stems in spring.
For the new season: Winter-damaged and dead stems may attract
pests or disease so prune off any dead stems in late winter/early spring. Hibiscus
is a slow growing plant often not showing signs of life until June, well after
other plants. Pinch the shoots of young plants in early summer to encourage
branching and more flower stalks to form.
Tip: They also do well in containers but do not transplant well.
It sounds like a lot of care, but it isn’t bad at all and the
rewards are worth it. The hardy hibiscus are such bright spots of color when
other summer flowers are starting to fade.
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