Nature is great at adapting, but sometimes a little human ingenuity is needed to take an already great plant and make it better. Kleim’s Hardy Gardenia is one example.
The Gardenia jasminoides (gar-DEEN-ya jaz-min-OY-deez), or cape jasmine, are often considered the most beautiful gardenia species. Cape jasmine hails from Japan and southern China.
This highly-prized plant prized with its roselike blooms, great fragrance, and relatively easy care still has problems.
And then the cultivar ‘Kleim’s Hardy’ came along.
Kleim’s Hardy gardenias outperform many treasured members of the Rubiaceae family.
They handle cold and sunlight better than their parent plant while also being a compact dwarf variety, meaning it’s even easier to grow indoors.
While best known as simply Kleim’s Hardy gardenia, this perennial sport also sometimes goes by:
- Cape Jasmine ‘Kleim’s Hardy’
- Cape Jessamine ‘Kleim’s Hardy’
- Kleim’s Hardy Cape Jasmine
Kleim’s Hardy Gardenia Care
Size & Growth
As a dwarf cultivar, Kleim’s Hardy reaches a rounded, compact adult size of only 2′ to 3’ feet around.
It’s a relatively slow grower with evergreen foliage.
The leaves are lanceolate and glossy, dark emerald green, appearing in opposite, whorled pairs.
Flowering and Fragrance
In late spring, the green leaves will be augmented by showy, effervescent blooms.
The 2” inch white flowers have 5 to 7 petals in a star shape with a golden stamen.
As the blooms die, they give way to small 1 to 3” oblong orange berries, which attract songbirds.
Details: Gardenia Blooming Times
Light & Temperature
One of this cultivar’s claims to fame is its higher tolerance of sunlight, handling direct sunlight for much of the day without scorching.
A spot in the garden with 6 to 8 hours of direct sun in the morning and light afternoon partial shade is best.
You can give it 2 to 6 hours of direct sun in cooler climates, even in the afternoon, and it will be fine.
Indoors, there’s no need to protect the plant from a sunny window unless it’s especially bright and hot out and the window’s closed.
As with all gardenias, your cape jasmine ‘Kleim’s Hardy’ requires higher humidity.
Place it in a sunny kitchen window or provide it with a pebble tray or humidifier.
Misting is fine, but make sure you don’t do it when the plant’s in direct sunlight, as this will cause the water droplets to scorch the plant as they evaporate.
This plant is more cold-hardy than any other gardenia currently on the market.
It can thrive outdoors in USDA hardiness zones 7a to 11a.
As with its parent plant, daytime temperatures of 68 to 74° degrees Fahrenheit are perfect.
However, it prefers nights to be a little under 60° degrees Fahrenheit to produce the best blooms.
‘Kleim’s Hardy’ is known to be cold hardy down to 0° degrees Fahrenheit and will even survive in zone 6 if adequate mulching is provided.
Watering and Feeding
Using the ever-trusty finger test, check the soil and water thoroughly when the soil has dried 1” inch down.
Only use room temperature distilled water or rainwater to avoid harmful chemicals.
This cultivar will enjoy a good azalea fertilizer or other plant food with a 2-1-1 NPK ratio in spring.
Around 6 weeks later, give it another feeding to encourage blooms.
The plant may also need iron supplements or an acid fertilizer after blooming to help restore soil quality if you’re between repottings.
Related: Gardenia Fertilizing Tips
Soil & Transplanting
If there’s one thing a rich plant like Kleim’s Hardy deserves, it’s a rich home.
Treat it to acidic soil with a pH of <6 to avoid chlorosis (i.e., leaf yellowing).
The soil should be well-draining and contain plenty of organic matter.
Clay, loamy, or sandy soils are fine if they are amended with organic materials and/or aggregate.
A good option is to use an azalea, or gardenia potting mix mixes with equal parts aggregate (coarse sand, perlite, or pebbles for drainage) and organic matter (coco coir and peat work best.
You may also choose to do 2 parts soil and 1 part aggregate when planting outdoors, using organic mulch as a component.
1 to 2” inches of mulch is essential for healthy growth outdoors.
The mulch protects your gardenia’s roots from heat, cold, and frost while degrading into nutrient-rich organic matter.
This also helps prevent the soil from drying out too quickly in heat waves and defends the plant from weeds.
As this is often grown as a container plant, you may find it impossible to avoid repotting.
Do so once every two years using fresh soil and allow it to recover, as gardenias are notoriously sensitive to transplant shock.
Grooming And Maintenance
Prune straggly branches after blooms are finished and before the first frost to improve its hardiness.
You may also deadhead if desired.
Propagating Kleim’s Hardy Gardenia
Both seeds and stem cuttings easily propagate this cultivar.
Cape Jasmine ‘Kleim’s Hardy’ Pests or Diseases
This plant is cold hardy down to 0° degrees Fahrenheit and is deer resistant.
Aphids, mealybugs, scale, spider mites, and whiteflies are all common infestation risks. Use Insecticidal soap or Neem oil for control.
Likewise, the plant is known to be susceptible to Anthracnose, leaf spot, powdery mildew, and sooty mold.
As with other gardenias, it is non-toxic to humans and mildly toxic to pets (may cause diarrhea, hives, or vomiting, but is not life-threatening).
Related: Gardenia Leaves Turning Brown
Gardenia jasminoides ‘Kleim’s Hardy’ Uses
This gardenia sport is nice and compact, perfect for containers, borders, and raised beds.
It also finds use as a low hedge and in a variety of garden settings.
As they are non-toxic to children, they make a good addition to outdoor play areas.
Kleim’s Hardy has a wonderfully heady scent that attracts pollinators and is perfect for entryways and patios.
Conversely, keep them near windows so the scent can migrate in, and you can enjoy the songbirds once it fruits.