Japanese Holly Care.
Evergreen in appearance, the shrub known as Japanese holly (Ilex crenata) has a densely branched structure and a slow to moderate pace of growth. Many gardeners take pleasure in shaping it into topiaries, using it as a luxuriant hedge or border, or both.
The leaves of the shrub are typically spherical, glossy, and have a dark green color and their length ranges from just over an inch to just under two centimeters.
Late in the spring, it develops dainty blooms with four white petals that have a tendency to entice bees as well as other types of pollinators. The blooms are followed by spherical, dark-colored fruits that are quite tiny. Either autumn or spring is a good time to grow the shrub.
Care of the Japanese Holly
As long as you get it off to a good start, Japanese holly is a plant that requires just a moderate amount of upkeep. It is essential to put it in a location that has enough drainage in the soil and offers some degree of shelter from the weather, particularly blustery winds.
When it has reached maturity, the shrub normally requires watering only during extended periods of dry weather and feeding once per year. However, the addition of compost and mulch may be beneficial to the plant.
Unless you want to train the plant into a certain form, such as a curved topiary, it does not need a significant amount of trimming on a regular basis.
WARNING
The Japanese holly plant is regarded as an invasive species in some regions of the United States4 due to the fact that it has the ability to evade cultivation and take over the understory of woods.
Holly from Japan is poisonous to human beings
, canines, and feline friends.
In certain regions, it is regarded as an invasive species.
Light
The ideal growing conditions for Japanese holly are full sun to moderate shade. If you live in a warmer region, it will be grateful for some shade to protect it from the hot afternoon heat.
On the other hand, for it to flourish to its maximum potential in colder climes, it has to get either full sun or at least six hours of direct sunshine on most days. If there is not enough light, the plant will develop more slowly and its branches will be less thick.
Soil
This shrub is able to thrive in a wide range of soil types, including sandy soil, rocky soil, and even clay soil. Planting it in soil that is sandy, loose, and well-drained is the best way to ensure its success. It grows best on soil with a pH that is just barely acidic.
Water
The ideal quantity of soil moisture for Japanese holly plants is somewhere in the middle. To facilitate the establishment of the young shrubs’ root systems, the soil around them should be kept uniformly wet but not soaked. Shrubs that have reached maturity have some resistance to drought, and they can also withstand brief periods of floods.
However, being in soil that is excessively damp for an extended period of time may cause the plant’s leaves to develop a light green color and, eventually, cause the roots to rot and cause the plant’s death.
If you can put your finger into the soil and it feels dry a couple of inches deep, then it is time to water the plants. Add a layer of mulch that is two to four inches thick all the way around the shrub. This will assist to retain appropriate soil moisture and will keep the roots cool.
Temperature as well as Relative Humidity
The Japanese holly does not do well in either very hot or extremely cold climates and performs best in more moderate environments. It is in your best interest to put your shrub in a location where it will be shielded from strong winds throughout the winter, since these gusts may cause harm to the plant’s leaves.
The shrub also has the propensity to struggle in regions that have excessive humidity and instead favor locations with humidity levels that are more typical.
Fertilizer
In the spring, when new growth first appears, apply a fertilizer with a gradual release. In addition, it may be useful for the healthy development of the Japanese holly shrub to include some compost into the soil that surrounds the plant.
Different Varieties of Japanese Holly
There are several different types of holly native to Japan, including but not limited to:
The Ilex crenata ‘Dwarf Pagoda’ cultivar is a dwarf variety that only grows to a height of around two feet tall and has a growth habit that is very compact and dense.
Variegated foliage is a characteristic of the Ilex crenata ‘Golden Gem’ cultivar.
The Ilex crenata ‘Convexa’ tree grows to a height of around five to six feet and is well-known for the large amount of black fruit it bears.
The dwarf variant known as Ilex crenata ‘Helleri’ grows to a height of around two to four feet and a width of approximately three to five feet as it matures.
Ilex crenata ‘Lemon Gem’ is a dwarf cultivar that seldom grows higher than three feet and has yellowish leaf in the spring that transforms into lime green as the plant develops. It is often known as the ‘Lemon Gem’.
This cultivar of Ilex crenata, known as “Sky Pencil,” is an excellent option for use as a living fence due to its columnar form, which is slender, as well as its height, which ranges from six to eight feet.
Pruning
It is not necessary to prune Japanese holly plants very often. However, they may be pruned as often as is required in order to keep the appropriate form. In general, they are able to tolerate modest pruning at any time from the beginning of spring to the beginning of early autumn; however, any significant pruning should be undertaken in the early spring before new growth begins.
Pruning should be avoided around two months before the first frost that is expected to occur in the autumn. Pruning might foster fragile new growth that the frost will destroy if it occurs. As you find branches that are sick, damaged, or dead, remove them immediately.
You will need to do some minor pruning on your Japanese holly many times during the growing season in order to shape it into a hedge or topiary.
Do not attempt to give it the form you want all at once by harshly pruning it. If, on the other hand, you have an older shrub that has become overgrown and needs to be regenerated, you should prune it in the late winter so that it is around six to twelve inches above the ground.
This will result in the shrub being reshaped and healthy new branches being encouraged to sprout.
Propagating Japanese Holly
It is possible to grow Japanese holly from hardwood cuttings during the season when the plant is dormant:
use a knife or pruners that are very sharp. Remove a cane by cutting it just above one of the bud unions (the small bumps where the leaf meets the stem).
Then, remove about three-quarters of an inch of the cutting that is located above another bud union so that the final length of the cutting is approximately six inches. Take off all of the leaves except for the top two pairs.
The rooting hormone should be applied at the bottom end of the cutting.
Prepare a position in which the shrub will be exposed to the essential amount of sun, whether it be full or partial. Incorporate coarse sand into the ground, and then plant the cutting so that it is approximately one inch underground.
If there is no chance of rain or snow, you will need to periodically water the cutting in order to keep it wet.
It is expected that the cutting will start producing new growth in the spring, which is a sign that it has successfully rooted. You may either let it to continue growing in the same spot or transfer it to another site that is more suited.
Starting from seed to cultivating Japanese Holly
The majority of Japanese hollies used in landscaping are cultivars, meaning that their seeds will not yield a plant that is genetically identical to the species from which they originated.
Additionally, the process of the seeds growing might be unpredictable and take several years, even under optimal circumstances. As a result, growing Japanese holly from seed is not something that is suggested.
Planting and Replanting in Pots
Growing Japanese hollies in containers is an option for those who like dwarf types. Choose a container that is at least eight inches wider than the root ball of the plant. This will provide the shrub space to expand over the course of the following two to three years before you need to upgrade to a larger container.
Terracotta is an excellent material for containers since it allows excess moisture to escape and it is substantial enough that it will not collapse over easily. Put in some potting soil that drains well, and check to see that the container has enough of holes in it for excess water to escape.
Overwintering
When grown in an appropriate area that is protected from harsh winds, Japanese hollies are winter hardy up to USDA zone 5 and, in most cases, do not need any kind of winter protection.
However, they are better protected from the freezing and thawing cycle when several inches of mulch are spread over the plant’s roots. It is important that the mulch be distributed across an area that is at least as large as the reach of the branches.
Because Japanese hollies grown in pots are sensitive to having their roots damaged by the winter cold, it is important to winterize the plants by placing an insulating silo around them.
Pests and diseases that are often seen on plants
The holly leaf miner is an insect that feeds on Japanese holly and causes damage to the plant by sucking fluids out of the leaves in the late spring. Scale insects, whiteflies, and spider mites are three other types of pests.
Nematodes, root rot, and stem cankers are the three most frequent plant diseases that can cause damage to the plant. Root rot is another prevalent plant disease.
How to Achieve Flowering with Japanese Holly
It might take between two and three years for the Japanese holly to produce its first blossom after being planted. If you have propagated it from a cutting and it hasn’t bloomed yet, it’s possible that it’s still too young.
Problems Typically Encountered with Japanese Holly
The leaves often turn yellow for no apparent reason. Even if there could be enough iron in the soil, this is often a warning that the soil is excessively alkaline, which leads to iron deficiency in the plant.
However, there might be enough iron in the soil. It is necessary for the soil to have a tiny acidity in order for hollies to be able to absorb iron. To correct this, you should apply an acid-loving tree and shrub fertilizer to the plant and follow the recommendations on the package.
FAQ
Should I make sure to plant both a male and female Japanese holly?
Because it is a dioecious plant, Japanese holly requires two separate plants in order to produce fruit: a male and a female. It is important to take note that the shrub won’t start producing berries until it is at least six to eight years old on average.
Is there a difference between boxwood and Japanese holly?
Even while it has a similar appearance to boxwoods, which is how it got its other popular name, box-leaved holly, this holly belongs to a separate species.
How quickly does a Japanese holly mature into an adult?
It grows anywhere from six to twelve inches each year, which classifies it as slow to medium growth depending on the cultivar.
