Posted by Brent Wilson on 8/7/2016 to Fertilizing & Watering Tips
When planted right and in the right spot Japanese holly shrubs are easy to grow and care for.
Japanese holly shrubs are used so extensively in landscape design because they come in a wide range of shapes and sizes that offer many uses in landscapes and gardens. Too, Japanese holly respond very will to pruning so can be sheared to various shapes and forms that provide visual interest in the landscape.
Japanese Holly shrubs are ideal for use as accents or in a straight or staggered patterns in home foundation plantings, in groupings or massed in landscape borders or on slopes, as low to mid-size natural or formal hedges (depending on the variety), and in containers or pots. If you're looking to create a theme garden, Japanese holly shrubs are perfect for use as clipped or sheared topiary specimens or hedges in formal gardens.
Here's a breakdown of what you need to know regarding planting and caring for Japanese hollies...
Japanese holly adapt to a wide variety of soil types provided the soil is well-drained. They prefer growing in a well-drained soil with average moisture. As with so many other types of ornamental plants, constantly soggy or wet soil can cause root rot and other harmful plant diseases. So make sure to plant them in a well-drained site!
How To Test Soil Drainage
If you are uncertain about soil drainage in the area you intend to plant, it's well worth taking the time to test the drainage before planting. To test soil drainage, dig a hole 12" wide by 12" deep in the planting area. Fill the hole with water and let it drain. Then, after it drains, fill it with water again, but this time clock how long it takes to drain. In well-drained soil the water level will go down at a rate of about 1 inch an hour. A faster rate, such as in loose, sandy soil, may signal potentially dry site conditions. A slower rate indicates poor draining soil and is a caution you need to improve drainage, plant in a raised mound or bed, or look for plants that are more tolerant of wet or boggy conditions.
Japanese holly perform and look their best in an acid to slightly acid soil ranging between 4.5 to 6.5 on the pH scale. Most average garden soils fall between a pH range of 6.0 to 7.0. If your soil is alkaline the leaves of your plants will turn a paler shade of green or even yellow.
How To Test Soil pH
Soil pH is a measurement of the alkalinity or acidity of soil and is measured on a scale of 1-14, with 7 as the neutral mark. Any measurement below 7 indicates acid soil conditions, and anything above 7 indicates alkaline. If you're unsure about the pH of your soil, and whether or not it's suitable for growing Japanese Holly, it's a good idea to test the soil pH in the planting area. You can quickly test soil pH with an inexpensive soil pH tester probe. To raise the pH (make more alkaline) you can add pelletized limestone to the soil. To lower the pH (make more acid) you can apply Soil Sulfur, Aluminum Sulfate, or Chelated Iron. Adding organic compost to the soil or using compost as mulch can also help to increase acidity and maintain acid soil conditions.
Learn More: What is Soil pH and How To Adjust It?
Japanese holly grow and look their best in full to mostly sun. Some light shade is tolerated. Too much shade and plants will become thin and weak looking. A minimum of 6 hours direct sunlight is recommended for best foliage density and foliage color.
Planting Japanese Holly In The Ground
Scroll down for container planting instructions and care tips
Start by digging your planting hole at least two to three times as wide and only as deep as the height of the rootball of your plant. The wider the hole the better. Place native soil removed from planting hole around the perimeter of the hole, in a wheel barrow, or on a tarp.
Depending on the type, fertility and porosity of the soil in the planting area you might need to mix in a soil amendment to the native soil removed from the planting hole. When planting Japanese hollies in dense clay or other poor draining soils it is beneficial to thoroughly mix in some good organic matter such as bagged top soil and/or a good planting mix at a 25-50% ratio with the soil removed from the planting hole. When planting in very sandy or quick-draining soil mixing in some top soil, peat moss and/or compost will help to retain moisture in the soil.
Remove your holly plant from the nursery pot. Firmly grasp the plant at its base and try to very gently remove it from the container. Be careful not to damage the plant when removing it from its pot. If the rootball is stuck in the pot cut the container away. After having removed the plant from the container, use your fingers or a claw tool to carefully loosen some feeder roots around the surface of the rootball.
If you are planting in well-drained soil, which is a must for Japanese hollies, set your plant in the planting hole so that the top edge of the rootball is at or just slightly above ground level to allow for settling. If your soil is moderately drained, meaning it drains slowly after rain, the top of the root ball should be 2 inches or more above ground level, as shown in illustration below. If necessary, add some backfill soil mixture to the bottom of the hole to achieve proper planting height.
Note: If the soil is poorly drained (constantly soggy or wet) take measures to improve drainage or select a different plant species tolerant of wet soils.
After setting your holly in the planting hole, use one hand to hold the plant straight and your other hand to begin back-filling your soil mixture around the root ball, tamping as you go to remove air pockets. When you have filled the hole to the halfway point you can soak the soil. Then continue back-filling to the top edge of the root ball. If you are planting the root ball higher than ground level, as shown in the illustration above, taper your soil mixture gradually from the top edge of the root ball to the ground level. To avoid suffocating your plant, avoid placing any soil on top of the root ball.
Step 6 (Optional)
When planting your Japanese holly in a site far away from a water source in well-drained soil, you can use remaining soil mixture to build a water retaining berm (catch basin / doughnut) that is 2 to 3 inches high or so around the outside perimeter of the planting hole. This basin will help to collect water from rainfall and irrigation, which helps to reduce the need for hand-watering. The berm can be removed after a year or so.
Next, deeply water the planting area, including the root ball, to a depth equal to the height of the root ball. For an extra boost, you can water your newly planted holly with a solution of Root Stimulator, which stimulates early root formation and stronger root development, reduces plant shock, and promotes greener, more vigorous plants.
To conserve moisture and suppress weed growth, apply a 1 to 2" layer of cured, shredded or chipped wood mulch or pine straw around the planting area. Avoid using freshly chipped wood for mulch until it has cured in a pile for at least 6 months, a year is better. Avoid placing or piling mulch directly against the base of your plant as this could cause the bark to rot.
Planting Japanese Holly In A Container
Japanese hollies growing in pots appreciate a moist, but well-drained soil. Constantly soggy soil can and often will cause root rot or other harmful or deadly plant diseases. Therefore, to ensure good drainage, use a pot with a drainage hole(s) and a quality potting soil or potting mix, or a 50/50 combination thereof, for planting. Optionally, you can also add some pumice or perlite (maybe 10 to 20%) to the soil mixture to help with drainage.
Choose a container with a drainage hole(s) at the bottom and one that is large enough to allow for 2 to 3 years of growth before shifting up to a larger size container. This might mean your planting pot would be 8 inches or more in diameter (width) than the root ball of your plant.
Container color will matter as well. Not only will you want to pick a color of container that goes well with the foliage color of your Japanese holly, you'll also want to pick a container that matches the style of your home or other structures and other plants in the surrounding environment.
Many nursery & garden centers offer a wide variety of containers to choose from. Before heading out to buy a container take pictures of your home and the surrounding environment. Doing so will help you to choose just the right color and style.
Container Planting Instructions
Before filling your container with the soil mix, I recommend lining the bottom with shade cloth or a porous landscape fabric. This will keep the drain holes from becoming clogged with roots and soil. If you use gravel or rocks in the bottom of the container lay the fabric on top of it.
Remove your holly plant from the nursery pot. Firmly grasp the plant at its base and try to very gently remove it from the container. Be careful not to damage the plant when removing it from the pot! If the rootball is stuck cut the container away. After having removed the plant from the container, use your fingers or a claw tool to carefully loosen some feeder roots around the surface of the rootball.
Pour a small amount of your soil mixture in the bottom of the container. Set your plant in the container and make necessary adjustments by adding or removing some soil so that the top edge of the root ball will sit approximately 1" below the rim of the container.
Backfill with your soil mixture around the root ball, tamping as you go, until the level of potting soil is even with the top edge of root ball.
Water thoroughly until water starts to drain from the holes in the bottom of the container. Add more soil mixture if settling occurs during watering.
Step 6 (Optional)
Apply a 1/2" layer of wood chips or sphagnum moss to soil surface to help conserve moisture. Stone mulch can also be used.
Japanese Holly Care Tips
Japanese hollies are very easy to care for and maintain. Below are some helpful care tips that will have you growing them like the pros.
How To Fertilize Japanese Hollies
To maintain good health and appearance, Japanese hollies will appreciate fertilization.
When To Fertilize?
Feed Japanese hollies in late winter or early spring before new growth begins to emerge and again in late summer.
What Type Of Fertilizer & How Much?
Fertilize Japanese hollies at rates recommended on the product label with a slow-release shrub & tree type fertilizer that contains iron and/or sulfur for deep greening. Alternatively, you can feed plants with an organic plant food. If plants look like they could use a second fertilization, you can feed them again in mid to late summer. To avoid frost damage to new growth stimulated by fertilization, cease feeding Japanese hollies two months prior to the first frost date in your area.
Note: If the foliage of your Japanese hollies develop chlorosis (leaves turn light green or yellowish) this could be an indicator of a high soil pH (alkaline soil). Japanese hollies prefer a low soil pH (acidic soil). First check the undersides of the leaves for chlorophyll-sucking insects. If no insects are present, simply apply iron or soil sulfur at rates suggested on the product label for deep greening of foliage.
Learn More: What is Soil pH and How To Adjust It?
Learn More: What is Soil pH and How To Adjust It?
How To Apply Fertilizer?
Shrubs feed themselves from their root system. The feeder roots of established shrubs are found at and beyond the outside perimeter of the branch system, what many professionals call the "drip line." Therefore, this is where most of the fertilizer should be spread.
How far outside the drip line you spread fertilizer will depend on the age and size of the shrub. As a general rule, spread the fertilizer 3-4 inches beyond the drip line for each 12-inches of shrub height. For example, if a shrub is two feet tall spread the fertilizer about 6 to 8 inches beyond the drip line.
Feeding Japanese Holly In Pots
Feed Japanese holly growing in pots and other containers as directed on the product label with a slow-release or water-soluble plant food listed for use in containers.
How To Water Japanese Holly
At Planting Time
Immediately after planting deep soak the soil in the planting area to a depth equal to the height of the plants root ball. For an extra boost, to stimulate early root formation and stronger root development, you can also water you newly planted Japanese hollies with a solution of Root Stimulator, which reduces transplant shock and promotes greener, more vigorous plants. When planted during the winter dormant season plants will require less water. So, be extra careful not to overwater during winter!
During the First Growing Season
In average garden soil you should not have to water your newly planted Japanese hollies every day. More often than not, this causes soggy soil conditions that can lead to root rot and other harmful plant diseases. In the absence of sufficient rainfall, water only as needed to keep the rootball and surrounding soil damp to moist. Keep in mind that deep soaking less frequently, and allowing the soil to dry out somewhat before watering again, is much better than splashing just a little water on the plants every day. Shrubs planted during the winter dormant season, when plants are not actively growing and evaporation is much slower, will require much less water. So, be extra careful not to overwater during winter!
When established Japanese hollies are fairly drought tolerant. That said, during prolonged periods of drought they will may require supplemental irrigation. If during a drought you see leaves wilting or falling from the plant, or new branch tips are drooping, this could be a sign your plants need a good deep soaking.
Note: When watering with an automated irrigation system it's best to set your timer to water during the early morning hours and not in the late evening or at night, which can lead to the onset of fungus and other foliage diseases. During the first few weeks after planting, check soil moisture often and adjust irrigation time if necessary to keep the soil moist, not wet.
How To Prune Japanese Holly
Japanese hollies do not require pruning but respond very well to it. They can be pruned or sheared regularly to maintain a formal shape or hedge, which they are immensely popular for.
When To Prune
Japanese hollies can be lightly pruned or sheared almost any time of year. Hard pruning, to rejuvenate an old and tired plant or to reduce the size of a plant that has outgrown the space it was intended to fill, should be performed in late winter before new spring growth begins to emerge. More on that below.
Note: To avoid freeze damage to tender new growth stimulated by pruning, cease pruning or shearing in fall two months prior to the average first-frost date in your area. When plants have stopped growing in winter pruning can resume.
How To Prune
Stray Branch Pruning
Any time of year, hand pruners can be used to cut back a stray branch that is spoiling the shape of the plant. Make your pruning cut at a point along the branch just above the main form of the plant. Removal of dead or damaged branches can and should be done when they appear. Cut damaged branches at a point just past the breakage. Cut dead branches off below the dead part or at their origin. Discard these plant parts.
Formal Hedges & Shapes
As mentioned, Japanese hollies are immensely popular for use as formal hedges or topiary shapes. Sharp hedge clippers or trimmers can be used several times during the growing season to lightly shear plants to desired shape. Cease pruning two months prior to the average first-frost date in your area. Pruning can resume in winter when plants have stopped growing.
Japanese Holly Topiary
If you have an old and tired Japanese holly that is thin and weak looking, or that has overgrown the space it was intended to fill, hard or rejuvenation pruning may be in order. This type of pruning is performed in late winter, when the plant is dormant and before new spring growth begins to emerge..
Rejuvenation pruning is a drastic form of pruning in which the entire shrub is cut back to a height of 6 to 12 inches above the ground. After cutting back a healthy shrub it will usually start growing new branches and foliage in spring.
Note: While Japanese hollies typically respond well to rejuvenation pruning there are no guarantees your plants will survive it. That said, if your plants are dying from disease or old age what do you have to lose? Even sickly plants sometimes are rejuvenated by this drastic type of pruning.
Plant Long & Prosper!
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