How to Grow and Care for Korean Fir

Like other fir trees, Korean fir (Abies koreana), is a short-needled evergreen conifer with the typical pyramidal growth habit that makes firs so popular as Christmas trees. But Korean fir can also be an excellent choice as a landscape tree since many varieties grow to no more than about 30 feet—much smaller than many other fir species. Korean firs have dense branches covered with short needles that are dark green on top with silvery undersides. They produce distinctive cones around 3 inches long, which start out purple and mature to a tan color. This evergreen tree is known for its fairly slow growth rate, especially in the early years. A small seedling might take 10 years to reach a 10-foot height, and some varieties will take as much as 50 years to reach their full size. Korean fir is best planted in the fall.

Korean Fir Care

Korean firs are generally very low-maintenance trees, especially after they are established in the landscape. The key is to start them off right, planting them in a spot that has good drainage and preferably rich, acidic soil. Also, make sure to take into account their mature size when determining their spacing in the landscape—15-foot spacing is recommended when planting multiple trees. Choose the location carefully, as transplanting can damage the roots and weaken or kill the tree.

Plan to keep new trees well-watered, especially in the summer, and feed them annually. You likely won't have to do much, if any, pruning on your tree unless there's an unhealthy portion you need to take off. Just inspect it periodically for any signs of distress.

Light

This tree grows best in full sun, meaning at least six hours of direct sunlight on most days. But it also will tolerate partial shade.

Soil

Korean fir trees prefer rich soil with good drainage; they struggle in dense clay soil. They also like an acidic soil pH. The tree can tolerate a neutral pH but won’t thrive in alkaline conditions.

Water

These trees prefer consistent moisture in the soil, but they struggle in soil that remains too wet and soggy. So water your tree whenever the soil begins to dry out, but make sure no water is pooling around the tree. A layer of mulch around the tree can be helpful to retain adequate soil moisture and keep the roots cool.

Temperature and Humidity

Although Korean firs tolerate heat and humidity better than many other fir species, they still prefer a cool, temperate climate. They also can handle some wind but should be sheltered from strong drying winds.

Fertilizer

Feed young Korean fir trees annually in the early spring before new growth picks up, using an organic granular fertilizer. Mature trees should be fed with a diluted half-strength fetilizer unless you have poor soil. 

Types of Korean Fir

There are several varieties of Korean fir trees, including:

• Abies koreana 'Aurea': This variety is commonly known as the golden Korean fir, thanks to its bright golden needles in the spring that turn light green by winter. 
• Abies koreana 'Compact Dwarf': This especially small variety only reaches around 5 feet tall and 3 feet wide.
• Abies koreana 'Silberlocke': The needles on this tree curl upward to expose more of their silver-white undersides.
• Abies koreana 'Kohout Hexe': This miniature variety grows only around a foot tall.
• Abies koreana 'Silver Show': This variety features very tightly curled needles that expose their silver undersides. 
• Abies koreana 'Prostrata: This variety is a low-growing, ground-hugging plant that is ideal as a woody groundcover plant.

Pruning

Korean fir trees don’t require much in the way of pruning. They typically form a symmetrical pyramid shape all on their own. However, you should prune off any dead, diseased, or broken branches as you spot them. And you can prune any unsightly branches as needed. But don’t cut back branches extensively and expect them to regrow. You’ll likely end up with some bare branch stubs where you cut. 

Propagating Korean Fir

In commercial trade, Korean firs are normally propagated by grafting branches onto a rootstock of a different species. While firs can be rooted from branch cuttings, it is a very slow process that isn't practical for commercial propagation. Grafting is not a process that most amateurs can do successfully, so the most practical approach is to propagate from seeds—a slow process but one that is relatively easy. Here's how:

1. In the fall, as the cones begin to dry and the scale separate, pick some large, ripe cones and place them in a dish in a warm location. As the drying continues, the small seeds inside the cone should dry and drop into the dish.
2. Stratify the seeds by soaking them overnight, then place them in a container filled with damp peat moss in the refrigerator for one to four months.
3. Plant the seeds at a shallow depth in small containers filled with a mixture of peat moss and perlite or vermiculite. Place them in a bright location at 60 to 70 degrees Fahrenheit and keep the growing medium damp until the seeds sprout.
4. After several weeks, when the seedlings begin to send out true needles, carefully transplant them into larger containers filled with garden soil and well-decomposed compost. Grow them in a sunny location through the spring and summer until well established. During this time, feed them twice a month with diluted organic fertilizer.
5. Your seedlings trees will be ready to plant in the landscape in the fall when they are 1 to 2 feet tall. In some cases, this may involve allowing the tree a full two years in the pot before it is transplanted into the landscape.
   

Potting and Repotting Korean Fir

Smaller cultivars of Korean fir can make excellent potted trees—they are especially popular as living Christmas trees.

Choose a large pot—at least twice the width and depth of the root ball of your tree. The larger the pot, the less frequently you will need to repot. As a growing medium, a mixture of 1 part perlite or vermiculite with 2 parts compost works well. Or, an ordinary commercial potting soil is fine. You may be able to grow this slow-growing species for four or five years in the same pot before it becomes root-bound and needs to be repotted.

Overwintering

Provided your climate zone is appropriate, fir trees planted in the landscape require little extra winter protection. Winter burn is less likely for this tree than for other conifers. But it's a good idea to make sure the tree is well watered in the weeks leading up to winter frost.

In colder regions, a potted tree will have its roots quite exposed to winter temperatures, so take precautions to place the tree in a sheltered location and to wrap the sides and bottom of the pot with insulating material, such as bubble wrap. Don't keep the potted tree on a paved surface, as stone or concrete surfaces will quickly conduct cold up to the tree's roots.

Some gardeners have good luck burying potted trees up to the top rim of the pot for the winter, or heaping dense compost around the pot to guard against temperature fluctuations.

Common Pests and Plant Diseases

These trees don’t have serious issues with pests or diseases, though they don't do well in areas with high air pollution. They can be susceptible to certain insects, including aphids and adelgids. If these insects are present, the tree’s needles might turn yellow or drop off. Forcefully spraying the needles with water to dislodge the insects every other day or so is a natural way to get rid of them. You also can apply insecticidal soap or horticultural oil, though this can discolor foliage. It’s important to remove and replace any mulch around your tree each spring to prevent any dormant insect pests from returning and infesting the tree.

A variety of fungal diseases are possible with Korean fir:

• Root rot can occur with trees that are planted in dense, wet soil. Once severe root rot sets in, your tree probably won't be salvageable.
• Needle rust begins with small white pustules on the lower surface of the needles, then causes the needles to turn yellow and fall off. Viewed from a distance, the tree will appear to gradually turn yellow. There is no effective treatment for fir needle rust, but because this fungus requires fern as a second host to complete its life cycle, removing ferns in the area often prevents the disease from returning.
• Twig blight causes branches to die back, beginning at the tips. Lower branches are usually affected first. Have the fungus diagnosed by a local arborist or university extension service, then apply the recommended fungicide. Keeping trees healthy will usually prevent this disease.

Common Problems With Korean Fir

In addition to the pest and disease issues common to this species, keep an eye out for these issues:

Needles Are Yellowish Rather than Green

If your tree seems to be more yellowish than is usual for Korean firs, it may be because the soil is too alkaline, which prevents the tree from properly absorbing soil nutrients. More frequent feeding with an acidifying fertilizer may help your tree, or you can try amending the soil with acidifying organic material, such as pine needles.

Branches Turn Brown in Spring

When the branches on your Korean pine turn brown in spring, at the very time you're expecting fresh green growth, it usually means your tree has experienced winter burn from cold, dry, winter winds. This often occurs if you live in a borderline zone—the northern part of zone 5 or northward. Young trees can sometimes be protected with a loose tent or shelter made from burlap, but this is an unattractive solution; the better solution is to opt for a species more reliable for your climate.