How To Grow and Care For Japanese Zelkova Trees

The Japanese zelkova (Zelkova serrata) is a native of East Asia that has been in use in ornamental horticulture in the west since the 19^th century. It can provide a beautiful shady spot of dense ovate green leaves which evolve into a dazzling fall color show of purplish or reddish foliage. It has a wide vase shape, upright branching, and a noticeable curve of its tree trunk rather than growing straight. As the tree matures, the bark peels to expose orange patches. Plant a young zelkova in the springtime to avoid exposing it to frost. The tree will have a medium growth rate of 1 to 2 feet annually.

Japanese Zelkova Care

Although this is a versatile tree, be prepared to put in the maintenance, particularly when it comes to pruning. You will want to keep your Japanese zelkova from becoming damaged, especially in areas where there's a chance of icing, as this can cause more significant issues down the road.  

Light

The Japanese zelkova thrives in full sun to partial shade. The sunnier the location, the better the fall colors will be.

Soil

A very adaptable tree, the Japanese zelkova will tolerate clay, loam, and sand, providing the soil is well-draining. Soil pH is also not a significant concern. 

Water

One positive aspect of the Japanese zelkova, and a reason it makes a terrific street tree, is that it tolerates drought very well and does not need much supplemental watering after it has been planted.

To establish the tree, give it a good thorough soaking weekly for the first season to the point of ground saturation. Infrequent, deep saturation is better than quick and often when watering newly planted trees.

Temperature and Humidity

The Japanese zelkova is relatively cold hardy and can thrive in most temperate regions of the United States. The ideal USDA zones for the zelkova are 5 through 8.

Fertilizer

Japanese zelkovas require no regular supplemental fertilizer. If the tree is not performing well, it might be wise to amend the soil to provide a bit of a boost. Test your soil to establish the best type of amendments to handle any soil deficiencies that may be occurring. 

Types of Japanese Zelkova

There are several popular cultivars of Japanese zelkova meant to fit into smaller or larger spaces to accommodate the tree's spread.

• 'Halka': Fast-growing and large, used for commercial settings, such as parking lots and medians
• 'Village Green': Wide-spreading, needs plenty of room to grow, and is often used for commercial settings
• 'Wireless': Very wide, broad spread, and grows lower than other cultivars, but branching is higher on the trunk, making it a good shade tree in the yard
• 'Green Vase': Narrower vase-shape that doesn't need as much room for its spreading crown; makes a good driveway or street tree
• 'Musashino': This tree has an even narrower crown than 'Green Vase'
  

Pruning

The zelkova requires pruning to develop its structure, which will help avoid breakage. While in the nursery, it is essential to select a tree that has a single leader. The species will continue to grow branches that bunch and split inward towards the leader, creating deep “V-shaped” crotches. These branches need to be pruned yearly in the late fall through late winter to eliminate these extreme V-shapes.

Propagating Japanese Zelkova

Propagate a Japanese zelkova by seeds or plant cuttings. Seeds can produce variations of zelkova but cuttings taken from a specific tree will give you uniform seedlings if you prefer to propagate a group of similar zelkovas. Here's what to do when you take a cutting in the spring or early summer:

• With a sterile cutting tool, take a new branch that is 4 to 6 inches long.
• Remove the lower leaves but leave a couple on top of the cutting.
• Dip the bottom of the cutting into rooting hormone.
• Place the cutting into a pot with moist potting soil. If you are putting a few cuttings into one pot, space them about 1 inch apart.
• Expect cuttings to root in about 10 weeks. Repot to larger pots until they can be planted in a permanent spot.

How to Grow Japanese Zelkova From Seed

Growing this tree from seed can be achieved, but it requires a lot of patience. You will need to keep the seedling in a pot for a couple of years until it is strong enough to be planted outdoors in its permanent place. If you want to grow Japanese zelkova from seed, harvest the seeds in the fall when the tree's flowers have faded and the pods have dried. Take these steps:

1. Put seeds into a bag of moist sharp (or builder's) sand and refrigerate for six to eight weeks for a cold period that will break dormancy. Alternatively, you can keep them in a bag stored in a cold outdoor shed or outbuilding.
2. Then sow the seeds (and any that have already germinated) into pots filled with garden soil about 1/4 inch deep.
3. Keep the pots out of direct light and keep soil moistened.
4. Seeds should take a couple of months to germinate.

Common Pests & Plant Diseases

Zelkova trees are susceptible to aphids that will attack the tree in the spring. Aphids will cause leaf and twig damage and ultimately death. Scale insects are another issue for zelkovas. These insects suck the juices from leaves and twigs of the tree, leaving behind waste, called "honeydew."

The tree can experience Phytophthora stem and collar (the swollen area around the base of a branch and trunk) rot disease. This soil-borne organism forms cankers on the tree's twigs, but not on the leaves.

Common Problems With Japanese Zelkova

The primary concern that Japanese zelkova presents is how easily it breaks. A habit the species has is the tendency to grow multiple leaders while having very fragile wood. Having multiple leaders is a genetic weakness in the species that is somewhat solved in some available cultivars but not in the wild type. If searching for a Japanese zelkova, it is crucial to buy a tree with a single trunk or leader, or the tree will eventually experience breakage at the tree’s crotch later in its lifespan or if it experiences ice.