There are many flowering trees in the springtime, less so in summer. The Chinese flame tree (Koelreuteria bipinnata) is a popular landscape tree for its summer-blooming long panicles of fragrant yellow flowers that turn into eye-catching papery orange, red, or salmon-colored seed capsules that look like Chinese lanterns. The canopy provides dappled shade, allowing shade-loving plants to be grown underneath.
This tree is best planted in the late spring after the threat of frost is over. The tree grows at a moderate rate, is quite tough, and can tolerate wind, air pollution, salt spray, heat, and drought. It has a deep, non-invasive root system so that you can plant it near a patio or a driveway. However, when selecting a location in your landscape, the tree spreads up to 35 feet.
|Common Name||Chinese flame tree, Bougainvillea golden rain tree, Chinese golden rain tree|
|Botanical Name||Koelreuteria bipinnata|
|Plant Type||Tree, deciduous|
|Mature Size||20-30 ft. tall, 25-35 ft. wide|
|Soil Type||Sandy, clay, loamy|
|Soil pH||Acidic, alkaline|
|Flower Color||Golden yellow|
|Hardiness Zones||7-9 (USDA)|
Chinese Flame Tree Care
Chinese flame tree can withstand challenging environmental conditions such as air pollution, drought, and a moderate amount of salt runoff, which is why it is often planted as street tree in urban areas or parking lots.
One drawback of the tree is its weak wood that breaks easily under mechanical impact. You should prune its lower limbs away from mowers and tractors. Also, remove horizontal limbs because they are susceptible to high wind.
The tree requires the most attention during its first couple of years until it is well-established. Because the Chinese flame tree has an irregular growth pattern, it is important to prune and train it to encourage a strong branch structure.
Chinese flame tree needs full sun, otherwise it becomes leggy and unsightly.
It is tolerant of a wide variety of soils but does best in well-drained soil.
Regular moderate watering is needed until the tree is well-established. Drench the soil around the tree until it's saturated up to 6 to 9 inches deep. Do not water again until the top 6 to 9 inches is dry. On average, ensure it gets 3 to 4 inches of water during the hottest months of June, July, and August. Provide between 2 and 3 inches in April, May, September, and October.
This tree takes about two to three years to become established. Once established, it is drought tolerant.
Temperature and Humidity
Chinese flame trees have good heat and humidity tolerance. They cannot withstand temperatures below 0 F.
After planting, add a complete slow-release fertilizer around the entire dripline of the tree to encourage the roots to grow outwards. The general guideline is 2 to 4 pounds per 1,000 square feet of the root area.
Established trees usually don’t need fertilizer other than a light annual application in the spring. It helps to keep the tree healthy and better resist disease.
Types of Chinese Flame Trees
In addition to the Chinese flame tree, other similar Koelreuteria species also flower in the summer and share many similar characteristics. The most significant difference is these other species are invasive:
- Golden rain tree (K. paniculata): Most commonly grown, cold tolerant down to 0 degrees Fahrenheit; native to central China
- Flame gold tree (K. elegans): Frost sensitive; native to Taiwan and Fiji
- K. formosa: A subspecies of K. elegans; no different from than flame gold tree
Chinese Flame Tree vs. Golden Rain Tree
The golden rain tree (Koelreuteria paniculata) was a popular specimen tree until it was classified as invasive in some parts of the United States because it easily reseeds itself. It's invasive in Kentucky, Virginia, Maryland, and Pennsylvania.
K. paniculata is hardy to zone 5, so it can tolerate colder winters than K. bipinnata. You can tell the two species apart by their leaves. Chinese flame trees have alternate bipinnately compound leaves, whereas golden rain trees have single pinnate, compound, feathery leaves. Both have yellow flowers, but the Chinese flame tree seed capsules are more colorful than the golden rain tree.
Chinese flame trees should only have one central trunk from which strong branches spread out with ample space between them, in other words, an airy canopy.
If extra trunks grow at the base, remove them and any branches that are close together. In a mature tree, continue removing any lower branches that can get in the way of traffic because the wood and the bark are easily damaged by mechanical impact.
Propagating a Chinese Flame Tree
A Chinese flame tree can be propagated from seeds or by root cuttings. They can propagate themselves from the seeds blowing over your yard, and you might find little flame trees starting to grow. But another way to propagate is by taking a root cutting. Here's how:
- Before you begin, you will need a shovel, sterilized pruning shears, a sizeable potting container, moistened potting soil, and sulfur powder. You will need to take a root cutting during the tree's dormant period from October to March.
- With a shovel, dig carefully to expose the roots in a small location by the tree.
- Locate a healthy root that is about 3/4 to one inch thick.
- With pruning shears, cut a 6-inch long section, then cut that section in half, keeping track of the part of the cutting that pointed toward the tree. (This is important as the cutting won't sprout if it is planted the wrong way.)
- Shovel the dirt back over the area where you took the root cutting, making sure to cover any exposed roots.
- Fill a large container with potting soil, and water the soil until moist.
- Dip the end of the cut root farthest from the tree into sulfur powder, and push that end into the soil.
- Put the container in full sun and water when needed. You should see shoots appear in approximately four weeks.
How to Grow Chinese Flame Tree From Seed
Chinese flame trees can propagate on their own from the seed pods that look like little Chinese lanterns. You can collect the seed pods, remove the seeds from pods, soak them or scarify them (knick them), and plant them in a container filled with potting soil and water it. Place the container in a bright, sunny spot. Keep the soil moist. The seeds will germinate in about eight days.
This tree can withstand most wintery weather after about its third growing season. Up until then, grow it in a temperature-controlled or sheltered environment, such as a greenhouse. The greenhouse doesn't need to be heated, but the young tree will benefit from the wind protection that a greenhouse provides. After its third year, you can plant it outdoors.
How to Get Chinese Flame Tree to Bloom
Summertime is when the Chinese flame tree blooms in a burst of long clusters of fragrant yellow flowers for several weeks. You do not have to deadhead this plant; only prune away dead branches and growth. Its golden flowers lead to the Chinese lantern seeds husks that are a flaming pink-orange-reddish sight to behold for three to five weeks.
It needs well-draining soil, a full sun location, and ample water to produce flowers and seeds. Make sure this tree gets more water in the hottest summer months. When fertilizing this tree, do not use nitrogen-heavy food. Nitrogen encourages foliage over flowers. Instead, choose a balanced fertilizer. Be patient; it can take a Chinese flame tree at least three years for the tree to mature and produce flowers.
Common Pests & Plant Diseases
Generally, the tree does not have common serious insect or disease problems. Old trees may develop root rot. Sometimes the bark gets canker. Cut out the affected branches and fertilize the tree the following spring. Fertilizing is also the only remedy if the tree gets verticillium wilt, a fungus that manifests by sudden wilting and browning of entire branches.
Common Problems With Chinese Flame Tree
Dead and Sunken Areas on the Bark
When this tree has a canker, you'll notice pink fruiting bodies developing on the tree's bark. To treat this condition, prune away the tree's infected branches and fertilize.
Wilting, Dying Leaves
Verticillium wilt can cause wilting and death of the leaves on the infected branches. This fungus can kill the tree and needs treatment immediately with fertilizer to stimulate new growth.
Tree Not Being Able to Handle the Cold
If your Chinese flame tree is having problems surviving in the cold, it could be that you are erroneously growing Koelreuteria elegans (USDA zone 9), a tree that is not as cold hardy as K. bipinnata (USDA zone 7). Ensure you have the right one before planting it.
How fast do Chinese flame trees grow in a year?
These trees can grow as much as two to three feet every year.
Are Chinese flame trees deciduous?
The Chinese flame tree is a deciduous tree and will lose its leaves every fall.
When does the Chinese flame tree yellow flowers bloom?
The Chinese flame tree shows its beautiful yellow flowers in the summer months of July through August.