Koelreuteria

koelreuteria

( kole - roo - TEER - ee - uh )

At-A-Glance Information

This genus of small trees is native to southern and eastern Asia and includes species which produce loose clusters of yellow flowers followed by papery fruit capsules. They are commonly known as Chinese Lantern Tree or Golden Rain Tree and need full sun and moderate to regular water to perform well in the garden. Golden Rain Trees are great as patio, lawn, or street trees, and their flowers and capsules can be used in fresh and dried flower arrangements. In the garden, use them near patios, as shade trees, in rock gardens or dry creek beds, or near beehives where they can be frequented by pollinators.

koelreuteria Species and Varietals

The genus Koelreuteria includes just three species and is a member of the plant family Sapindaceae. It is related to Aesculus, Acer, and Litchi. The best growing zones for Koelreuteria trees vary depending on the species; for more information, see the descriptions below. To find your zone, click here: Zone Map.

Koelreuteria bipinnata (Chinese Flame Tree, Bougainvillea Golden-Rain Tree, Chinese Golden Rain Tree)
This species is native to southeastern China and northern Vietnam, and grows well in USDA hardiness zones 7a-10a or Sunset growing zones 8-24 and H1. They reach 20-40 feet tall and a little less wide. Leaves turn yellow for a brief time before dropping, and flowers are present in late summertime. Blooms are followed by long-lasting fruit capsules that take on shades of red, salmon or orange. These trees need pruning to develop a high-branching habit. Roots are deep and noninvasive, making them good street trees. This species is considered invasive in the southeastern and southern United States.

Koelreuteria elegans (Flamegold Rain Tree, Taiwanese Rain Tree, Golden Riain Tree, Bougainvillea Flame Tree)
These trees reach between 50 and 56 feet tall when mature, these deciduous trees are endemic to Taiwan and Fiji. It is widely used as a street tree in tropical and sub-tropical regions of the world, and produces pink to salmon-colored flowers. This species is considered highly invasive in warm climates, including Florida, Hawai'i, Texas, and Alabama in the United States and Australia.

Koelreuteria paniculata (Golden-Rain Tree, Varnish Tree, Pride of India, Panicled Goldenraintree, China Tree)
This species is best in USDA hardiness zones 5-9 or Sunset growing zones A2 and 2-24, and is the type species in the genus. Trees have an open branching structure, reaching 20-35 feet tall and giving light shade. New leaves are flushed purple, mature to green, and may or may not turn yellow in fall depending on the climate. These trees produce very showy flower clusters in summertime, and fruit capsules emerge red and age to brown. They trees tolerate cold, heat, drought, wind and air pollution well, making them perfect for harsh urban environments. Prune early on to prevent an awkward growth habit. This species is considered invasive in the Mid-Atlantic, Southeast, and Midwestern United States and regions of Western Europe. Commonly grown cultivars are listed and described below:

'Beachmaster'
Dense, broad canopy. Compact patio tree to under 10 feet tall at maturity.

'Coral Sun'
Coral new growth matures to green. Stems are coral. Does not flower.

'Fastigiata'
A columnar variety to 25 feet tall and 4-7 feet wide.

'Golden Candle'
Reaches 35 feet tall and 3-4 feet wide.

'Rose Lantern'
Seedpods are flushed with pink tones.

'September'
Blooms later in the year, more into fall than in the summertime. 20-30 feet tall.

'Sunleaf' ('Summerburst')
Dark green foliage, rose-pink capsules in fall. To 30 feet tall and wide.

'Variegata'
Slow-growing form with cream-green variegated foliage. 25-40 feet tall.

Caring for koelreuteria

Plant Golden Rain Trees in a spot in the landscape that receives full sun. For best performance (including foliage and flowering), ensure that the tree will be getting at least 6 hours of full sun each day. The more sun these trees receive, the more blooms will form. Although these trees are adaptable to wide variety of substrates, they do prefer well-draining soil that is acidic to neutral (with a pH of between 6.0 and 7.5). If soil is especially clayey or does not drain well, amend planting site with plenty of sand and organic material before installing trees. Apply a thick layer of mulch around the base of trees to increase soil moisture retention, suppress weed growth, and regulate soil temperatures. Water new plantings regularly to help them establish a strong root system. Mature trees are considered drought-tolerant, and can withstand periods of dry weather. However, when the climate is regularly hot or dry, ensure that trees are getting deep watered occasionally.

In springtime, apply a dressing of organic compost around the base of trees to supply the nutrients needed for the growing season. These trees are not heavy feeders, but if they seem to be struggling, they may benefit from a springtime application of a balanced (10-10-10), slow-release fertilizer to support the growth and flowering for the year. These trees have a beautiful naturally rounded canopy, and benefit most from light prunings. New plantings should be pruned for shape in their early years. Branches are upright growing, bend down somewhat as the tree grows, they might break due to poor collar formation, pruning is required to build a strong branching structure and a single stem and also for the pedestrian and vehicle clearance. These trees are characterized as weak-wooded trees. In late winter or early springtime, lightly shape trees and remove dead, damaged, diseased, or crossing branches to open up the canopy. Avoid heavy prunings, as this may damage the tree. They can live for between 50 and 150 years, and will self-seed freely; there will be no shortage of volunteer saplings to replant elsewhere or to share.

Propagation

Koelreuteria can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your tree, follow the instructions below:

Propagating Koelreuteria by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. A good substrate for propagation of cuttings is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
In late spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch softwood portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.

Propagating Koelreuteria by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
Harvest your seeds. Koelreuteria plants are contained inside of the small fruits produced in late summer and fall. The fruits are held in bunches at branch tips, where flowers once bloomed, and have papery coverings. Fruits are reddish or green when unripe, and mature to brown when they are ready for harvesting. Each fruit contains three round, black shiny seeds. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area until you are ready to work with them.
Koelreuteria seeds have a hard coating that protects them, but this coating also makes it a little difficult to get them to germinate. We can help the process along by scarifying them with sandpaper (or simply rubbing them against an abrasive surface). Do this with as many seeds as you can; they will probably not all sow, and the ones that do will be of varying characteristics. The more seeds you plant, the more chances you will have to get the resulting shrub you want. Place your seeds in lukewarm water for six hours. Viable seeds will sink to the bottom, and non-viable seeds will float to the top. You can discard any seeds that float.
Next, seeds will need to be cold-stratified in order for them to germinate. Place the seeds for three to 90 days in a fridge, stored in a plastic bag filled with moistened peat moss or sand. After this period of time has passed, remove the seeds from the peat moss and set them aside.
Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 7-14 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.

Koelreuteria trees are prized for their decorative papery seed coverings.

Each papery fruit contains up to three round, black seeds.

Problems and Pests

Certain species are considered invasive in some regions; see the species descriptions above for more information. Check with local authorities before planting. Koelreutieria trees can have issues with the following pests and diseases in the landscape