Golden rain trees (Koelreuteria paniculata) grow 1 to 2 feet per year to a mature height of 30 to 40 feet. These deciduous trees are also called pride of India, China trees, shrimp trees and varnish trees. The trees produce bright yellow flowers in summer or fall, followed by 1 1/2- to 3-inch seed pods that ripen in fall or early winter. Golden rain trees grow in U.S. Department of Agriculture plant hardiness zones 5 through 9. You can grow them from seed or take root cuttings from a well-established golden rain tree.
Soak seeds with hard seed coats in a bowl filled with warm water in fall. Soak them for at least 24 hours until the seeds swell. Nick very hard seed coats that do not swell after soaking for 48 hours with a sharp knife then soak them until they swell. Do not soak fresh, collected seeds.
Pour lightly moist coir, composted tree bark or sphagnum peat moss mixed with a handful of course builder’s sand, perlite or vermiculite into a small, zip-top clear plastic storage bag. Put the swollen or fresh seeds into the mix in the plastic bag and zip it closed. Store it in the refrigerator for three to four months.
Pour moistened seed germination mix, such as half sphagnum peat moss and half course builder’s sand, perlite or vermiculite into a seed flat or 3-inch-deep pots. Remove the seeds from the refrigerator. Plant the seeds at a depth equal to one to two times their width.
Put the seed containers in a bright area out of direct sunlight where room temperatures are 70 to 75 degrees Fahrenheit. Cover the container with a piece of plastic or put the container in a large, clear plastic bag and close the top. Moisten the seed mix if it begins to dry.
Remove the cover after the seeds germinate and you can see the tops of the seedlings. Continue to keep the seed mix moist. Pot them up separately with soil-based potting mix in 6-inch-deep pots when they are large enough to handle.
Root Cutting Propagation
Remove the soil from a small area of roots that are between 1/8 and 1/2 inch thick, using a shovel. Do this in fall, after the tree has dropped its leaves, or in winter or early spring, before the tree begins to grow new leaves.
Use sharp pruners to cut 2- to 7-inch-long sections of root, depending on the root thickness. Small, 1/8-inch-thick sections must be 7 inches long while 1/2-inch-thick roots can be only 2 inches long. Use sharp scissors to remove any small, fibrous roots growing along the length of the main root.
Pot the root sections in peat-based potting mix in containers with drain holes. Set them horizontally on top of the potting mix with multiple cuttings spaced 2 inches apart. Spread a 1/2-inch layer of potting mix over them and pour water gently over the potting mix to moisten it.
Set the containers in a cool area with temperatures between 55 and 65 F and bright but indirect sun exposure. Water them when the top of the potting mix begins to dry. Pot them up separately in soil-based potting mix when they sprout and develop a healthy root system.
Dig seedlings growing around an established golden rain tree in late winter or early spring before they begin to put on new leaves. Dig a 2-foot-wide, 1-foot-deep planting hole where the seedling will be planted.
Select a seedling between 6 inches and 2 feet tall. Push a shovel or sharp spade into the soil, 6 inches away from the seedling, making a circle all the way around it. Push a shovel into the soil 6 inches away from the seedling, under the roots and lift it up on the tip of the shovel.
Plant the seedling in its hole right away or keep the root ball moist until it can be replanted. Adjust the depth of the hole, if necessary, so the seedling will be planted at the same depth or slightly higher than it was growing before being dug.