Most identifiable by its dripping clusters of yellow flowers, the golden chain tree (Laburnum spp) makes an attractive and showy focal point in the landscape. For all of its beauty, this deciduous tree comes with serious risks. This poisonous tree may cause irritation and allergic reactions in some individuals, and produces toxic sap from pruning cuts. The golden chain tree grows in U.S. Department of Agriculture plant hardiness zones 5b through 7b, and requires yearly pruning to maintain its health and form. Prune this tree just after it finishes blooming in the early to mid-summer while its sap flow remains slow.
Pour 1 part bleach and 4 parts water into a bowl or other container. Submerge the blades of pruning shears, loppers and a pruning saw into the bleach solution for 5 minutes to kill any clinging diseases or pathogens. Let the tools air dry before making any cuts.
Put on a long-sleeved shirt and a pair of gloves to prevent your arms and hands from coming in direct contact with the poisonous golden chain tree in order to avoid injury, irritation or an allergic reaction. Do not directly touch the tree while devoid of this protective clothing.
Cut out any dead branches in the tree's canopy. Use pruning shears to cut limbs with diameters of 1/4 inch or less, loppers for diameters of 1 1/2 inches or less, and a pruning saw for diameters greater than 1 1/2 inches. Make each cut 1/4 inch above the branch bark collar, the swollen ring surrounding the branch's base.
Trim away any broken branches, cutting them back to healthy wood located below the damaged portion. Position each cut 1/4 inch above an outward-facing lateral branch, leaf stem or branch base. Remove all diseased branches completely, sterilizing the pruning shears in the bleach solution after each cut.
Remove any limbs growing at an angle less than 45 degrees in relation to the trunk, cutting them 1/4 inch above the branch bark collar. Cut out any branches that cross or rub against another.
Prune back all suckers, or thin vertical new shoots, growing from the tree's trunk or base. Cut them as close to their bases as possible without damaging or cutting into the tree's trunk. Thin the canopy by removing any watersprouts, vertical young shoots, growing in the tree's canopy.
Remove any lower branches that impede nearby foot traffic. Shape the tree lightly by cutting vigorous, overly long or straggly branches back by one-third their length. Position each of these cuts 1/4 inch above a leaf, growth node or lateral branch.
Remove all of the spent flowers and developing poisonous seed pods. Cut each flower or pod off at the base, as close to the branch as possible without cutting into the wood.
Gather the removed stems, dead flowers, seed pods and leaves. Deposit this plant material into a trash bin, cutting the larger branches up into smaller pieces if needed. Disinfect the pruning tools in the same manner as before to remove any diseases or clinging sap.