Garden Detective

Garden Detective: Will jacaranda bounce back from freeze?

I purchased a Jacaranda mimosifolia from a local nursery. I see these trees throughout Southern California and I love the beautiful blue blossoms. I realize my climate in Elk Grove is not ideal for these trees, but that’s what makes them unusual in our area. I am aware that they are sensitive to cold and, the first year I had this tree, I kept it in a container in my home. The second summer, I planted it in my front yard. I have been told that I might try wrapping Christmas lights around the tree during the winter to help my little sapling endure. In March, I looked at it and it is still clearly alive, but not a leaf or a blossom is on it. How long should I give it before I give up? Many other trees are beginning to bloom already.

– Don Price, Elk Grove

According to UC master gardener Carol Hunter, the Jacaranda mimosifolia is a sub-tropical tree that can withstand brief periods of temperatures slightly below freezing, once established.

Generally, this tree performs best in full sun although it can tolerate partial shade. It needs well-drained soil. In tropical regions, it is a versatile patio specimen or shade tree. When planted in the ground, it should have a sheltered location.

Even if the plant appears to have been damaged by cold winter temperatures in our area, it is likely to recover. Many people in the Sacramento area use Christmas lights to provide a little warmth to their tender plants during periods of frost. If you give this a try, you will need to use the old-fashioned bulbs that emit some heat.

Jacarandas are recommended for USDA Zones 9 to 11; Elk Grove is Zone 9B, so you’re right on the edge of a jacaranda’s comfort zone. Young jacarandas can take temperatures down to 26 degrees F. for a few hours, although they may sustain some damage. The cold exposure also may stunt or slow their growth; that may be what your tree experienced with its slow budding. Mature jacarandas can survive down to 20 degrees, but exposure to such freezing temperatures may keep them from blooming the next season.

I read in your column about the tulip myrtle infested with aphids. I have had the same problem. A few years back, I used your recommendation to use the Bayer’s Tree and Shrub Insect Control. I was not home at the time and a friend dosed my tree with the Bayer. The really sad thing was this tree was also covered with what appeared to be prehistoric-looking bugs. They were black and yellow – tiny lady bug larvae. Every last lady bug died and none became full-fledged winged creatures that would attack the aphids. So I have stopped using this pesticide. This year, when I started seeing aphids, I used water at first. Then, I sprayed my roses with Essential Lemon Oil in water; I only had to spray once and the aphid problem was gone.

– Kacy Curran, Granite Bay

It is unclear as to whether your friend applied the Bayer’s Tree & Shrub Insect Control as a spray or as a drench. When applied as a drench, the insecticide enters the soil where it is picked up by the plant’s roots and translocated into the stems and leaves, said UC master gardener June Bleile. The leaves are then toxic to plant-eating or sucking insects. A spray would be effective as long as it was on the surface of the leaf and not washed off by rain, sprinklers, or heavy dew.

The larval stage of lady beetles eat aphids. Because the aphids pierced the foliage, the transfer of chemicals to the larva is a possibility. As you noted, multiple daily sprayings with water is quite effective in controlling aphids. Chemicals should be used only as a last resort, and only as directed on the container’s label.