April Q & A
by Michelle Le Strange, UC Master Gardener Advisor

Q. Every year I purchase Easter lilies for the holiday. Can I plant them in my garden when they have finished blooming?

A. Yes, you can transplant your lilies outdoors, just be sure that the soil has good drainage. Space the plants 12-18 inches apart and mulch deeply since lilies like their feet in the shade and their heads in the sun. As the leaves and stems of the original shoots die, prune them off. New growth will soon emerge, sometimes producing a second round of flowering. In the fall, the lily stalks will turn yellow and dry. Next spring, carefully pull back the mulch to allow the new shoots to emerge, and apply a balanced fertilizer.

The Easter lily you purchased was forced to bloom in April. In your garden it will revert to its natural bloom time, flowering in August or September.

Q. I just moved into an older home with an established garden. There are several heavenly bamboo (Nandina domestica) plants that haven't been pruned in years, which are now top-heavy and bare at the base. Do you have any tips on how to prune these bushes so they are more attractive?

A. Heavenly bamboo is one of the most common plants and also one of the most overlooked for providing elegant grace in the landscape. Homeowners and commercial gardeners alike often totally ignore them or indiscriminately prune them as a formal hedge. Regardless, over time they end up looking like a poodled giraffe - all leg with just a clump of leaves at the top.

To fill in plant bases with foliage is really easy. Every year during winter or early spring cut some of the oldest vertical stems down to the ground. This will encourage new stems to grow from the base. You can also cut back some of the oldest stems to 6-12 inches above the ground to encourage new buds to push from these stubs.

You can rejuvenate plants that are too tall and straggly in two stages. First, cut half the stems to 6-12 inches above the ground and wait a couple of months for them to send out new growth. Then cut back the remaining stems to the same height. In time plants will produce lightly branched cane-like stems with delicate, fine-textured foliage and live up to their name of heavenly bamboo. This method can also be used to rejuvenate any overgrown shrub that is multi-stem in growth habit.

Q. While pruning my hedges last week, I noticed several twigs dotted with white blobs. Upon close inspection the blobs looked more like a ridged shield with a tan top. These were clustered on boxwood and pittosporum bushes as well as on a well-established rosemary bush. Leaves were black and sticky and ants were crawling all around. What is going on?

A. You describe a cottony cushion scale infestation. The adult female insect can be yellow, orange, red, or tan and is noticeable by its elongated, fluted, white egg sac containing 600 to 800 eggs. When weather is warm eggs hatch in a few days. In winter months it may take two months. Baby scales, called 'crawlers', are red with dark legs and antennae. The adult male is rarely seen.

Cottony cushion scale damages plants by sucking sap from leaves, twigs, branches, and trunk. The scales excrete a sticky liquid called honeydew, which attracts and provides a food substrate for ants and also the black sooty mold fungus.

Natural enemies usually keep cottony cushion scale populations under control in the landscape. The vedalia beetle is a close relative of the common ladybug, only she is a little smaller and usually redder with more black spots. Native to Australia, she became famous in CA for saving the fledgling citrus industry from destruction by the cottony cushion scale in the 1890s. The vedalia beetle adult and larvae feed on all stages of the cottony cushion scale. The other important natural enemy to the scale is a very small parasitic fly.

Before reaching for the spray bottle, look to see if the vedalia beetle is present on your bushes. Ants slow down the progress of the vedalia beetle. The ants like the honeydew food source provided by the scale so they protect the scale by pestering the vedalia beetle. Control ants with Tanglefoot or stickem painted on duct tape or tree wrap and mounted on the trunks. Another option is to use ant baits. Prune to remove dense scale covered branches and to open the plant to more sunlight. If scale populations are extremely high and causing plant damage to occur, then use a narrow range, superior, or refined oil spray instead of a broad-spectrum insecticide. Spray when crawlers are active.

March 15, 2001