Butterfly Bushes and Willow Trees

Lilacs will bloom in different climates. Sisika/Shutterstock

Q: How and when do I trim my butterfly bush?

A: There are several species of plants commonly called butterfly bush. The most common ones are in the Buddleia genus. The most common one is Buddleia davidii, and it is also sometimes called summer lilac.

It flowers on the ends of the new growth from midsummer until frost. In the northern states, it is treated as a perennial, because the branches all die back to the roots each winter. As each cluster of flowers turns brown, they can be cut off. Cut the branch back to a pair of leaves or side branches. New side branches will continue to send out more flowers, and the plant will look nicer without the stalks of dead flowers hanging on the ends of the branch.

Before new growth comes out in the spring, cut all dead stalks back to the ground level. Do not try to yank them out of the ground like you can with the dead stalks of many perennials. The dead stems could pull the roots out of the ground.

In the middle states, the butterfly bush does not die to the ground each winter. After mild winters, you may get a much bigger and fuller plant when the previous year’s stems send out new growth. Wait to see how much dead material there is and prune it out, and then prune to shape the plant.

In southern states, this plant can grow to be a large shrub as much as 15 feet high. Prune out dead wood as necessary, and prune back old flower stalks to get more new growth that will bloom better.

The species Buddleia alternifolia is commonly called the alternate-leaf butterfly bush. It grows to a small tree (20 feet) and is only a little bit hardier than the other butterfly bush. It begins blooming a month earlier and is not as fragrant.

The main thing to know is that it blooms on the previous year’s wood, not on the ends of the new growth. It should be pruned in the month or so after it stops blooming, so that the new growth of that year will become the flowering wood of the next year. Pruning this plant in spring or even late fall will reduce the amount of flowering the next year.

Q: We have a willow tree in our yard that is infested with little black bugs. They make a red smear or mark when you brush them off. They have gotten progressively worse the past three years. What can we do?

A: Willows are often short-lived trees because they have so many insect and disease problems. They have weevils that have a larval stage that is a borer. They have beetles that have a larval stage that is a borer. They have beetles that eat holes in the leaves and eat all the leaf material between the veins. And last but not least, they have aphids that suck the juice out of the leaves and stems.

All of these insects can be black. The aphids gather in large numbers on the leaves and stems. They are also soft-bodied, so they are squishier. Aphids have a short digestive system, so the sap still has sugar in it when it leaves the aphid. The leaves and other objects (e.g., cars, tables) under an aphid colony may become sticky with the sap. A black, sooty mold may grow on the sap and make everything look rather dingy. Ants may be present in large numbers to protect the aphids from predators so they can have all the sweet sap to themselves.

All of these willow insects can be controlled with the same method. Use a systemic insecticide that soaks into the trunk and moves through the plant where the chewing and sucking insects can be exposed to it, but the good insects that do not eat willows will not be exposed.

Courtesy of Jeff Rugg

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