The Timing to Prune Senecio

Varieties

• A widely-grown plant called dusty miller (Senecio cineraria) is a member of this large group, getting its name from the dusty-silver, velvety appearance of its leaves. A perennial that grows outdoors year-round in U.S. Department of Agriculture plant hardiness zones 7 through 10, it's about 1 foot tall and has foliage that contrasts well with other plants. Other varieties in the genus include a 1- to 2-foot plant called blue finger (Senecio talinoides var. mandraliscae), because its succulent blue-green leaves resemble upright fingers, and another plant called large kleinia (Senecio aizoides), a creeping specimen with 3- to 6-inch, thick bluish leaves on stems that can be 5 feet long. These two plants grow in USDA zones 10 through 11 and 9 through 11, respectively.

Timing

• Dusty miller, blue finger and other plants in this genus grow quickly in warm weather, generally from spring through late fall. The best time to prune plants is early spring, when you can remove any dry or winter-damaged leaves and stems, and cut the plants back to encourage new, bushy growth. Some plants in this group, such as dusty miller, survive frost in colder areas, but the entire plant often dies back to the ground. For these plants, you can remove old leaves and stems in spring, before new growth begins. Dusty miller, blue finger and other varieties tend to become leggy as the season progresses and benefit from pinching or pruning back in mid- to late summer.

Pruning

• When pruning dusty miller, blue finger or another variety that's beginning to look leggy, cut stems back by one-third or one-half, using pruning shears or a sharp knife. You can also remove flower buds as they appear in late spring or early summer, because the flowers are inconspicuous and removing buds promotes new shoots at branch ends. This helps expands the plant's width and makes it denser and bushy. In areas with cold winters outside the normal range of these plants, grow these plants as annuals, taking cuttings from young, healthy stems in fall to make new plants for over-wintering indoors. Dip cut ends in rooting hormone, which is available at garden centers, and place the cuttings in moist sand or potting soil to root.

Other Requirements

• Cultivated varieties of the genus Senecio grow in either full sun or partial shade, but they develop the best leaf color in full sun and tolerate strong, hot sun well. The plants grow in any type of garden soil that's well-drained, and semi-succulent types such as blue finger are especially intolerant of wet, soggy soil. If your soil is high in clay and drains slowly, add sand at planting to improve its drainage. These plants have no serious pest or disease problems, provided they are grown in well-drained soil and their roots don't stay constantly wet, which can promote fungal problems.