What is senecio? There are more than 1,000 varieties of senecio plants, and about 100 are succulents. These tough, interesting plants may be trailing, spreading groundcovers or large shrubby plants. Let’s learn more about growing senecio plants, along with some important caveats.
I. Appearance and CharacteristicsÂ
Senecio is a genus of flowering plants in the daisy family (Asteraceae) that includes ragworts and groundsels.
Variously circumscribed taxonomically, the genus Senecio is one of the largest genera of flowering plants.
The genus Senecio is distributed almost worldwide. It is one of the few genera occurring in all five regions with a Mediterranean climate. Furthermore, species are found in mountainous regions, including tropical alpine-like areas.
Morphology
The flower heads are normally rayed with the heads borne in branched clusters, and usually completely yellow, but green, purple, white and blue flowers are known as well.
In its current circumscription, the genus contains species that are annual or perennial herbs, shrubs, small trees, aquatics or climbers. The only species which are trees are the species formerly belonging to Robinsonia occurring on the Juan Fernández Islands.
Chemistry
Pyrrolizidine alkaloids are found in all Senecio species. These alkaloids serve as a natural biocides to deter or even kill animals that would eat them. Livestock generally do not find them palatable. Senecio species are used as food plants by the larvae of some Lepidoptera species that have developed tolerance for these alkaloids.
The traditional circumscription of Senecio is artificial, being polyphyletic, even in its new circumscription which is based on genetic data. Despite the separation of many species into other genera, the genus still contains c. 1,250 species and is one of the largest genera of flowering plants.
As no morphological synapomorphies are known to determine which species belong to the genus or not, no exact species number is known. The genus has an almost worldwide distribution and evolved in the mid- to late Miocene.
II. Types of Senecio
There are many dozens of succulent Senecio species. Here are just a few of the well-known varieties:
- Lavender steps, propeller plant (S. crassissimus): This low maintenance variety is an easy grower that can handle some frost. It features bluish, flattened leaves on an upright plant. It grows 18 to 24 inches tall with an 18-inch spread, and is hardy in USDA zones 10 to 11.
- Cocoon plant (S. haworthii): “Cocoon” refers to the shape of the gray leaves, which form a prostrate bush but do require periodic renewal. This plant grows to 1 foot high with a spread of up to 3 feet, and is hardy in USDA zones 9 to 11.
- String of bananas (S. radicans): This variety is more tolerant of shade and moisture. It features puffing, crescent moon-shaped leaves that punctuate long stems. It grows 6 to 12 inches tall with a similar spread, and is hardy in USDA zones 10 to 12.
- String of beads, string of pearls (S. rowleyanus): This plant is comprised of dangling stems of round leaves, and does well with minimal watering. it is a trailing plant that can extend 3 to 5 feet, and is hardy in zones 9 to 12. It is often used in hanging baskets.
- Blue Chalksticks (S. serpens): This variety has short, steel-blue, tubular leaves. It grows 12 to 18 inches tall with a spread of 18 to 24 inches, and is hardy in zones 10 to 11.
- Blue Chalksticks (S. mandraliscae) is similar to S. serpens but a more vigorous grower with pencil-like leaves.
III. How to Grow and Care
Sunlight
In hot climates, the plants prefer bright indirect light whereas in cooler climates, they should get full sun.
Temperature and Humidity
Most varieties thrive in USDA Hardiness Zones 9 to 12. As with the majority of succulents, they’re heat-tolerant. A few Senecio species can withstand brief periods of cold or dampness, but prolonged exposure to cold will turn them to mush.
Watering
As succulents, these plants have excellent tolerance for drought. For most types, allow the roots to dry out completely between waterings. Soaking in water will cause the roots and plants to turn mushy.
Soil
The plants aren’t particular about soil pH and do fine in the neutral range (6.0–7.0). More importantly, make sure the soil is well-drained and on the sandy side. For potted plants, use a fast-draining succulent or cactus soil mix.
Fertilizing
Since Senecio plants grow in sandy soil, the nutrients will need to be replenished. Fertilize annually, but lightly. Too much fertilizer can cause an abundance of leggy growth.
Pruning
Pruning trailing Senecio succulents, like String of Pearls or String of Bananas, involves trimming leggy stems, removing unhealthy growth, and dead or damaged leaves, and shaping the plant as desired. When you trim off the stems, cut them just above leaf nodes so these stems can be kept for propagation.
For compact, shrubby Senecio plants, prune to control size, thin out overgrowth, deadhead spent flowers, and maintain a tidy form. Don’t forget to use only clean, sharp tools for clean cuts and minimize damage. Regular pruning keeps your Senecios healthy and vibrant.
Propagation
Rooting cuttings is the easiest and fastest way to propagate Senecio plants. This is best done during the growing season between autumn and spring, While the size of the cutting depends on the species, the overall process is the basically the same as for planting succulent cuttings:
- Take a cutting and let it callous over for a few days.
- Dip the cutting in rooting hormone and plant it in a container filled with well-draining potting mix.
- Start watering only once roots have developed.
How to Grow from Seed
Because Senecio is so easy to propagate from cuttings, it is the most commonly practiced propagation method. Senecio is rarely sold as seeds.
Potting and Repotting
When potting, use a well-draining pot or container with drainage holes. Senecio succulents prefer containers made of terracotta, ceramic, or other breathable materials, which help excess moisture evaporate. For trailing Senecios, select a container that allows for the trailing growth habit. Hanging baskets or containers with wide openings are excellent choices.
When repotting, select a pot that is just slightly bigger (about 1 size or 10% larger) than the current one. Using a too-big pot can lead to overwatering issues, as the excess soil retains more moisture. Handle the delicate stems with care to minimize damage and reduce transplant shock. Repotting should be done only during the growing season unless your plant is having some rotting or disease problems and needs to be repotted right away.
Overwintering
In colder climates, potted Senecio plants need to be brought indoors during the winter months. Give the plants the brightest, sunniest location you can find and water them when the soil feels dry to the touch.
Pests and Diseases
Few pests bother Senecio plants, but they can occasionally be affected by scale and mealybugs. If this happens, try treating it with neem oil or insecticidal soap.
