Senecio are members of the family Asteraceae, the same family the daisies are found in. Some of the common names for Senecios are ragworts and groundsels. Most of the succulents species are not called either, however. Some of the plants I first learned to be Senecios are now known as Kleinia so I will at least mention this group.
Here's an example of a Ragwort, Senecio flaccidus... a drought-tolerant plant but NOT a succulent Senecio
Examples of two more relatively common Senecios that are NOT the succulent variety: Senecio bicolor subsp. cineraria (aka dusty miller) and Senecio mikainioides (aka cape ivy- photo Mystic)
Though flowers may be a plus with some non-succulent Senecios... (here Senecio polyodon left- photo growin; Senecio confusus middle- photo RWhiz; and Senecio petasitis right- photo Calif_Sue)...
Succulent Senecio flowers are rarely much to look at (Senecio talinoides left and Senecio kleiniaeformis middle); an exception is Senecio stapeliiformis right (photo Franj)
There are about a dozen succulent Senecios I have found to be excellent garden and container plants in my xeriphytic landscape. They are among a collection of potted things I can ignore for long periods without worrying about them dying from lack of water or attention. Some are the perfect groundcover landscape plants for large open areas (no longer in existence in my garden) or for planter boxes in need of something that drapes over the edges. Some Senecios are the best hanging plants I have. And some are just curiosities I see frequently in the cactus and succulent shows, though most of these are a bit too touchy for my personal growing practices.
As a group, most of the commonly grown succulent Senecios are very drought-tolerant, heat-tolerant and even relatively cold-tolerant. Some succulent species are rot prone, but fortunately those ones are not usually the common species. Their colors range from deep green to a wonderfully chalky blue color, with purplish, striped and variegated forms existing as well.
As a group, Senecios are one of the more toxic plants and have been known frequently to cause significant toxicity in farm animals which eat groundels and ragworts indiscriminantly. However specific cases of toxicity from any of the succulent species are very scarce and I could not find a single reported toxic exposure to one of these plants in my searches for one. However, avoid putting pets and children at risk as some Senecio species have potent liver toxins; it is better to be safe than sorry.
The following will be a discussion of some of the more common succulent Senecios in cultivation and certainly not an all-inclusive treatise of the genus Senecio.
Senecio articulatus, aka candle plant, is a very commonly sold species of Senecio, at least in southern California nurseries. It is grown mostly as an oddity in pots. This is a thick, tubular, striped species that is leafless half the time and looks a bit like a Euphorbia. This is definitely not one of the easier species for me to keep alive--multiple attempts have all ended in mound of rotten mush. This one is strictly for those naturally blessed with the talent for keeping easy-to-rot succulents alive, or who have some self control when it comes to watering things.
Senecio articulatus as a potted plant (left photo Happenstance) and in a botanical garden (right)
Senecio crassissimus, or vertical leaf senecio, is a nice looking, turquoise to purplish species with flat, suuculent, vertically oriented leaves. This one has turned out to be relatively easy to grow and less apt to rot than it looks like it might. Mine grows in mostly full sun and has had no problems with extreme heat or cold down into the mid-20s F.
Senecio crassissimus photos (right photo mgarr)
Senecio ficoides, aka Blue Chalk Sticks, is a relatively rare ‘blue ice plant' at least compared to the other two Blue Chalk Stick species. This is the largest of the three and sort of a slow grower. Otherwise, it seems pretty similar in all other respects (see Senecio talinoides below).
Senecio ficoides in southern California
One of my favorite of all the Senecios is Senecio haworthii. Though this is another fairly easy-to-rot species, I find that I can keep it alive. A very slow grower, this plant tends to stay pretty small, growing maybe 18 inches high in many years. Its main obvious attraction is that it is nearly pure white, and stands out nicely both as a potted plant and in the landscape. The leaves are a short, elliptically tubular shape covered with a shiny, silvery layer of scales. Though I am sure it does, I have yet to see a single one of these in flower.
Senecio haworthii in my garden (left), old plant in a nursery (center) and in landscape southern California (right)
Senecio kleiniaeformis, (Spear Head), is another blue groundcover species. This one is a bit slower growing and makes a decent potted plant as well. Though not as blue (usually) as the "blue chalk stick" Senecios, this one does look somewhat similar, but has a diamond-shaped leaf tip. It also has pale yellow flowers instead of white. The photo at the top of this article is this species, too.
Senecio kleiniaeformis photos (left photo Calif_Sue)
Senecio jacobsenii (syn. Kleinia petraea), or Weeping or Trailing Jade is another excellent potted succulent species. The leaf shape and color is very similar to that of a Crassula ovata (or jade plant); hence the name. This is a slow grower, but highly tolerant of a wide variety of conditions including low light, sun, cold, heat, and excess water. Though I include this here as a Senecio, more correctly this is one of the Senecios that has been reclassified into the genus Kleinia. Since I don't really know the difference, and just about every nursery selling this plant still lists it as a Senecio, for the sake of confusion I have done so as well.
Senecio (Kleinia petraea) jacobsenii
Senecio radicans, (String of Bananas or Necklace Plant) is a common succulent species in cultivation. I have many Senecios in my garden that closely resemble this species, but may actually be something closely related. However, they grow aggressively and are quite hardy as this one is. Of the common hanging string-form of Senecios, this one is by far the easier to grow and maintain in a garden or pot. It is much less prone to rot and much more sun/shade tolerant. In fact, in my garden, I have not found a good way to kill it accidentally as I have for most other succulent species. It tolerates lots of water and virtually no water (to a limit I have discovered), full, hot sun over 110F, permanent shade, cold (at least down to 25F which is as cold as it gets here) and attacks from insects. I would consider this one of my top ten easiest succulents to grow. Though it can be grown as a ground cover, it becomes a big mess as one so I don't really recommend it for that. I have found that this species is very easy to grow from ‘cuttings' and sometimes even fallen strings of plant reroot right on the surface of the soil. Flowers are relatively unsightly and small.
Senecio radicans photos (all by Happenstance)
photos of my Senecio radicans-like plant
Senecio rowleyanus, (String of Beads or Pearls), is one of the most commonly sold and grown succulent Senecios throughout the country. It is a curious plant indeed, comprised nearly entirely of spherical ‘leaves' connected by a very narrow, string-like stem. Flowers are white, puffy and less than impressive. Despite its commonplace occurrence, this is not the easiest plant to grow. In my southern California climate it is best to just water when dry and do very little else. It is prone to rot if overwatered, and burns badly in hot, full sun. However it seems to like as bright a light as possible and resents being in dark shade. Though it is very drought-tolerant, not watering it at all when hot and dry will cause the spheres to shrink and the strings to break apart and fall off. Cold, damp weather is tough on it, too, unless allowed to dry out periodically and kept above freezing most of the time. In the PlantFiles, it is listed as cold tolerant down to 10F but I find that hard to believe. However it never gets cold enough in my area (thank goodness!) for me to find out what its cold tolerance really is. As an indoor plant it performs quite will in bright light, but is prone to mealy bugs, so keep on the lookout for pests. This plant performs best as a potted plant with hanging strings of spheres and can be quite ornamental. In my climate, a warm Mediterranean one, it can be grown as a ground cover as well.
Senecio rowleyanus (variegated in second two photos)
Senecio rowleyanus in a pot and as a groundcover
though obviously closely related, this is an unknown Senecio I have in the garden that looks similar and grows exactly like Senecio rowleyanus
Senecio scaposus is a very attractive, thick rosette of numerous tubular, peeling leaves that have an over grey to silvery-green coloration. Some forms have a spoon-shaped leaf tip. This is a great potted plant for full sun, but watering must be done with great care at it rots pretty easily. This is one of those succulents that detests water when it's super hot out... just when one would think a plant might need water most. I invariably forget this fact and water it anyway... which is why I no long own any Senecio scaposus.
Senecio scaposus colors and forms
Very old garden plant (left); showing new growth color (middle); this is an easy plant to rot (right shows one of two plants rotting in same pot)
Senecio serpens (aka blue chalk sticks or blue ice plant) is perhaps the best-looking of the three blue chalk stick Senecios, with relatively short, compact and extremely pale blue tubular leaves. This plant grows as a low, neat groundcover and makes an very ornamental pale blue swath in full sun in warm climates. As for cultivation, it is pretty similar to the more common Senecio talinoides (aka mandraliscae) below.
Senecio serpens in Southern California
Senecio serpens is an excellent landscape plant to grow around other succulents as it stays short and does not compete with them visually; flowering (right)
Senecio talinoides (syn. Senecio mandraliscae) or blue chalk sticks, is one of at least 3 species of Senecio with this common name. Some consider this a hybrid ‘species' between Senecio mandraliscae and Senecio aizoides while others say Senecio talinoides is the true species and the other two are just subspecies of Senecio talinoides (which is how I will keep it in this article). This species is similar to Senecio ficoides and S. serpens and personally I have a hard time telling them apart sometimes. It does not help that some websites are obviously confusing them as well. All are called Blue Chalk Sticks and all have the same white, puffy, uninteresting flowers. Only their overall leaf size and growing habits vary a little. Senecio talinoides may be the most aggressive of these species, but I have not grown all three to know that for sure. All are cold-hardy down to the mid-20s F and are excellent groundcover succulent species. Some call these Senecios the blue ice plants since they have a similar appearance and growth habit. I find all these blue chalk sticks to be some of the easiest of all the Senecios, tolerating a wide variety of growing conditions from extreme heat and blazing sun to shade, to high moisture (low rot potential for this one) to being very drought-tolerant. These species do tend to get sort of leggy, which is particularly a problem if grown as a potted plant, and yearly trimming back is often necessary.
Senecio talinoides in Huntington Gardens, Southern California
Some consider Senecio cylindraceus to be a subspecies of Senecio talinoides, so I include these photos of Senecio cylindraceus here. This plant grows similarly but has much thinner leaves and tends to grow taller, up to two feet.
There are many other succulent species of Senecio in cultivation (see below) but these are the most common ones I come across or grow with regularity.
Senecio acaulis Senecio barbertonicus Senecio crassifolius
a caudiciform species: Sencio deflersii (left); Senecio oxyriifolilius (center) Senecio pendula (right)
Senecio stapeliiformis (left) Senecio vitalis (photo Kell) middle Senecio saginata (right)
Two large, succulent Senecio species that have now been moved to other genera: Kleinia nerifolia (left) and Pittocaulon praecox (left)