Crassula ovata
(jade plant)

Crassula ovata is a large, much-branched, hairless and floriferous shrub from southern Africa. Commonly known as the jade plant or money plant, C. ovata has been grown as an indoor ornamental in Europe, North America, East Asia and practically worldwide for over a hundred years. It is also popular as a landscape plant in mild climates. Its popularity as an ornamental plant arises primarily from its ease of propagation by cuttings. It is this characteristic that has allowed it to escape into the wild and become weedy in some areas outside its natural range. Given the century or more in cultivation, ease of vegetative propagation and virtual worldwide distribution in homes and gardens, it is perhaps surprising that C. ovata is not significant as an invasive weed.

C. ovata is native to South Africa, where it grows in Cape Province, KwaZulu-Natal and the Transvaal (Bramwell, 2015; USDA-ARS, 2015). In Eastern Cape it is fairly common from Willowmore to East London and northwards to Queenstown (Court, 2000). It is also found in Mozambique (Bramwell, 2015; USDA-ARS, 2015) and Swaziland, where it is considered a nationally threatened non-CITES species due to its collection from the wild for the succulent plant trade (Fragoso et al., 1999).

Byalt (2011) reports C. ovata as adventive in Spain, while Verloove (2013) comments that it is sometimes seen as a garden escape in the Canary Islands. Individual specimens have also been observed in the wild in New Zealand, Australia and Mexico (iNaturalist, 2015).

The best documented instances of C. ovata as an invasive species are, however, from the USA. Although not on California’s list of noxious weeds, it is naturalized in warmer wetlands, coastal areas and in many canyons near urban areas in southern California (Hoyt, 2015). It persists from cultivation at the urban-wild land interface and at waste dump sites at elevations below 100 m (Boyd, 2013). It has been identified in the San Francisco area of northern California, as well as Monterey County, and in Santa Barbara, Los Angeles, Orange and San Diego Counties in the south (Calflora, 2015). Typically, sites where C. ovata has been identified include steep south-facing slopes, among dunes, canyon bottoms, along trails, on the edge of mesa and in fallow fields (Consortium of California Herbaria, 2015).

On Kauai, Hawaii, C. ovata has been found naturalized locally on cliffs with other succulents in secondary Leucaena thicket. A single specimen was collected in Hanapepe in Waimea district, on the Awawa Road along Hanapepe River, below Hanapepe Heights at 12 m elevation in 1993 (Lorence et al., 1995). 

As a highly valued and frequently traded ornamental species, widely available through the nursery trade, it is highly likely that C. ovata will be further introduced to new areas. It has the potential to spread rapidly and easily from leaves and pieces of stems that break off, root and grow.

In its native range, C. ovata is a prominent component of valley thicket vegetation of the Eastern Cape and KwaZulu-Natal, South Africa, found particularly on dry, rocky hillsides (Mahr, 2010). Known as Albany thicket, this habitat is dominated by grasses and mixed succulent communities of aloes and euphorbias, as well as other native shrubs and herbs (Bramwell, 2015). In the Eastern Cape it experiences frequent droughts, unpredictable rainfall patterns (ranging typically from 250 to 550 mm per annum) and a maximum temperature of 40°C. In arid coastal habitats, the presence of hydathodes on adaxial leaf surfaces may be important in absorbing water from coastal fog (Jones, 2011).

Genetics

The chromosome number of C. ovata is 2n = 42 (International Crassulaceae Network, 2015).

Reproductive Biology

Pollination of C. ovata is insect-mediated. The flowers have a faint, sweet scent and attract bees, wasps, flies, beetles and butterflies for pollination.

Physiology and Phenology

The presence of Crassulacean Acid Metabolism (CAM) in C. ovata and other Crassula species allows plants to reduce water loss from leaves without limiting photosynthesis. With CAM, stomata are closed during the day but open at night when the carbon dioxide taken in is stored in the form of organic crassulacean acids. During the day, these acids are broken down and the carbon dioxide released is re-used in the photosynthetic process. In this way, plants lose much less water yet can photosynthesize normally during daylight hours. In addition, under extremely dry conditions, stomata can remain closed at night and will re-cycle the carbon dioxide within cells (Malan and Notten, 2005).

In arid coastal habitats, the presence of hydathodes on adaxial leaf surfaces may be important in absorbing water from coastal fog (Jones, 2011).

C. ovata is an important model species for the study of CAM regulation and stomatal opening, and there are numerous research papers on these aspects; see for example, Loucks and Ownby, 1978; Rustin et al., 1988; Nose, 1992; Kawamitsu et al., 2002.

Longevity

It is popularly believed that C. ovata plants can live for decades under cultivation, and according to Aspen (2015), even up to 100 years.

Environmental Requirements

C. ovata plants are tolerant of a wide range of temperatures and humidities, and may even tolerate light frost, but will be killed by freezing conditions. Although they are succulent plants, they do need water, and prolonged drought can result in dwarfing, foliage spotting, leaf drop and death (Mahr, 2010).

In the Eastern Cape of South Africa it experiences frequent droughts, unpredictable rainfall patterns (ranging typically from 250 to 550 mm per annum) and a maximum temperature of 40°C. 

Outdoors in the USA, C. ovata can grow in USDA plant hardiness zones 10A to 11, tolerating some winter cold (to -1.1ºC); prolonged cold, however, is usually fatal (PIER, 2005). C. ovata can grow in partial shade, but it needs sun for flowering. Overexposure to direct sun or heat can scorch the leaves and lead to leaf drop (Hoyt, 2015).

Ideally, C. ovata prefers mildly acidic (pH 6-6.5), dry, well-drained soil. It tolerates various soil types, including loamy, sandy, acidic, neutral and slightly alkaline. It tolerates wind, salt and coastal conditions, but is humidity intolerant (PIER, 2005). Costello et al. (2003) consider its salinity tolerance to be low to intermediate.

According to the 1984 Index of Plant Diseases of Florida (Alfieri Jr et al., 1984), C. ovata, grown as an ornamental, is susceptible to infection by representatives of 10 fungal genera (Oidium, Alternaria, Ascochyta, Bipolaris, Cercospora, Corynespora, Diplodia, Fusarium, Phyllosticta and Pythium), as well as 3 specific fungal species (Alfieri Jr et al., 1984; Farr and Rossman, 2015).

In addition, Braun et al. (2003) recorded the presence in Germany of Oidium kalanchoës [Pseudoidium kalanchoës] for the first time on C. ovata, while Kiss (1999) reported a powdery mildew caused by an Oidium species for the first time in Hungary. Ortu et al. (2013) identified a new forma specialis of Fusarium oxysporum infecting C. ovata in northern Italy.

C. ovata has few insect pests, but in South Africa it has been identified as a wild alternative host for Thaumatotibia leucotreta [Cryptophlebia leucotreta] (false codling moth), which may have implications for C. ovata in the management of the pest in citrus orchards (Kirkman and Moore, 2007). As a domestic and greenhouse plant, C. ovata is also prone to attack by sap-sucking mealybugs (Pseudococcidae) worldwide (Mahr, 2010) and as such can act as a dispersal vector for exotic mealybug species. For example, Vryburgia amaryllidis, the lily bulb mealybug, and V. brevicruris, the short-legged mealybug, are often intercepted on plants entering the south-eastern region of the USA where they are not as yet established pests (Hodges et al., 2005).

Medicinal, pharmaceutical

• Traditional/folklore

Ornamental

• Potted plant

In South Africa, C. ovata can be confused with the very similar Crassula arborescens. However, the latter occurs only in the Little and Central Karoo and has a distinct waxy bloom on its leaves; in addition, its leaves are blue-grey and almost spherical (Malan and Notten, 2005; Mahr, 2010). In Hawaii, C. ovata can be distinguished from C. multicava and C. sieberiana, two species already classed as naturalized on the islands, by its larger habit, larger leaves, and differences in leaf and flower morphologies (Lorence et al., 1995).

The invasiveness of C. ovata needs more research to determine whether it has the potential to become a problem in habitats similar to those of its native range in South Africa, such as in California.

23/03/15 Original text by:

Andrew Praciak, Carne, Wexford, Ireland