Spreading Crassula

Crassula decumbens Thunb.

Synonyms - Crassula macrantha, Tillaea macrantha.

Family: Crassulaceae.

Names:

Crassula is from the Latin crassus meaning thick and referring to the fleshy leaves and stems.
Spreading Crassula.

Other names:

Rufous Stonecrop.
Spreading Stonecrop.

Summary:

A small, fleshy, green to red leaved, annual herb, with prostrate stems.

Description:

Cotyledons:

Two. About 1 mm and round to oval. Fleshy pimply and hairless.

First leaves:

Oval, fleshy, pimply and hairless.

Leaves:

Opposite. Almost round.
Petiole - None.
Blade - Green to red/brown, narrowly egg shaped to oval, 3-8 mm long x 1-2 mm wide, Slightly constricted towards the base, convex on top and below, fleshy, pimply. Tip acute.

Stems:

Erect or decumbent, 20-100 mm long, weak, round, many dichotomous branches. Hairless. Forms a mat on the ground.

Flower head:

One to several, terminal or axillary, in cymes forming a broad corymbose panicle which occupies the majority of the plant.

Flowers:

White to pink, bisexual, regular, 4-6 mm wide. On stalks, 4-10 mm long that are longer than the leaves.
Ovary - Superior with a small flat scale at the base. 4-5 carpels elongated, kidney shaped in outline, gradually constricted into thin styles. 4-12 ovules. Scales wedge to T shaped, often crimson, 0.2-0.4 mm long.
Sepals - 4-5, green, fleshy, lobes narrowly ovate, 1.5-3.5 mm long, fleshy. Hairless or with a few hairs near the acute tip.
Petals - 4-5, white to cream or pink, lobes narrowly ovate, 1.5-2 mm long, spreading. Tip acute.
Stamens -
Anthers -

Fruit:

4-5 smooth, slightly curved follicles. On stalks to 8 mm long. Seeds released through an apical pore. 4-12 seeds in each follicle.

Seeds:

Very small, usually ridged, warty, covered with minute white papillae.

Roots:

Shallow.

Key Characters:

Calyx longer than corolla. 3-18 flowers in the axils of both leaves at each node. Inflorescence elongated, terminal or axillary. Calyx lobes acute but without a mucro. Flowers with pedicels to 30 mm long. Seeds released through apical pore of follicle. Carpels with 4-22 ovules. Calyx lobes smooth or with a few papillae at the apex. Lateral cymes (dichasia) pedunculate. Flowers 5 merous (the synonym Crassula macrantha is usually quoted to have 4 merous flowers).
From Marchant et al

Biology:

Life cycle:

Annual. Germinates anytime with a peak in winter. Makes active growth in winter and spring. Flowers late-winter/spring. Dries to a pink fragile mat on the soil after flowering as summer approaches.

Physiology:

Reproduction:

By seeds.

Flowering times:

August to October in WA.
September to December in SA.

Seed Biology and Germination:

Vegetative Propagules:

Hybrids:

Allelopathy:

Population Dynamics and Dispersal:

Spread by seed.

Origin and History:

Australia.

Distribution:

ACT, NSW, SA, TAS, VIC, WA.

Courtesy Australia's Virtual Herbarium.

Habitats:

Prefers shaded situations.

Climate:

Temperate.

Soil:

Prefers damp soils.

Plant Associations:

Significance:

This is the most common Crassula species in dry land crops in WA.

Beneficial:

Detrimental:

Weed of crops, disturbed areas and wet areas.

Toxicity:

Not recorded as toxic.

Legislation:

None.

Management and Control:

Thresholds:

Eradication strategies:

Sensitive to low rates of diuron.

Herbicide resistance:

Biological Control:

Related plants:

Australian Crassula (Crassula sieberiana)
Crassula (Crassula colorata)
Three-parted Crassula (Crassula alata)
Swamp Crassula (Crassula helmsii)
Crassula ciliata
Crassula glomerata
Crassula multicava
Crassula natans
Crassula tetragona

Plants of similar appearance:

Chickweed (Stellaria media)
Corn Spurrey (Spergula arvensis)
Four-leaved Allseed (Polycarpon tetraphyllum)
Mouse-eared Chickweeds (Cerastium spp.)
Pearlwort (Sagina apetala)
Pimpernel (Anagallis arvensis)
Waterblinks (Montia spp.)
Pigweed (Portulaca spp.)

References:

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P392.

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P190-191.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P341. Photo.

Gilbey, D. (1989). Identification of weeds in cereal and legume crops. Bulletin 4107. (Western Australian Department of Agriculture , Perth). P57. Photos.

Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).

Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. and Macfarlane, T.D. (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P205.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.