Cycas siamensis siamensis (2 years old seedling)
The rare silver form of  is a very striking plant, both glinting and elegantly characterized by its emergent leaves that are more silvery-grey than the standard species. The leaves retain much of this colouring over time. However the young seedlings are dark green in colour for some years.
 

Description: It is a short stemmed palm-like plant with a swollen trunk and an attractive crown.
Stem: Short very slow growing, arborescent to acaulescent up to 1.5 m tall, 14-20 cm diam. at narrowest point. The trunk has a wrinkled bark and red-brown tomentum at the leaf base. It has a well marked bulbous base, often becoming broad and plate-like in older individuals. Often the plants reach reproductive maturity before any aerial stem is developed.
Leaves: Annually deciduous, pinnate, with 140-280 leaflets inserted at 170-180° on rachis flat (not keeled) in section with a very short petiole and basal leaflets gradually reducing in size towards the spines usually 60-120 cm long, but occasianally up to (perhaps) 2 m. They also are usually densely brown-tomentose, with the tomentum persisting around their bases and on the trunk around the persistent leaf-bases. The leaves are usually dark green, but vary in colour from white through yellow, orange to brown, depending on the colour of the persistent hairs above and below on the leaves. There are no other clear distinguishing features, and they must all be regarded as the same species. The woolly white form is often sold as "Silver" or "Thai Silver" form.
Male cones: Small of a distinct oblong shape, orange to brown, 10-24 cm long, 5-7.5 cm diam.
Seeds subglobose: 30-37 mm long, 26-37 mm wide.
 

Three years old.  The leaves are annually deciduous, the older gradually fade as the fresh start growing.

Warning: All parts of this plant are highly toxic, but rarely eaten due to poor flavour.

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Scientific name:  Cycas siamensis Miq.
Published in: Bot. Zeitung, Berlin 21: 334 (1863)

TYPE: Thailand, Kanchanaburi, "Siam, prope Kan-Boeric in collibus lapidosis" m. Martii 1862, J. E. Teysmann s.n., Mar. 1862 (holo U, 2 sheets).

Origin:  Central Thailand and Vietnam. Also recorded from Laos, Cambogia and Myanmar (Burma).

Habitat:  It is a widespread and locally extremely abundant species, it is found in many places in dry open deciduous forest on poor rocky soil to 1200 m. This species occurs in full sun to light shade on flat country or on low hills, often in dense stands. These woodlands are characteristically seasonally wet and dry with the monsoon weather patterns of the region, with particularly pronounced and extended dry periods.

Conservation status: Listed in CITES appendix 2.

Common English Names include: "Silver Cycas" or "Thai Silver Cycas"

Etymology: From the occurrence in Thailand, known as the Kingdom of Siam when this species was described.

Synonyms:

• Epicycas siamensis (Miq.) de Laub.
• Cycas immersa
• Cycas aurea
• Cycas cochinchinensis

Cultivation: Ideal for the tropical to warm temperate garden and particularly adapted to pot culture, it requires partial sun and a well drained soil.   In cultivation, at least in cooler climates, it is one of the few deciduous cycads, losing its leaves every winter. Coming as it does, from areas with high annual rainfall, it requires a plentiful supply of water and should never be allowed to dry out, but eventually it could stay dry for a long time. it's a bit fastidious for this climate- prefers it wetter and warmer (In temperate climate  the plant might be treated like a succulent and kept rather dry and cool during the winter)

Propagation: Easy to germinate ,

Point of interest: Silvery foliage makes this new cycad very spectacular.