A special committee was appointed by D.S.Senanayake, the first prime minister of Sri Lanka for the formulation of a national Flag for Sri Lanka. The current National flag is an improvisation of the civil standard of Sri Lanka's last king, Sri Wickrama Rajasingha.
The National Flag of Sri Lanka symbolizes the country's culture and heritage and embodies the spirit of nationality of its people. It also represents the four virtues of kindness, friendliness, happiness and equanimity. Each element on the National Flag has a distinctive symbolic significance. The first time the National Flag was hoisted was on 3 March, 1950.
A National Emblem essentially symbolizes a nation. As a British Crown Colony Sri Lanka used the British Emblem and continued to use it even after the attainment of its independence in the year 1948. Hence a select committee was appointed to create a state emblem more suited for Sri Lanka.
The new state emblem includes a lion with a sword in its right front paw surrounded by a Palapethi open petal design top. Beneath this, there is a strip carrying the country's name in Sinhala, Tamil and English.
On being declared a Republic on 22 May, 1972, Sri Lanka further adopted a new Republican Emblem which had an additional portrayal of Punkalasa, dhammachakka, sun, moon and two sheaves of paddy besides the lion with a sword.
The National Bird of Sri Lanka is the Wali Kukula or the Ceylon Jungle fowl which is the most common bird found in the national parks and forests.
Since the year 1986, the ‘Nil Mahanel ' has been the national flower of Sri Lanka. The botanical name of this flower is “Nympheae Stelleta” and is found in all parts of the country.
On 26 February, 1986, the Cabinet had adopted the Na Tree as the national tree of Sri Lanka because of the country's close association with the tree for centuries both socially and culturally. The Na tree has its origins in Sri Lanka itself.
123independenceday.com gives a summary of the National Symbols of Sri Lanka