Love-in-idleness is another name for the wild pansy

It is the flower mentioned in the works of William Shakespeare

William Shakespeare

William Shakespeare was an English poet and playwright, widely regarded as the greatest writer in the English language and the world's pre-eminent dramatist. He is often called England's national poet and the "Bard of Avon"...

 that inspired love.

In A Midsummer Night's Dream

Shakespeare uses the flower as a plot device in A Midsummer Night's Dream

A Midsummer Night's Dream

A Midsummer Night's Dream is a play that was written by William Shakespeare. It is believed to have been written between 1590 and 1596. It portrays the events surrounding the marriage of the Duke of Athens, Theseus, and the Queen of the Amazons, Hippolyta...

. Oberon plots to take revenge on Titania and sends Puck

Puck (Shakespeare)

Puck, also known as Robin Goodfellow, is a character in William Shakespeare's play A Midsummer Night's Dream that was based on the ancient figure in English mythology, also called Puck. Puck is a clever and mischievous elf and personifies the trickster or the wise knave...

 to retrieve the flower:
Oberon's account is that he diverted an arrow from Cupid

Cupid

In Roman mythology, Cupid is the god of desire, affection and erotic love. He is the son of the goddess Venus and the god Mars. His Greek counterpart is Eros...

's bow aimed at "a fair vestal

Vestal

Vestal can refer to:* Pertaining to Vesta , a Roman goddess, the Sacred fire of Vesta, or the Temple of Vesta* Vestal Virgin* Vestal, New York* HMS Vestal, the name of eight ships of the Royal Navy* USS Vestal , ship...

, throned by the west" to fall upon the plant. The "imperial vot'ress" passes on "fancy-free", destined never to fall in love. The juice of the magical purple love-in-idleness flower became a love potion

Love potion

Love potion may refer to:* In folklore, mythology, or works of fiction, a love potion may refer to a type of potion designed to create feelings of love towards a person* Lappish Hag's Love Potion, an alcoholic drink* The Love Potion, a painting...

: When dripped into someone's eyes cause that individual to madly dote upon (fall in love with) the next person they see. Equipped with such powers, Oberon and Puck control the fates of various characters in the play to provide Shakespeare's essential dramatic and comic structure for the play.

In The Taming of the Shrew

Shakespeare mentions it in his play The Taming of the Shrew

The Taming of the Shrew

The Taming of the Shrew is a comedy by William Shakespeare, believed to have been written between 1590 and 1591.The play begins with a framing device, often referred to as the Induction, in which a mischievous nobleman tricks a drunken tinker named Sly into believing he is actually a nobleman himself...

where Luciento claims he found the effect of love-in-idleness - alluding to its qualities to simulate the effects of love.