Blue Lace is also known as Secret Potion and Bachelor's Downfall.
Blue Lace grows upon the surface of the water in sheltered coves of the Mediterranean. It has a blue-green cast to its form, much like common algae, which it resembles. The identifying mark is the red and yellow flowers that bloom each full moon. These flowers are about the size of a Muggle matchstick head.
Blue Lace is rated 4. A person is able to use this plant a maximum of three times. If used more than three times, an unsightly (and permanent) sprouting of purple fungus growth protrudes from the nose and ears.
It is remarkably easy to grow Blue Lace. Simply obtain waters from any body of salt water, place it in a pan that is at least 6 inches deep and 12 inches across, and place a handful of freshly harvested Blue Lace within it. The Blue Lace will grow to fill the entire surface of the pan within two weeks.
Harvest all but a handful of Blue Lace when it is flowering. Dry it in a warm dark place on seasoned cedar boards. When it is totally dry, reduce to a powder and store in a dark-coloured, air-tight glass container.
Blue Lace has only one known magical use at this moment. Women (or men) can drink a tablespoon of this powder in a glass of water and for the next 24 hours will have an appearance of overwhelming beauty. It does not change the outward appearance at all; it is like a glamour is put on anyone who sees the person who has ingested the herb, that they perceive the drinker as overwhelmingly beautiful.
It has been used sometimes as a method of last resort by women who wish their beaus to 'come up to the mark' and propose, hence the alternative name of Bachelor's Downfall.