It is a green flower in its initial stages, identical to Roses, Dandelions, and all other flowers. Before it fully matures, it may look like a Tulip. Once mature, the flowers turn light purple. Venomilia is nearly identical to Tulip, but the Tulip flower is a darker purple.
To harvest the plant you can right-click it. Left-clicking will harvest the plant as well as destroy it. Like Tulips, harvesting Venomilia may yield purple dye and sometimes grin powder. When harvesting while destroying, Venomilia may also produce Venomilia Seed Bags. Venomila is a poisonous plant which promotes weed growth and may poison those who touch it if the stem has purple buds on it. The harvest of the plant is determined by the plant's Gain statistic.
A good way to increase the amount of Purple Dye it drops, how fast it grows and how resistant to trampling it is, is to cross breed Venomilia with Venomilia as this has the highest chance of getting a Venomilia. Collect the seed bags, scan them through a Cropnalyzer and then cross breed the two Venomilia seed bags that have the highest statistics with each other as this will often yield even higher stats. Then you can continuously breed the plants with higher stats together until you are satisfied. A more in-depth view of crop stats can be found on the Cross Breeding and GGRpages. The stats are referred to as Growth, Gain and Resistance. Recommended cross-breeding combos: Tulip + Tulip, Any two flowers.
Recommended cross-breeding combinations: Nether Wart + Reed. In extreme(ly rare) cases from Cocoa + Reed.
Venomilia Growth Stages: