Shepherd's purse due to the growth of different environments, in order to adapt to the relatively more vicious living environment, shepherd's purse in the growth process of genetic changes gradually, so it will look a little different.

Some of the caper is purple also because some varieties are not the same, is after subsequent improvement of the varieties, caper nutrition and it is what color has no absolute relationship.

Species differences:

While the caper and the water caper are called caper, the form is similar, and are eaten, but strictly speaking, the two are not the same plant, first of all, two kinds of caper belong to the cruciferous family, but the caper belongs to the caper genus, water caper is also called the large root caper, belongs to the genus nasturtium [hǎn] cabbage.

Generally in the field, the wilderness or the roadside can be seen these two kinds of caper, but water caper prefer to grow in a more humid environment, such as the river, creek side, and the more humid place the more vigorous.

The above content reference? Baidu Encyclopedia - Capsicum (Cruciferae Capsicum)