Monkshood belongs to the Aconitum genus and all contain aconite, which is a deadly poison if consumed!
Wolfsbane, the tallest monkshood, grows six to seven feet and produces creamy white or pale yellow flowers. There is also a species that is pale lavender.
The most garden-worthy monkshood, Aconitum nepellus, has brilliant blue flowers and also deep, deep purple ones that especially appeal to many gardeners. They bloom in high summer when blue flowers are not numerous in bed or border.
All aconites do best in partial shade with fairly moist, rich soil, but they will produce blooms even in full shade, though they will be fewer in number, and A. nepellus can grow up to five feet. Of course, plants in deep shade are often taller, as they are reaching for the light.
The purple-, blue-, and sometimes white-hooded flowers have a brooding aspect, and as the name suggests, are reminiscent of the hooded garb of monks. The low-growing winter aconite that is one of the very first flowers to bloom each spring, is a ground hugging species that produces bright yellow flowers.
The poisonous nature of these plants should be taken seriously, and indeed there are many other beautiful garden plants, such as rhododendron, azalea, and lobelia, (to name only a few), that are dangerous.
The moral of the story is that small children should be firmly told never to eat leaves or berries directly from the garden! There are simply hundreds of commonly grown plants that are toxic if eaten. However, the Aconitum species are so deadly that they are certainly not a good choice to plant in your yard while your children are young.