Jardiniere is a French cooking term meaning to cut a vegetable into thickish batons.
This is the size of vegetables commonly used in frozen vegetable mixes.
Peel and wash the vegetable, then regularize its shape into a rectangle or square by topping and tailing it and squaring off the sides. Cut the vegetables into pieces 10 cm (4 inches) long. Then cut these pieces into batons with a width of anywhere from 4 mm to 10 mm wide (⅛th inch to .4 inches), then cut the batons down to their final width of anywhere from 2 to 5 mm.