The University of Connecticut originally bred dark opal basil, a type of sweet basil (Ocimum basilicum), in the 1950s. This annual ornamental herb sports aromatic dark purple-black leaves, which lend themselves to pasta, vegetable and soup dishes. Dark opal basil thrives in United States Department of Agriculture hardiness zones 2 to 10, where it reaches heights up to 24 inches and widths up to 12 inches.
Sweet Basil Dark Opal (Ocimum Basilicum Dark Opal) - Start these Sweet Basil seeds for both color as well as flavor. This Basil herb variety is called Dark Opal. The leaves have a clove-like spiciness flavor which is a little too strong for pesto but great for almost any basil dish, and it's especially good for vinegars and oils.
This old time favorite Dark Opal Sweet Basil herb has been delighting gardeners and foodies alike for decades now. Lots of people grow it for its decorative qualities, but it is a culinary wonder. Use its large glossy, purple leaves with large sliced tomatoes for fun contrast and a perfect flavor match that has been used since the turn of the last century! Dark Opal Basil grows best in full sun, but make sure it is fully protected from wind and the elements. Grow in a rich, well-drained, soil in full sun. Pinch out growing tips to encourage bushier plants and to delay flowering. Start Basil seeds indoors near a sunny window 6 weeks before transplanting to the garden after danger of last frost. Or, sow Sweet Basil herb seeds in garden in full sun when frost danger is over and ground is warm. Make shallow furrows and cover the herb seeds 1/4 inch with loose soil. Keep seed moist until germination.