- You will get 270 Seeds of Dark Opal Purple Basil Heirloom Culinary Herb Seeds. - Sunlight: Full Sun. - Life Cycle: Annual. - Watering: Medium. - Dark Opal Basil is a popular sweet basil with purple-black glossy foliage and pale pink flowers and a delicious aroma. - Dark Opal grows at a steady pace, it produces small to medium sized, tender leaves, reaching an overall height of between 12 to 18in tall and is slow to bolt. The dark purple leaves have a metallic green undertone or sheen in bright light and are flat and open compared to many other varieties. - Like many basil varieties, Dark Opal has a degree of licorice flavour, used as a culinary herb it gives both good flavour and attractive appearance. It can be used in fresh or dried form and can be frozen for later use. It works particularly well in salads and stir fry and is excellent when grown to micro-leaf stage for adding to salads and sandwiches. - Sowing: - It is vital that Basil is not exposed to the last spring frosts so if sowing outside be patient and sow in late March. Sow at any time if the plant is to be kept indoors. If sowing inside and planting outside, you can sow in late February. - Sow the seed thinly and if growing in pots sow enough for a few plants in each pot. Cover with 6mm of compost and firm gently. Basil seeds usually germinates in 7 to 14 days at temperatures around 70F. Once the seedlings have developed two pairs of true leaves, thin out the weakest seedlings, leaving each pots strongest.