Gymnocalycium Mihanovichii Black CactusThe Gymnocalycium Mihanovichii 'Black Widow' is a collector's cactus that's perfect for beginners. It's ideal for busy home or office settings, as it will add a unique visual with its velvety black ribs and white fluffy areoles. Easy to care for and thrives in full sun to partial shade with a well draining, gritty soil mix. During the warmer months, water generously and then allow the soil to dry out in between.