• Mulching is an important practice to maintain moisture levels and prevent weed growth throughout the year. It is important that plants at all times have a thick layer of mulch around them. • Blackberries need a lot of water both when growing and while they are maturing. You should stick to a watering schedule of one inch for your plants in hot weather. • You should feed your blackberry plants in the spring using an all-purpose fertilizer such as 10-10-10 or 16-16-8.