Vitax Stay Wet Plus are water absorbent crystals with added fertilizer. Crystals retain and then release water. Controlled release fertilizer feeds for up to four months. These water absorbent crystals retain and release moisture, acting as a reservoir for plant roots. A two-in-one product, they also contain a controlled release fertilizer to feed plants for up to four months. They are ideal for hanging baskets and planters, and can be mixed with the compost at planting time.