Water the plant before inserting the vial into the soil. Snip off the top of the vial and insert the nozzle into the soil at a slight angle, away from the plant. Because of variations in soil type and density, the rate of flow of the feed from the vial can vary greatly. On average the vial will last 15 days, but may empty more quickly in some circumstances. The plant will still have received enough nutrition for 15 days even if the vial empties sooner.