Jobe's® Fertilizer Spikes Potted Plant & Hanging Basket 6-18-6.18pk Resealable Pouch. Convenient and easy to use, Jobe’s fertilizer spikes provide nutrition underground – where plant roots can use it. Just insert spikes around plants and the slow-release formula feeds plants for up to eight weeks. Plus, spikes ensure that nutrients aren’t washed away like surface applied fertilizers. The specially formulated, premeasured spikes make for a fast, easy and mess-free fertilizing experience.