With orders of $25 or more, Amazon offers the Miracle-Gro 48-Spike Indoor Plant Food for $2.24 with free shipping. That's tied with our February mention and is the lowest price we could find by a buck. Each spike feeds flowering and foliage houseplants for up to two months.

Note: This is part of the Amazon "add-on" program and can only be purchased with orders of $25 or more.