So, how are you going to mark those plants? I think you'll have a hard time choosing because there are some great ideas out there that you can purchase or make at home for just pennies.
(Each photo has a link to what I believe is the original blog, Etsy shop, or website and it's tutorial if provided).
Custom Flatware Markers from Beach House Living
Do It Yourself Stamped Flatware from Bunny Hill Designs
Hand Painted & Decoupaged Markers from Homespun Sprout
Recycled & Stamped Can Lid Markers by Pin & Paper
Juice Lid Markers by Still Parenting
Aluminum Duct Tape Marker from Aunt Peaches
Painted Rocks from Whimsey Love
Wine Cork Marker from Eat Drink Better
Clothespin Plant Marker from Glue & Glitter
Twig Markers from Storage Glee
Seed Packet & Jar from Martha Stewart
Keep in mind that whatever plant marker you use, it needs to be water proof. Even if you're using a drip system, water happens. I have used a Sharpie in the past, but it's not quite as water proof as you might think. So last year I switched to the Garden Pen sold by Johnny's Select Seeds and it won hands down.
For the stamped flatware, you'll find that Harbor Freight Tools carries an inexpensive set for under $15. It's a nice size and includes numbers.
So... which one would you choose?