Quantity   Component name
1 × Adafruit Trinket 3.3v http://www.adafruit.com/products/1500
1 × Mini breadboard http://www.adafruit.com/products/65
1 × Steel/Nickel Nails Bear in mind that the nails will eventually dissolve away, and if they are galvanized they may leak chromium into the soil. Which would be bad.
1 × 4.7k Ohm Resistor
1 × 3.3k Ohm Resistor
1 × 100 Ohm Resistor
1 × Big-ish LED
1 × Jumper Wires