I bet that gives you warmer soil much quicker!

You should paint the outside of them (or have some bored kids do it lol!) or write the name of what you've sowed in them.

I bet you now don't have to worry about weeds growing amongst them, damage from moles & a few other animals, you don't have to worry about everything wash away with heavy rain.

Tires can even be used to create retaining walls to stabilize an earth bank. When using them for this purpose, begin by laying a level course of tires. Fill these tires completely with sand, soil, or gravel. Try to eliminate any holes or pockets in the tires that might provide a haven to vermin like mice or rats. Atop the first course of filled tires, add another row, positioning them one-quarter to one-third of the way back on the first course. This will give the wall some slope and add stability. Also, place the tires with staggered joints, that is, in bricklayer-fashion.