How does it know a weed from a plant?

Tertill Weeding Robot uses height to determine if something is a weed or a plant. That's why it needs to be placed in a weed-free garden to start - either at the beginning of the season or right after you have weeded. If a plant is tall enough to touch the robots sensors, Tertill turns away. Plants that can pass under the robot are assumed to be weeds and get whacked down with the onboard string trimmer. Included metal guards keep young plants safe until they grow taller.

Does it pull the weeds out?
Tertill Weeding robot controls weeds in two ways. First, its specially designed wheels churn up the top layer of dirt disrupting many weed seeds from ever growing. If any weeds do manage to sprout, the robot cuts it down with its onboard string trimmer. The whacked weeds are small and fall to the ground, shrivel up and decompose - returning the nutrients back to the soil.
Won't the weeds just grow back?
 A whacked weed may sprout again, but Tertill will keep coming back cutting it down until it runs out of energy and dies. Sorry. (Not sorry)
Why does Tertill stop so much?
Like its namesake the Tertill Weeding Robot basks in the sun for most of the day. When it has enough battery power, it sets off patrolling for about 2-5 minutes before stopping again to recharge, When added together these short intervals add up to about 1-2 hours a day - which is enough to maintain a 200 square foot garden.
Do I need to charge my Tertill?
Tertill the Weeding robot is solar powered, so it never needs to be charged. It does have a USB port on its belly if you want to charge it, say after it has been stored all winter.
How many Tertills do I need for my garden?
Each Tertill Weeding Robot can maintain up to 200 square feet  which is the size of a 10 ft. x 20 ft. garden. If you have a larger garden, you can section off 200 square feet or consider getting more than one robot. They work well together. 
Does Tertill ever get stuck?
Tertill Weeding Robot has 4-wheel drive, a low round body, and slanted wheel which help it navigate around the every-changing garden terrain, but it can still get stuck. When you first put Tertill in the garden it is best to check on the little fella every couple of days to make sure there isn't a corner or slope that traps it. If Tertill is stuck, just eliminate or block off whatever trapped it, place Tertill back in the garden and press the button to hear the charge tune to make sure the robot is not in standby mode.
What does a purple LED mean?
If you see a purple LED and are having difficulty either turning Tertill off or getting it to patrol again, contact Technical Support at support@tertill.com or call +1 (833) 837-8455  (Just remember 833 TERTILL).