Question
Gadsden,Alabama.
Have been attacked by Greenhorn worms on our tomato plants in pots on our deck. Going to pull plants as tomatoes done.Planning to plant cabbage & brussel sprouts in same pots. Do we need to do something to "clean" the dirt?? This is 1st year . Planning to grow garlic,shallots & potatoes in separate plastic containers w/ holes in bott.
  Have been told to plant our garlic 3" apart or 9 per sq ft. How deep a container do we need for garlic? Do they grow deep like potatoes? Will probably be "pickin' your brain as we are rookies. Thanks !!

Answer
Tomato hornworms are actually caterpillars that chew large holes in the leaves of tomatoes, eggplants, peppers, and potatoes.  Their young larvae are white but they eventually mature into a deep green that blends in with the foliage making them hard to detect.  You can control them by hand-picking them or using an organic control called BT (bacillus thuringiensis) commonly sold under the product name Dipel, Green Step, or MVP.  

BT is non-toxic to humans, pets, and the environment, and can be applied right up to the time you harvest. You can purchase these products at a local garden center or through an on-line catalog such as Gardens Alive or Planet Natural. I have attached a link to each for your convenience.

http://www.planetnatural.com/site/safer-dust.html

http://www.gardensalive.com/product.asp?pn=8797

I would recommend rotating your crop next year to prevent future generations of these insects from infesting next year抯 crop.  Also, be sure to thoroughly till the garden every fall to destroy pupae, the offspring of the tomato worm.

In regard to garlic, you are correct. Plant them in early fall or late winter with the root down, 3" below the soil surface and about 3" apart. The container should be at least 10" deep and filled with fertile potting soil. They do not not grow deep, but depending on the variety, can grow to the size of a tennis ball.

I hope this answered your question. Good luck, and please write again if I can ever provide assistance.

Regards,

Mike