Question
QUESTION: I started both pepper and tomato seeds about 3 weeks ago.  As they germinated I put them under shop lights.  Several of the tomato plants are starting to turn a purple color.  I used a seed start mix to plant them in.  Do they need some fertilizer or what.  I've just been using water.  Thanks for your advice!

ANSWER: Hi Connie,
Thanx for your question.  I grow thousands of tomato seedlings in a local greenhouse every year.  In fact, I've got over 5,000 out there right now and guess what?  Some of my babies turn a purplish color too.  It eventually goes away.  It seems to be a result of lots of light, cool temperatures and possibly a lack of certain nutrients.  In the past, I've started giving the seedlings a watered down mixture of fish emulsion in water (1/2 strength what is recommended on the jug of fish emulsion...).  Some tomato seedlings have a natural purplish tinge to them due to anthocyanins which are in the purple and darker colored tomatoes but usually not so prevalent on the leaves.  Like I said, the purple tint will eventually go away.  Some references have suggested soaking some nails in a just of water overnight and watering the plants with this as there may be an iron deficiency.  I really think it's a combination of light and temperature.  I've been doing this for years and once they get outside and the temps are warm, the purple is nowhere to be found.  I hope this helps.
Tom

---------- FOLLOW-UP ----------

QUESTION: Thanks for the good advice on the tomato plants.   One more question.  Is it possible to grow sweet potatoes in Montana?  If so what kind would you suggest and where could I find the seed potato?  I'm on the " warm edge of zone 3".  Thanks again!

Answer
Hi Connie,
Thanx for the additional information.  I couldn't find anything on growing sweet potatoes in Montana.  Generally, the growing season is too short although I have heard that there are some cultivars being grown as far north as Zone 5.  Sweet potatoes aren't grown from seed potatoes and are not in the same family as the so-called Irish potatoes which were developed from their progenitors which came from the Andes mountains of South America.  Irish potatoes are closely related to tomatoes, peppers and eggplant.  Sweet potatoes are a member of the morning glory family and are native to warm, tropical parts of the New World.  Sweet potatoes are propagated by slips.  You can grow your own slips by cutting a sweet potato in half and placing the cut part in a jar of water.  Keep the water clean by changing it periodically.  After a few weeks, sprouts will come out of the potato.  When the sprouts are 4 or 5 inches long you can cut them away from the potato and place them in a jar of water and they will root quickly.  Once the ground is warm (about 70癋) you can plant the slips and they will grow all over the place.  The climate must be warm and sunny.  Cool nights will do this plant in.  Contact the Montana State University Extension to see if they have some information on growing sweet potatotes.  Here's a link:

http://www.msuextension.org/

Here's an article from Mother Earth news that shows some cultivars in the range of 90-95 days for harvest.  Sweet potatoes are grown in Canada on the lake shore of Ontario but their climate believe-it-or-not, is a bit warmer than yours with a longer growing season.

http://www.motherearthnews.com/Organic-Gardening/2007-04-01/The-Sweetest-Potato.

I hope this helps.
Tom