Know-How Exchange : Strategy

Have tea tastings.
Tea parties (co-marketing with bakers)
Do tea "pairings" (what teas are best for what food, co-marketing with other vendors).

You may be able to get free publicity if you have something newsworthy. If not, pay for an advertisement.

Above comments very relevant. Go a step further--get published by citing the health benefits of tea vs. other beverages. Stats easy to find on the web, trade pubs, etc.
In competition, you have to ask:
- what makes you unique?
- what do you bring to the table (literally in this case) vs. your closest competitors?
- Research your product. Do informal questionnaires and use existing customer databases. What do they like/not like about your product? Believe it or not, many ppl don't do this.
- The pairings idea is excellent. Opens many new venues and co-marketing opportunities.
- Attend a Chamber of Commerce function--see if it's right for you. Many small / med biz owners there

A friend imports herbal supplements from Japan into America. She does a lot of sampling promotions in conjunction with the retailers. basically, they set up a table in the store, mix up the supplement, and offer samples to customers. She finds this to be very productive in growing sales at current stores.

Another option that stands out is to get out of your town, and grow into new towns. You said you have 30 stores in your city - why not duplicate that success with other cities as a means to grow?

I liked the shop promotion idea suggested by Peter. This way you could reach out to a large number of people. However, the flip side is that it is not very sharply focussed approach as not every shopper may be positively disposed towards Herbal Tea. It would be useful to combine this with a sharper approach.

It may be a good idea to target those places where you are most likely to get consumers for 'Healthy' product like yours.
I can think of fitness centres/gyms. Even spas and grooming salons where one is in frame of mind to indulge and nurture one's body.
You could tie-up with these outlets and merchandise your product in a 'low resistance format'- say a few free tea bags with a little booklet that carries information on Herbal tea including the beneficial aspects (anti-oxidants et al). It could be free or you could charge it minimally.
It's a mutually beneficial arrangement. For these outlets it could be a way to build loyalties with customers, for you it's sharply focussed sampling. Ensure the literature contains information on its availability and a call back number for queries.
In my view, focus on independent outlets (not chains of gyms etc) to start with as your success is more likely in these places where decision making will be faster and less procedure bound.

In addition, you should look out for some occasions where you could actually serve herbal tea (Controlled social gatherings/semi-formal business situations) but ensure complete supervision of the process as the brew must be served the way it should be. This is a good way to create a positive Word of Mouth. Have adequate product literature (take-ones) at the venue to generate further business at retail.