In a word - no.

Customs and Excise Seeds and Plants Notice 701/38 quotes:
"The supply of plants grown to provide food for human or animal consumption, and the seeds or other means of propagation (spores, rhizomes etc) used to produce such plants, is zero-rated"
http://www.hmce.gov.uk/notices/701-38.htm

However, one notable exception (which might well be relevant in your case!! :-)
Customs and Excise Food Notice 701/14 quotes:
"Zero-rating applies to most food products, but there are exceptions. The exceptions, which are standard-rated, are supplies in the course of catering and supplies of certain specified items. These include ice cream, confectionery, chocolate biscuits, alcoholic drinks, soft drinks, crisps, salted or roasted nuts and home-brewing products."
(by which I mean the home-brewing products phrase!)
http://www.hmce.gov.uk/notices/701-14.htm