The acquisition means 151 will have access to Doff's metaldehyde production - shaking up the retail weed and pest control market.
Record metaldehyde slug killer sales buoyed the market this year. Chiltern Farm and Bayer are the only other metaldehyde manufacturers.
Doff, established in 1946, will be run as a standalone business by chairman Graham Whyatt and managing director Matt Jones, while 151 will rebrand and market Doff. 151 has eight brands and has plans to reach £100m turnover by 2015.
All Doff's existing product lines will be continued. Blue Diamond, Dobbies and Notcutts are among stockists but Doff has lost some business with B&Q and Wilkinson. Sinclair and STV have picked up some of the contracts.
151 Products managing director Richard Shonn said: "The two businesses have got vast synergies with our existing products and allow us to increase our market share at a time when demand is high."