I just get a clove of garlic and peel it then crush it but not too much as it's that which blocks the nozzle sprayer. I use it mixed with water and spray through a fine mist sprayer onto anything that might be attractive to aphids, eg roses, carrots, broad beans, peas. I've only ever done it on roses and clematis but they were fine so I'm using it on the plot as well now but I don't know any results yet. Too early to tell :)
