When do I switch to bloom nutrients?

The plants keep stretching for the first 1–2 weeks of 12/12, so many growers keep some grow feed during the stretch and then move to bloom. CANNA, for instance, suggests changing when flowers begin to develop, normally 1–3 weeks after the light switch. In practice you slide from grow to bloom over a feed or two rather than switching at once.

Bloom feeds are lower in nitrogen and higher in phosphorus and potassium. Open the chart of the brand you use, there is one for each line in our nutrients.