How to Fertilize snake's head iris?
Diluted iris feed every three to four weeks during spring bloom

snake's head iris · Iris tuberosa
Also known as: black widow; onion iris; widow iris
Plant tubers 10cm (4in) deep in autumn, in moderately fertile, sharply drained alkaline soil in full sun. Dry summers encourage flowering
Diluted iris feed every three to four weeks during spring bloom