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The plants most commonly known as Forget-Me-Nots (Myosotis spp.) are small annual and perennial herbs in the Borage Family (Boraginaceae), with various species native to temperate North America, southern South America, Eurasia, Iceland, Sakhalin, Africa, New Guinea, Australia, Tasmania, and New Zealand. Most commonly cultivated species do well in full to part sun, with regular water and good drainage. Preferred soil pH can range from mildly acidic to mildly alkaline.
An Ericaceous Feed is a fertilizer formula that claims to be formulated for acid-loving plants. However, they do not usually contain any ingredients that would be harmful to other plants. You could use it as a fertilizer for your Forget-Me-Nots, though if it is not a complete fertilizer it may not be sufficient long term.
Typically, Forget-Me-Nots are grown outdoors in temperate climates and are usually not considered long-lived plants, though they will persist in gardens through reseeding. So far, what has your experience been with growing them as indoor plants?