Fruiting plants in particular require at least twelve hours of bright light, which may be difficult to obtain in Michigan winters. Annuals are more specific in their light requirements. Short day plants flower when there is only 10 to 12 hours of light and will not flower with excess light. Long day plants require at least 14, and preferably 18, hours of light to flower. These plants are best grown under a fluorescent light.
Indeterminate plants have minimal photoperiodic response.
This category includes most vegetables. Most leafy and root crop vegetables prosper in cool temperatures. Highs of 60 to 65 degrees Fahrenheit with lows at night ranging all the way down to 40 degrees Fahrenheit are acceptable. Fruiting vegetables and most annuals require warm temperatures. For example, tomatoes will not set fruit unless nighttime temperatures are between 60 and 70 degrees Fahrenheit, with ideal daytime temperatures at about 80.