Light as soon as they sprout
Need
Germinated seedlings require light immediately. Dim light makes the stem race upward
Fluorescents
Standard T-8, T-5, or CFLs can sit about 6 inches (15 cm) above the canopy
Stronger tubes
High-output T-5s and high-watt CFLs belong about a foot (30 cm) up
HID
Air-cooled 600w or 1000w HPS can sit about 1.5 to 3 feet (45 to 90 cm) up; uncooled lamps need about 3 to 4 feet (90 to 120 cm)
Move
You can germinate under HID or move seedlings under those lamps soon after they open
Watering without drowning
Stem rot
Fungus hits when mix stays too wet or roots cannot get air
Fine soil
Tight mixes hold water and starve oxygen. They need less frequent watering than a porous mix
Protect
Compost tea or a 0.5 percent peroxide solution helps limit fungal and bacterial attack
Feel
Water to keep moisture even, not to keep the cup sitting in a saucer
Dry mix is just as dangerous
No reserve
A seedling has almost no stored water. Wilt to lasting damage is a short clock
Leaves
Dry cells lose turgor and droop. Catch it and irrigate immediately
Roots and tops
Both the root and the canopy suffer when the medium goes dry
Check often
A small cup can dry between morning and evening under lamps or sun
Outdoor light caution
Season
Plant outdoors on a similar calendar to tomatoes and corn
Short nights
Early spring darkness can flip some varieties into flower too soon
Harsh sun
Late-spring and summer sun can wither a seedling that lived under indoor lamps
Harden
Start in shade or under screen and move to full sun over about five days