Grows around edge of tray but not in the middle -- Likely the soil was too wet. The edges of the tray tend to dry out first. Water more around the edges than in the middle.
Damping off - Seeds germinate, seedlings appear, & then die -- This is caused by 4 things: a fungus in the soil, extra moisture in the soil (activates the fungus), temperatures above 68F, too much nitrogen in the soil. To treat: use clean trays (washed with Dawn dish soap and then in 10% bleach solution), don't add any fertilizer, and don't over-water the microgreens. Improve the air circulation by putting a fan near the microgreens.
Seeds not germinating or plants not growing -- Something in the plant environment is not correct – is there 40- 55% humidity, a room temperature of 65-78ºF, enough water, or enough light? Is the pH of your water correct? Microgreens prefer a pH of 6.0 to 6.7. The pH of your water can be changed by using baking soda or white vinegar.
Plants are laying down -- The soil is too dry or the plants were not taken out of the blackout dome soon enough.
White mold (Sclerotinia) is growing on the soil surface – Is it mold or root hairs? Roots hairs may look like mold. The root hairs will be coming out from the root thread. White mold will look like a spider’s web. Mold is caused by high humidity (should be 50% or less) or not enough air circulation. To treat the mold, spray the surface with 1 quart of water mixed with 1 Tbsp of 3% Hydrogen Peroxide. Depending on the cause, this could also be treated by spraying the soil surface with Baking Soda water (1 teaspoon Baking Soda per quart water) however be aware that this will cause the soil to become more Alkalined.
Botrytis (a grey mold on the green plant stem) - Is caused by the seeds not being rinsed after they are soaked. It can be treated by spraying plants with [Per gallon of water: 1 Tbsp baking soda & 1/2 Tbsp dawn dish soap] or spray lightly with mouthwash (the same kind as used by humans).
Uneven growth -- Seeds were not evenly disbursed when planted, or watered too heavily.
Sections of Rot in the Crop - This could be caused by a number of things but most likely by watering with water that is too alkalined. Adding a bit of white vinegar or lemon juice to your water would make it more acidic. Another possible reason is the seeds were sown to thick.
Dry Rot Fungus - a decay of the stem starting at the base and/or the root.
Grey mold (Botrytis) on the leaves -This is a fungus that likes cold wet conditions. Increase the air circulation and keep the temperature above 65F.
Black leaf spot (Cercospora) - This fungus is caused by wet foliage. Increase air flow and bottom water the microgreens instead of top watering. This could also be treated by spraying the soil surface with Baking Soda water (1 teaspoon Baking Soda per quart water) however be aware that this will cause the soil to become more Alkalined.
Yellow leggy Microgreens - This is a normal condition when the Microgreens are in the blackout dome. When put under a grow light they will quickly turn green.
Yellowing leaves (Chlorosis) - If the leaves are yellow after they have been exposed to sufficient light this often means there is an iron deficiency - that the plants can't access the iron in the soil because the soil is too wet.
Leaf curling - This is a sign of the microgreens needing magnesium sulfate. To treat mix 2T of plain Epson salt in a gallon of hot water. One the water is cooled, use it to spray the Microgreens.
Microgreen Stems are weak – The three most common reasons for this are: seeds where not put under weight, the plants were not bottom watered, or the humidity is too high.
Microgreens Taste Bitter -- If they were picked too late (after the 2nd two leaves appear), they will taste bitter. Pick when you see the very first sign of these leaves. An exception to this is peas which should be harvested when they are 4" tall. Lettuce, Cilantro & Basil can also be grown longer.