What causes yellowing leaves on sweet million tomato plants?

Question

I am growing two sweet million plants in my greenhouse. I obtained the seedlings from a commercial greenhouse and transplanted them into a big container. I noticed that the leaves are turning yellow with the older leaves yellowing first. They don't seem to have wilt as the leaves aren't drooping or curled, and I haven't noticed any dark spots on the leaves. The blossoms are drying up and now one of my plants only have a few leaves that are turning yellow. I've never grown tomatoes before and I am a new gardener. Could it be anything to do with the temperature in the greenhouse or the amount of direct sunlight the plant is receiving (my greenhouse is made of opaque plastic? I live in a cooler climate. I don't think I am overwatering as the soil is just moist/damp but not wet. Please help!

Answer 1

This may be a simple case of over watering. It is the MOST frequent cause of death in household plants. Most new gardeners and plant owners tend to love their plants to death. Roots need to breath as much as the leaves do.

A simple rule for watering is to feel the soil about an inch or two below the surface. If you feel moisture the plant does too, so it needs no water. I would suggest this method until you have worked out a schedule for watering.

If you don't trust your judgment on what it should feel like there are literally hundreds of gizmos and gimics out there to help you test. Simply go to any garden shop or (gasp I can't believe I am saying this) Wal Mart or Home Depot and ask for something that test for soil moisture.