Question
I am starting tomatoe seeds in flats as I do every year.This year however I have some yellowing leaves some are upturning and appear slightly burnt on some tips.I am using miracle growpotting soil same as every year.I am growing marglobe,betterboy,and sweet100.Betterboy is fine others aren't what is going on?

Answer
Yellow leaves are almost always a sign of poor drainage or too much water. Some varieties handle it better than others. What happens is that the excess water depletes the soil of nutrients and minerals, depriving the plant of what it needs to maintain green foliage and strong growth. The good news is that the problem always corrects itself once the watering is more consistent. Always be sure to allow the soil to dry out between waterings.

You also mentioned slightly burnt tips., This is usually caused by the roots burning. Burning of the roots can be caused by excess nitrogen applications or by salt in the soil. Many of the synthetic fertilizers have salt added as an inert ingredient. That is why I always recommend using organic fertilizers on seedlings. They are less harsh and just as effective. They are also more balanced, with equal parts of nitrogen, phosphorus, and potassium. The latter two are essential for fruit-bearing plants, such as tomatoes, while fertilizers high in nitrogen are recommended for leafy vegetables such as lettuce. Once the seedling matures, regular fertilizers can be applied at their recommended rates.

I hope this answered your question. Please write again if I can ever be of assistance.

Regards,

Mike