Posted on 24 May 2008 by

TC Reader Question: Should I not use potting mixes with fertilizer when starting tomato seeds?

By Michelle Fabio

One of our readers recently received seeds from Totally Tomatoes and with them came a note: “We don’t recommend using potting mixes with fertilizer for starting seeds.”

The reader is wondering why Totally Tomatoes make this recommendation.

The truth is that seedlings really don’t need fertilizer until they develop their first set of leaves, and indeed, starting with high amounts of fertilizer can actually cause more harm than good to your tomato plants.

Inorganic fertilizers, in particular, have been known to “burn” seedlings as their nutrients can be released too quickly, inhibiting germination.

Also, if you have leggy tomato plants, too much fertilizer, namely high amounts of nitrogen, just may be the culprit.

And while we’re talking about fertilizer, note that many soil starting mixes do contain a low amount that will nourish your seeds until they get their first leaves. At that time, you should introduce fertilizer gradually to your plants; a diluted solution is a good idea for a while.

For more information on starting seeds in general, including a convincing argument as to why you should always choose organic fertilizer, see Arzeena Hamir’s article Prepare to Start Seeds on the always informative

What is your experience with seeds and fertilizer?

One Response to “TC Reader Question: Should I not use potting mixes with fertilizer when starting tomato seeds?”

  1. Ryan, AL Says:

    I used some inorganic potting soil with my heirlooms and the germination rate was around 60% with no consistent problems from germination to transplant. There were a couple that looked completely stunted (about one in eight) but it’s too early to know how those are going to turn out. The others are fine so far.

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