One of the things that many people don’t know is that water temperature and tomato seed starting is important but NOT in the way you might think.
Here’s the deal for what water temperatures and when to apply it to tomato seedlings.
This seedling is too lanky (not enough light) but you can see the four true leaves and this means it’s now watered with cold water.
p.s. when I transplant something like this, I put the entire long stem under the soil (the stem will root) leaving only an inch of stem above the soil line.
#1 Starting Seeds
Water temps for starting seeds should be luke-warm or baby-bottle temperatures. Not warm enough to burn or be uncomfortable but not cold either.
#2 But as soon as the seed germinates, then the regime changes.
The water can go to room temperature immediately after germinating and stay that way until the seedling has 4 true leaves.
#3 When the plant has four true leaves, then stage three kicks in –
You use cold water on the tomato transplants.
By cold I mean water that is between 40-50 F. (measure it with a good thermometer to get a sense or what this is) This encourages the seedling to stay short and compact if all other variables are right (high light levels mostly).
A hardy vegetable seedling produced this way does better when transplanted into the garden – much lower shock and faster growth. I used this technique and a temperature technique (I’ll detail that in another post) to produce superior commercial and retail transplants for my customers. My commercial customers would always trial my plants against other producers and mine consistently won for early fruiting and total yield (they tested them because mine were always more expensive to buy but produced more so they made money in the long run but wanted to keep checking)
If you want a recent research report (this kicked my own tests and results back in to my memory to share with you) you can hunt up and read
Reference: Y.-W. Sun, J.-J. Chen, W.-N. Chang, M.-J. Tseng, and F.-S. Wu (Dept. of Biology, Virginia Commonwealth Uni- versity, 1000 W. Cary St., Richmond, VA 23284-2012), “Irrigation with 5°C Water and Paclobutrazol Promotes Seedling Growth in Tomato (Solanum lycopersicon),” Journal of Horticultural Science & Biotechnology 85(4), July 2010, 305-311. (Headley Brothers Ltd., The Invicta Press, Ashford, Kent, UNITED KING- DOM.)
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