Thursday, February 20, 2014

My Tomatoes' Journey: Light (Part 3)

Apparently eight is the magic number for my seedlings this year, because I saw my first sprout today! It's teeny, tiny, but it's the real deal. Once your first seed germinates, remove the plastic wrap and get the tray into light. Do NOT wait for all the sprouts to poke through. For the next six months (and especially for the next six weeks), you need to ensure these plants get as much light as possible (ideally between 14 and 16 hours). In this post, I will share with you why plants need light as well as the ideal lighting conditions. 

Why do plants need light to grow? 

If you recall your basic science class in grade school, you may remember that plants need light to grow for a little process called photosynthesis. [For the record, I never enjoyed science. My last biology class was my freshman year of high school, and I took the easiest science courses in college to fulfill the basic requirements...we're talking "rocks for jocks" and an easy, easy physics class (like no trig involved). So, we won't dwell on the science, but I wanted to give you all a refresher course.]

Photosynthesis means using light (photo) to put things together (synthesis). Plants use light to "put together" food. In order to make food and grow, plants require carbon dioxide, sunlight, and water. Just as humans need to breath oxygen and drink water, plants "breath" in carbon dioxide through their pores (or stomata) and "drink" water through their roots. The third component is sunlight, which is soaked up through a plant's leaves. Cells make up leaves, and within the cells are chloroplasts. Chloroplasts make leaves green as well as convert carbon dioxide, sunlight, and water into sugar and oxygen. The plant uses the sugar for food and "exhales" the oxygen into the atmosphere. Here's my lighthearted attempt at a visual explanation:

So, light will ensure that the plants can make the necessary food to thrive and not become weak and die. Ipso facto...let's put our plants in a place they will get a lot of light.

What is the best light for my plants to grow? 

The more light the better. You could go all out and get some fluorescent lightbulbs and set up an indoor growing area, but without a garage or basement, I just don't have the extra space (or space out of the reach of little children) that I can commit for the next six to eight weeks. So, I will simply settle on the sun's natural rays (ho-hum). My plants will set up shop in a very well-lit room in my house until I transplant them outdoors. If possible, place them in an area with southern light exposure.

A few things to keep in mind:

  • Continue checking the trays daily for their moisture level. Only water (from the bottom of the tray) if the soil is not moist.
  • Turn the plants a quarter turn each day so they get even exposure to the sun. 
  • Try to find a location that has a fairly stable temperature (ranging from 60 to 75 degree F). Don't place the plants too close to a window sill as it can get cool at night. 

Apparently the fluorescent light set-up isn't that time or labor intensive, but I have not done this myself. If you want to use fluorescent lighting, here is a brief tutorial based upon a couple sources I've read (see below):

  1. Use a light fixture with two 40-watt cool white fluorescent bulbs, and space the tubes 3" to 4" apart. 
  2. Hang the light fixture above the plant trays and turn the light on 14 to 16 hours per day. (I've read to place the fixture from as close as 1" above the plants to up to 8" above the plants. Your guess is as good as mine.) 
  3. The temperature should be between 60 degrees and 75 degrees. 
  4. Check moisture level daily and water from the bottom when necessary. 
  5. Continue to raise the light fixture as the plants grow.

Check out my other posts on My Tomatoes' Journey.


McGrath, Mike. You Bet Your Garden Guide to: Growing Great Tomatoes. Fox Chapel Publishing. 2012. Pages 38-40. 

"Home Vegetable Gardening". North Carolina Cooperative Extension Service. College of Agriculture & Life Sciences. Department of Horticultural Science, NC State University. Prepared by Larry Bass, Extension Horticulture Specialist. 

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