Light for Microgreens: Your Windowsill
Can you grow fresh salad greens full of flavor on your windowsill? Many people would love to have locally grown leafy greens available to them every week, and just can’t because they aren’t available. Some just don’t have the money to afford local produce.
Direction matters (sometimes)
All window sills are not created equally. How much light your window gets can vary greatly due to the direction it points, the type of window it is, or if something blocks the sun from getting to it. The direction the window faces is probably the biggest factor for most people, so let’s take a look at the options.
North facing: Since the sun follows a southern east-to-west track, which is even more southerly in the winter, a north-facing window will have the least amount of light.
East facing: This window will get direct morning light, so better than a north-facing.
West facing: This window will get afternoon sun when it is at its strongest.
South facing: This window should see sun almost all day and is your best chance for growing healthy plants.
Watch the temperature
Temperatures in a windowsill can vary more than outside temperatures. Windows can act like a magnifying glass for the sun and burn your young seedlings. A poorly insulated window can also be very cold at night. Optimally, you will need above 70 degrees to germinate your seeds, and between 60 and 70 degrees after that.
Your microgreens can stand some variance in temperatures, but whatever you can do to keep the temperatures even will help. Just make sure to not limit the amount of light that gets to them if possible. Look for poor germination rates because of the colder temperatures in the winter, and drying/wilting because of the hotter temperatures in the summer.
I have no windows on the east or west side of my house. I have a couple of south-facing windows that aren’t blocked by a tree in the wintertime when the tree doesn’t have any leaves. I also have a couple of north-facing windows that are not blocked at any time of the year, but terrible in terms of light simply because they are north-facing.
My houseplants have always struggled, but not so with microgreens. If your growing microgreens only to the seed-leaf stage, then having lots of light is not necessarily needed. Sometimes, less light can even be a good thing. Let’s take a look.
Kale worked well in both the south-facing and north-facing windows. I started both kits with 10ML of seed. Put them in the window immediately. I took the clear cover off as soon as germination occurred.
Harvesting yielded a surprise. The Kale in the north-facing window produced more than the Kale in the south-facing window.
South-facing: 2.20 ounces
North-facing: 2.35 ounces
Withholding light makes microgreens stretch for more light, netting you more growth. You would not want to do this if these seeds were for your garden. A leggy plant is weak and will fall over in a heavy wind or rain. But for microgreens and their short growth period, these features work in your favor. Commercial growers will sometimes withhold light at start the growth period to get them taller and so they have a better taste.
One thing I will change is to put holes in the windowsill kits and use the bottom-up watering method. I watered almost 24 hours before harvesting, and even with that length of time the microgreens were still damp. Water doesn’t help microgreens stay fresh when stored, so I prefer to harvest them while dry.
I put 90ML of field peas in warm water for 12 hours. Then I put them in a windowsill kit in a south-facing window of my house. I took the humidity cover off as soon as germination occurred, which I think was a bit too soon because I had several peas that did not germinate.
North-facing window: 1 ounce
Fluorescent Light: 2.20 ounces
As you can see, I could get double the amount from a grow light. The window-grown peas looked leggy and weak, and overall didn’t turn out that well. This doesn’t mean peas won’t work in your windowsill. They just need brighter light than I could give them.