by Amber

Windowsill Gardens Need No Grow Lights

Hmm… These lettuces disagree. They don’t look up to being a salad anytime soon. And that pitiful plant on the right is actually twice as old as the plant on the left.

This isn’t a report on a windowsill garden that failed. It is a windowsill garden plotted to be dismal before it was started… to prove a point. I’ve been planning this post for about 8 weeks. It’s the first in a series.

Inspired by artsy upcycled food cans, I saved a couple, washed them out, added drainage by knocking 8 holes in the bottoms with a big nail, and spray painted the outsides. While they were airing out to get rid of the paint fumes, it occurred to me that I needed a draining tray that would sit on the window tracks without the threat of toppling off. So off to the thrift store I went and scored a beat up aluminum ice cube tray for a quarter. (Never did get around to jazzing up the containers so they were more photogenic.)

So what’s wrong here?

They don’t need water. The light coming in this window is super bright, but the lettuces don’t have the strength to stand up like they should. It’s not a potting soil issue, and they have nutrients.

See how happy they are about life in this south-facing window? Due-south, mind you, not south-southwest, or south-southeast.  This window get much more than the ‘required’ 5 hours of direct sunlight a day. The perfect spot for a windowsill garden according to many a home magazine, book, newspaper article, and blogger.

Originally, I planted 3  cans on January 9th. After 2 weeks only one of the cans had sprouts. I was expecting less than 100% germination, but only 1 seed out of 6 germinated. So, I added a couple more to one can to see if it was the pelleted seed, or the cloudy skies that was the problem.

The problem here is a lack of sunshine.

There is a huge difference between sunlight and sunshine in terms of plant energy. Especially when the sun’s rays are weakened by a thick layer of gray clouds for weeks on end. In Michigan the average number of clear days in January is 3. While this windowsill garden in winter may be successful in some parts of the world without grow lights, as you can see it isn’t in the north.

The planter on the left was seeded almost 3 weeks later, but there is more sunshine in February, and it didn’t take them 2 weeks to sprout. Yes, there are 2 lettuces in that soup can, which helps to thicken up the top growth, but even then look how much larger the leaves are. They are fuller leaves too. These younger lettuces also didn’t stretch as much as the seeds sprouted in January. Note that the older plant didn’t recover from it’s light starvation a lot when the cloud cover lightened. While there are many cloudy days in February here, there are also some with almost cloudless skies.

Same Lettuce Grown Under LightsNow here’s lettuces from this same packet of seed getting started early for the outdoor garden last spring. These grow lights aren’t super power hungry. The plants are under high output T5 fluorescent which is plenty of sunshine for herbs and lettuce crops. By the way, under lights this seed sprouted in about 4 days.

The repurposed cans make great containers, and so does the junk shop ice tray/pot saucer. But if you’re going to enjoy fresh herbs and homegrown lettuce in the winter, you definitely do need a grow light where there are more cloudy days than sunny ones.

It’s just the way things work.

Now for the next 4 weeks I’m going to give them the cheap light treatment in addition to the sun. A shop clamp lamp with a huge 5000K CFL flood light bulb.

We’ll revisit their progress in late March.

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The garden played a starring role from spring through fall in the house Amber was raised in. She has decades of experience growing plants from seeds and cuttings in the plot and pots.