A couple of weeks ago I sowed three rows of carrots and hardly any of the seeds sprouted. My spotty row of carrots is pictured above—so disappointing! Luckily, there is still plenty of time to sow more.
Spotty germination happens for a few key reasons. The most common culprit when sowing small seeds like carrots is burying them too deeply. Each seed has a tiny food store inside. When exposed to the right temperature and moisture levels, seeds start to grow. However, if the seeds are buried under a deep layer of soil, they will use up their energy reserves before they can reach the soil surface and begin photosynthesizing.
I’m pretty sure that wasn’t the problem in my garden because I sowed the seeds and then covered them with a very fine layer of potting soil. I often use this technique when sowing small sees because it is easier to spread a thin layer of potting soil over a row. And unlike garden soil, potting mixes do not form a crusty layer that is hard for seeds to break through.
Spotty germination also occurs when newly planted seeds are watered inconsistently. Once seeds get wet, they need to stay damp until they sprout. Seeds that dry out in the interim often fail to germinate. I know this wasn’t a problem in my garden because it rained every day between when I planted and when the seeds that did sprout came up.
That narrows the problem down to the seed itself. The carrot seeds came from a free packet that my bank gave out on Earth Day. The package was labeled for 2012, but I suspect the seeds were not very high quality. Before I take the time to plant seed from this package again, I’m going to do a simple germination test.
To test seeds with uncertain viability, follow these simple steps:
1. Place 10 seeds between two layers of damp paper towel.
2. Slide the towel into a plastic bag, zip it three quarters of the way shut and stick it in a warm spot.
3. Keep the towels damp and check on the seeds daily. When the seeds begin to sprout, wait 3 more days. At the end of that time, count the number of seeds that have germinated. If six germinated you have a 60 percent germination rate. Likewise, if three germinated you have a 30 percent germination rate.
I suspect my seed will have less than a 50 percent germination rate. In the meantime I’m going to plant more carrots from a different pack of seeds!
Willi Galloway is the author of Grow Cook Eat: A Food Lover’s Guide to Vegetable Gardening, and she writes about organic vegetable gardening and seasonal cooking on her blog, DigginFood.