How to improve the germination of seeds

broccoli seedlings
broccoli seedlings

As cool, moist fall air banishes the hot, dry summer, my Arizona garden breathes a sigh of relief—and so do I. I’m busy at work, but my time in the garden is pleasant now.

Although my rows look empty from a distance, a close inspection reveals a bounty of tiny seedlings. My main fall crop is broccoli, accompanied by staggered plantings of beets, cabbage, lettuce, turnips, and other semi-frost-resistant veggies.

I planted the first row and four days later sowed another with the same mixture of seeds. Today, several weeks following the initial sowing, I stand between the rows with the startling realization that the seedlings planted most recently are at the same level of development and hardier than the earlier ones.

How can this be true? The seeds planted first should be farther along, right?

The plants in the first and second rows are the same size. The older seedlings are also spaced too far apart. A low germination rate left empty expanses that need to be replanted. The younger guys, though, present a continuous line of green leaves — too close together and must be thinned.

What happened?

It’s all about pre-germination.

Pre-germination (broccoli seeds)
Pre-germination (broccoli seeds)

I put dry seeds into the first row and then kept the earth moist while the tiny guys germinated. For the second planting, I soaked the seeds overnight in cool water (in the house) prior to placing them in the garden. This makes all of the difference in the world.

All types of seeds have a temperature range in which they will germinate. Broccoli prefers 70 degrees, but can tolerate a wider span. At some point, however, the smart guys realize the weather is either too hot or cold and they wait to enter the world. It’s a survival technique.

Seeds also cannot dry out during or shortly after germination.

When I plant my fall garden in the Arizona desert, I tend to sow seeds as soon as possible, pushing the edge of the season. The daily high temperatures are often still between 90 and 100 degrees. Additionally, it’s difficult to maintain a constant moisture level in my sandy soil, even though I have drip hoses and sprinkle twice a day with a garden hose.

The second row of broccoli performed better because it had help germinating.

Pre-germination (paper packet)
Pre-germination (paper packet)

There are a number of techniques that gardeners use to pre-germinate seeds, but my favorite is simply pre-soaking in cool water. I place the seeds on a paper towel and then fold it into a small square, enveloping the little tykes. I drop the wrapped gems into an open glass canning jar. (Any clean container will do.) Cool water from the faucet dribbles onto the packet until the paper is covered. Then the jar rests on the kitchen counter overnight.

Sometimes, when I plant the summer garden with melons or other veggies that prefer warmer germination temperatures, I place the jar on top of the refrigerator. Heat rises from the coils on the rear of the appliance until it hits the ceiling where it gently swirls down onto the top surface. I discovered this cozy environment while searching for a good place to let my yeast bread rise.

My broccoli seeds, however, prefer the cooler conditions of the kitchen counter top.

Pre-germination (cool water soak)
Pre-germination (cool water soak)

The next morning I take the jar out to the garden and open the packet on an empty pie tin, which accompanies me down the row as the planting progresses.

How deeply should the gems be placed into the earth? Generally speaking, seeds should be buried three times their diameter. So for my tiny broccoli balls, that’s not much. With an old spoon from the kitchen, I form a shallow trench, about ¼ inch deep.

The seeds go in next. It important to have extra ones, planted more thickly than recommended on the back of the packet. This allows for loss from bugs, birds, disease, or other mishaps. As the seedlings grow, they can be thinned on an ongoing basis to reach the proper spacing. Ideally, these broccoli seeds should be sown every inch or two, with a final spacing of 14-18 inches between adult plants.

My fingers drop tiny balls in a line. Then I return the soft soil to cover the small ditch, and gently pat it down.

The seeds are wet and need to stay that way, so the planting bed was watered the night before to produce a damp, but not muddy, environment.

When all of the beauties are planted, I sprinkle them down again. In fact, the soil must stay moist, but not wet, until the seedlings form their second set of leaves. Fortunately, with my sandy earth, I don’t generally worry about losing newly sown crops to ‘damping off,’ a disease that attacks the youngsters before or just after they emerge from the seed coat. Gardens with less drainage must balance the watering schedule carefully to avoid growth of dangerous fungus.

I once did an experiment with several different pre-germination techniques using tough okra seeds. I divided the large balls into five groups. Group One, the ‘control,’ was planted dry in the traditional manner. Groups Two and Three were pre-soaked in cool and hot water, respectively. I actually used a small carpenter’s hammer on Group Four to gently crack the seed coat. Group Five was planted in the garden in a fashion similar to the control, but I covered the garden bed with black plastic to warm the soil.

All experimental groups
the control group.

It turns out that the worst possible way to plant seeds is to use the traditional method – placing dry seeds in a dry garden bed and then watering them. Anything the gardener does to improve germination helps tremendously. By far, the easiest method is to pre-soak the beauties overnight in cool water as described.

My task today is to thin the crowded seedlings in the second row. Then I’ll soak a few broccoli seeds overnight to fill in the gaps in the first one.

I stand back to appreciate the garden’s beauty . . . but the seedlings are so small, that it makes the rows appear empty.

“Soon,” I say aloud.

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