Regional Gardening Reports :: National Gardening Association

In the Garden:
New England
February, 2011
Regional Report

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Nick the ends of morning glory seeds with a sharp razor blade, a technique called scarification, to condition them to absorb moisture so they can start the process of germination. Then soak the scarified seeds overnight in tepid water before planting.

The Ins and Outs of Seed Sprouting

Remember when you were a kid and your mother told you not to swallow watermelon seeds or they might grow in your tummy? You probably thought she was joking, but it turns out, she may not have been that far off! Doctors in Boston recently removed a pea that had sprouted inside the lung of a 75 year old man. At first they thought he was suffering from lung cancer but eventually discovered that his symptoms stemmed from a half inch long sprouted pea seedling that grew from a pea he had accidentally inhaled! While aspirating foreign objects into the lungs is a familiar, if not frequent, problem encountered by doctors, finding sprouting plants is much more unusual, although one doctor pointed out that the warm, moist interior of a lung affords perfect conditions for germination. A couple of years ago, Russian doctors removed a 5-centimeter long, little fir tree seedling, needles and all, from the lung of a 28 year old man who they think must have inhaled a seed or bud by mistake. (Note to Mom: the acids in our stomachs make it unlikely that any seeds reaching there will grow.)

For those of you who are planning on making your seed sprouting an "out of body" experience this spring, let's take a look at what more conventionally planted seeds need to begin the process of germination. All seeds are in a state of suspended animation, waiting for the right set of conditions to awaken and begin to sprout. Seeds contain chemical and physical inhibitors that keep them from germinating when the environment isn't suitable. Once the seed receives the proper "conditioning" that destroys these inhibitors, it "knows" that it's safe to start on the journey to becoming a plant. Understanding what conditioning particular seeds need sets us on the path to seed starting success.

All seeds need moisture to germinate. So why don't mature seeds on a marigold begin to sprout while still attached to the seed head? The seeds of many of our vegetable garden plants, such as tomatoes, zucchini, and cucumbers, and warm season annual flowers like zinnias and marigolds, need to be exposed to a certain amount of drying before they are ready to absorb water again and germinate. This drying conditioning keeps seeds from sprouting prematurely while still attached to the flower head or even inside the fruit itself. By the time we purchase commercially sold seeds of these plants, this conditioning has been met.

Some seeds have a very hard seed coat that in nature is broken in a variety of ways that assures that the seed germinates under the proper conditions. Alternate freezing and thawing temperatures, extreme heat from a fire, passing through the digestive system of an animal are all ways in which a hard seed coat can be breached to allow moisture in. We can reproduce this conditioning with a procedure called scarification, which is simply nicking, scraping or cutting through the seed coat. For example, you can cut off the pointed end of a morning glory seed with a sharp razor blade or scrape the seeds across a piece of sand paper. If you have a lot of seeds to scarify, put them in a jar with some coarse sand and shake vigorously.

Sometimes soaking is enough to soften the seed coat to speed germination. Soaking can also speed germination by removing chemical inhibitors from the seed coat. Soak parsley seeds for 24 to 48 hours before planting, pouring off the water and replacing it with fresh several times, discarding the leached out inhibitors in the process.

When we think of planting seeds, what springs to mind is usually a picture of tucking seeds into the soil. And while some seeds do need the darkness of a soil covering for germination, most will germinate in light or dark, though the covering of soil helps to keep them moist. But some do require exposure to light to break down inhibitors in the seed coat. Lobelia, impatiens, and ageratum are seeds that need light for germination; simply press them on to the surface of the germinating medium, rather than burying them.

Certain seeds, usually of perennials, trees, and shrubs from temperate climates, need to be exposed to a period of cool temperatures before they're ready to germinate. This prevents them from sprouting prematurely when the weather is too cold for continued growth. In nature, these conditions are provided by normal seasonal changes. When gardeners mimic this process, it's called stratification. Seeds are given a period of moist cold (40-45 degrees F) for about 6 weeks to duplicate going through a cold winter; a refrigerator easily provides the appropriate "winter" chill.

Once seeds have been conditioned, most need warmth in addition to moisture to germinate well. The majority of the seeds we start early indoors appreciate bottom heat from a seedling heat mat or the top the refrigerator that keeps the germinating mix between 70 to 80 degrees F. But be sure to check the instructions on the seed packet for the specific requirements of plants you're starting. And for Pete's sake, don't inhale any seeds!

Final note to Mom: Those watermelon seeds are actually edible! According to the National Watermelon Promotion Board, the seeds are rich in fats and protein and make a tasty snack. Put them in a skillet with a small amount of water and some salt, cook until the water evaporates, then enjoy!

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