Sometimes I collect seeds from my flowers in the fall and plant them in the spring. Some sprout and some don’t. What am I doing wrong? SB

Seed dormancy is how nature sets the germination clock so that seeds germinate when the conditions are best for success. For example, many of us have dogwoods in our landscapes. Dogwoods produce seeds in the fall, but fall is not the best time for these seeds to germinate and grow. Because of that, dogwood seeds go through a process known as “scarification” as they over-winter to make them ready to germinate in the spring. There are a couple of processes that prepare seeds in nature for germination. Let’s talk about those.

There are a variety of plants whose seeds need to go through the process of scarification to prepare them for spring germination such as hawthorns, golden rain trees, wisteria, dogwood, camellia, Kentucky coffee tree, persimmon, and redbuds, among others. Seeds that must undergo scarification typically have a hard seed coat that needs to be softened (if you will) before the seed will germinate. There are a couple of ways this happens in nature.

When seeds of these plants are produced in the fall, they drop to the ground. Freezing temperatures can soften the seed coat as can microbial activities in the soil over the winter. Some seeds undergo scarification as they pass through the digestive systems of animals. Either way something must act on the seeds to soften their seed coats so that they are ready to germinate in the spring.

Professional growers attempt to replicate scarification using sulfuric acid while many home growers use vinegar. I have never attempted either and probably won’t, choosing instead to purchase plants from a nursery, but that’s just me.

Stratification is another process nature uses to prepare seeds for germination. Seeds from plants that require stratification include veronica, lavender, phlox, rudbeckia, delphinium, asclepias (milkweed), and penstemon, among others. Seeds from these plants need to go through a period of cold before they will germinate successfully. This is why many gardeners gather seeds from their milkweeds to be kept in the refrigerator until spring planting. There are a variety of recommendations to accomplish stratification for various plants, but all involve a “chill” period in the refrigerator.

OSU recommends soaking seeds in need of stratification for 12 to 24 hours in water at room temperature, then storing them for two to six months in the refrigerator along with a damp paper towel. Stratified seeds should be planted as soon as they are removed from the refrigerator.

In both processes, all we are doing is mimicking what happens in nature that enables these seeds to germinate.

Fruit plants of various kinds require what is called a chill period to produce their fruit. The chill period is the number of hours below 45 degrees these plants need to produce fruit in the spring, and different varieties require a different number of chill hours. As you can imagine, chill hours vary across the state. For example, in the Tulsa area, blueberry varieties that do well here are those that require around 800 chill hours per season while varieties that can be grown in the southern part of the state might only need 150 to 600 chill hours.

Peaches are another one that are dependent on chill periods. Warmer winters that don’t meet the chill hours requirement can reduce production while nice cold winters (yes, I said nice cold winters) can increase production. While a lot of us are not fond of cold winters, they are necessary for us to have the delicious fruits we all enjoy.

One might assume that a fruit variety with a lower chill hour requirement would be the best choice for our area. But varieties with low chill hour requirements are more easily damaged by fluctuating spring temperatures. For example: if you have a fruit variety that has a low chill hour requirement, this means that when we first begin to experience warmer days, they will be ready to start blooming. The downside to this is that a late freeze can take out all the buds, greatly reducing the crop. On the other hand, a variety that requires a greater number of chill hours won’t have met its quota for chill hours, and therefore it probably won’t be tricked into blooming early and then getting damaged by a freeze.

Many types of garden vegetable seeds prepare for germination through what is called “shallow” dormancy. This type of shallow dormancy is overcome by allowing these seeds to go through a dry period. You have probably noticed that seeds you purchase in packets are always packed in dry containers. No special treatments beyond this are required.

We have a link to information on where you can learn more about plant propagation in the Lawn and Garden Help section of our website (www.tulsamastergardeners.org).

Once you become aware of all that goes in to producing plants and produce successfully, it’s easy to be amazed we can grow anything at all. But we can and we do so maybe we just need to “chill” and enjoy it. See you in the garden!

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701, dropping by our Diagnostic Center at 4116 E. 15th Street, or by emailing us at mg@tulsamastergardeners.org.

Milkweed seed - Steven Katovich, Bugwood.org