Growing Flowering Dogwood Trees
By Jeff Edwards
Flowering Dogwood trees are easily grown from seed, with the caveat that the overwhelming majority of seedlings that sprout will be White Flowering Dogwood, or Cornus Florida. It makes no difference if the seeds are collected from a White Dogwood or a Pink Dogwood, the seedlings are more than likely to be of the white variety.
Dogwood trees start producing seeds immediately after the petals fall from the flowers. The process is slow and literally takes all summer. When the seeds begin to ripen red in the late summer, it indicates that they are almost mature. Be careful not to pick them too early though, as the embryo will not be fully developed, and the seed will not be viable. When they are completely developed, the seeds will start to fall from the tree, and only at that time can you begin to safely pick them. Ripe seeds should be able to be easily removed. If they don't pop right out as you grab them, it indicates that they are not quite ready, so it's best to allow them another week or two for further ripening. Birds, chipmunks and other animals love to eat the seeds, especially those that have fallen to the ground, so be sure to pick them before they do.
After the seeds are picked, allow them to sit out for a week, maybe ten days, until the pulp begins to soften. At this point, soak them in a pail of plain water to help further soften the pulp. While they're still in the water, squeeze them between your fingers to manually remove the pulp from around the seeds. After you have separated the pulp, add more water to the pail until it overflows, while allowing the water to slowly flow over the edge. Ideally, you want to do this in a sink or outdoors. Viable seeds are going to sink to the bottom of the bucket, and the pulp will float to the top. Just let the pulp float out of the bucket until all you are left with are clean seeds in the bottom.
Next, drain the water from the bucket and evenly spread your depulped seeds in a single layer on a table for drying. After they have completely dried, store the seeds in a cool dry place. You can hold the seeds this way for an extended period of time.
Dogwood seeds have a very hard outer shell, which must be stratified before they will germinate. Stratification will soften the outer coat so that air and water can enter, which will initiate the process of germination. There are different ways to stratify the seeds, including treating them with acid or just storing them in the refrigerator. The following techniques will work best for someone with minimal stratification experience.
The first technique requires a bit of mathematics. Decide what day next spring that you would ideally like to plant your Dogwood seeds and then count backwards on a calendar for 210 days to begin stratifying your seeds. North of the Mason-Dixon line, May 15 is a ideal target date for planting as most will be safe from frost after that point. With all the work involved, you don't want nature to kill them off before they've even had a chance to grow. So, if we count backwards 210 days from May 15, we would be shooting for approximately October 15 to begin the stratifying our Dogwood seeds.
Stratifing the seeds using this technique simply requires placing them in a zipper lock plastic bag with some moist peat moss, or a mixture of moist peat and sand. The emphasis should be placed on moist, as you do not want the peat to be overly wet. Poke a few small holes in the bag as you don't want it to be completely air tight. Store the bag of seeds and peat at room temperature for 105 days, or until approximately the end of January. At this point, it's time to move the Dogwood seeds to your refrigerator for an additional 105 days, until the middle of May. It is important not to put them way in the back of the fridge where they could potentially freeze. You want to keep them cool, but definitely not frozen. At this point, your seeds are ready to plant outside and just in time to get past the last frost of the season.
During the storage period, it is important to check the seeds on a weekly basis. If you notice any sign of fungus growing inside, it's important to sprinkle a bit of fungicide in the bag. As you near the end of the storage period, begin checking for germination. When you see that about 10% of the seeds have germinated, it's time to plant them outdoors. If it is still too early in May to plant outdoors, plant them in a nursery tray indoors and make sure they get plenty of sunlight by placing them directly in a south facing window.
It's easy to plant your Dogwood seeds for propagation! Simply scatter the entire contents of the bag on top of your planting bed and spread it out. Then spread a thin layer of some light soil over top. It is important that the seeds are not planted too deep, a mere 1/4 inch is all you need. Be sure to water the area evenly and completely after planting, then allow the soil to go almost bone dry before watering again. Good drainage is imperitive, as soggy soil will cause your seeds to rot. This completes the first stratification technique.
Another method is to physically nick each seed using a sharp knife in a couple of different places immediately after the seeds are cleaned. They then can be planted immediately in the fall. A good tip for success is to cover the seed bed with a layer of screen to keep critters from digging them up and eating them. Rather than knife nicking, some growers throw them in a kitchen blender and let the blender do the work. Don't overdo it, though, it only takes a minute or so.
So which technique works better? Impossible to say. So many variables can affect the outcome. Most hobbyists will experiment with each way to see what works best for them. Many growers prefer to plant right away in the fall, but can be disappointed if something causes a poor success rate. Try some both ways and see what works best for you.
It's also possible to grow Chinese Dogwood (Cornus kousa) from seed. It is a very popular variety because it flowers much later than many other ornamentals. They are usually in bloom by late June with flowers that are cream colored against a dark green foliage which makes the flowers look almost mint green in color. Use the same techniques outlined above for Chinese Dogwood as well.
Copyright © 2013 by Jeff Edwards