Dahlia

Dahlia Dahlia plants can be easily propagated in several ways: division of root system, cuttings, and from seed. Division of the root system and cuttings have the advantage of reliably reproducing the same flower that had been produced by the parent plant.  Propagation From Seed: Dahlias hybridize readily; flowers of hybrids can be radically different from the flowers produced by the parent plants. So propagation from seed can result in unexpected results when it comes time for  blooms.  Easy hybridization has a positive aspect: a wide variety of flower forms and colors can be produced by dahlia plants, and new varieties are constantly being developed. Dahlia hybridizers work tirelessly (not to mention their plants) to develop some really spectacular flowers - great new varieties are introduced every year.  The negative aspect of easy hybridization is that seeds will not relaibly produce flowers similar to the parent plant. In some cases exciting new flower varieties will result. But in most cases the flowers will not be as spectacular as the parent plant.  So if you want the excitement of growing brand new varieties - plant seed, you will get interesting if not spectacular results.  But if you want to know what kinds of blooms you'll be getting, it's best to propagate by division or cuttings.       Propagation by Division of Root System: During the growing season a number of "tubers" will develop in the soil surrounding a dahlia's stems; the tubers are a part of the plant's root system.  The tubers can be separated from the root system and re-planted to produce new plants the following season. The plants which emerge from the tubers will be "clones" of the parent plant - not hybrids.  So they will produce flowers that are identical to the flowers of the parent plant. For the most part the plants grown at the farm come from tubers or cuttings - because there's just not a lot of room to experiment with hybrids here.  (but if we had a spare acre or two there'd be some hybridizing going on) Seattle's first Autumn frost in 2011 was in early November.; the dahlias at the farm were all going strong and producing flowers until the night of the frost.  All the stems, flowers and leaves died back immediatley.  That was the end of the season for flower production. But the dahlia roots are not damaged by frost. A hard freeze can cause damage if the soil is frozen to the depth of the roots, But that's a rare case for November in Seattle .  So in the Seattle area it's generally OK to leave your plants in the ground through mid-November.  In fact, depending on soil conditions and the severity of the weather, the plants can be left in the ground all year without a problem.  But if you want to propagate your plants, November is a good time of year to remove and divide the root system.  We waited a week after the frost before digging up a number of plants at the farm. The tip of a shovel is slipped under and around the root ball and the "clump" is carefully lifted clear of the soil.   Here's a photo of a plant that has been removed from the soil - the tubers are the skinny potato-like things.  The roots of this plant have been carefully washed and the plant has been labeled with a big pink tag indicating the variety name - the label is important if you want to keep track of which varieties you are planting the following year. Be careful when removing the plant from the soil - the "necks" of the tubers are small and easy to bend - it is very important that the necks not be bent or damaged. In order for a tuber to produce a new plant, the tuber must maintain attachment to at least one "eye".  The eye is the part of the tuber which will become the stem of the new plant; without an eye the tuber will not produce a plant.  A number of eyes can be seen in the following photo - they're the greenish/reddish bumps near the center of the photo (zoom in for a closer look). Not all plants will have eyes which are this easy to see.  Careful examination is typically required to locate the eyes; a magnifying glass can help with this. Note that the eyes are located at the skinny end of the tuber "necks"; the necks connect the bulbous portion of the tuber to the eyes.  This is why it is important to avoid damage to the necks - if the neck is damaged the stored energy of the bulbous portion of the tuber will not be available to the eye when it is time to grow. In this example there are several tubers which are connected into the area containing the eyes. But two of the tubers are very skinny with very thin necks. these will not be viable after a few months in storage; not all tubers are worthy of division.  But the larger tuber toward the bottom of the photo appears viable and has a good connection to several eyes.  This is a good candidate for division and propagation. And there's another good candidate toward the top of the photo.  Tubers are separated from the plant by cutting them away from the root mass and stem.  This is typically done using pruning shears, knives and other cutting tools. Larger root masses can be broken into more manageable sized clumps by using a shovel. This will result in splitting (ruining) viable tubers but in many cases it has to be done to allow room to maneuver the knives and shears. As cutting proceeds pockets of soil and pebbles will be exposed in the root mass; the root mass is continually rinsed with water during the cutting  process to remove the soil and pebbles. Here's a photo of the same root mass from a slightly different angle. The photo below shows some tubers which have been cut away from their parent plants.   Here's a close-up of the stem end of a tuber - showing what appears to be several eyes (the shiny white bumps). Once the tubrs have been separated they are marked to identify the variety type; The marking can be done with a "Sharpie" marking pen. But this requires that the tubers be dry before marking. It's really nice if you can mark immediately after dividing, when the tubers are typically wet from the cleaning process. until recently the Sanford company manufactured the "No-Blot Ink Pencil".  This was a great product - made specifically to mark wet things - it was ideal for marking wet tubers.  Now that the no-blot pencil is not available, growers are searching high and low for a replacement - let me know if you know of something that will work to mark a wet tuber.  In the mean time we dry the tubers before marking (or borrow a "No-Blot" pencil from a true friend). After adding the markings, the tubers are rinsed again in a mild bleach solution - (1/4 cup bleach in 3 gallons of water). The tubers are placed in a bucket with the solution and left for 20 minutes; after that they are rinsed in fresh water. The bleach rinse helps to avoid rot while the tubers are in storage in the winter.