Propagating Live Oaks

Wednesday, June 27, 2012
Rhizomes, Stolons, and Clones A question came to me recently about cloning live oak trees, which is best done from root cuttings or sprouts that arise from underground rhizomes. The ensuing discussion made me think more about the amazing power of rhizomes to sustain even a forest. Here are some facts about them and their compatriots, stolons, and how we can put them to work in the rooting bench. In the world of horticulture, a rhizome is modified stem tissue that forms a storage organ usually underground and has the capacity to grow roots and shoots. Probably the most familiar garden examples are cannas and irises, but many trees also produce rhizomes that will sprout new stems at almost every node. This habit can be a two edged sword, depending on the tree and the environment. For example, the beloved aspens of the American West can be ravaged by fire or insects yet survive with rhizomes undamaged. Soon they sprout to repopulate and expand the stand. But when an old crepe myrtle must be cut down to make room for a home addition, its rhizomes grow on. Those creeping rootstocks can send up sprouts across the lawn for years to exasperate the homeowner. A nice patch of Alstroemeria spreading under a tree may be nice, but if it is Johnson grass sending out those rhizomes, our reaction is decidedly negative. To root a sprout taken from a rhizome, first prepare the rooting medium to suit the plant. Edible ginger is a rhizome and can be broken into pieces that will root to become tasty clones of the original. Such fat plant parts, often with much exposed tissue, root best in 2 inch pots filled with damp sand. The swollen rhizomes of bearded iris plants should be pressed gently into the rooting medium, whatever it is, with the top third of the rhizome exposed to sunlight. These and other herbaceous plants will benefit from weekly watering with Hormex Liquid (2T/qt of water) during the rooting process. While many perennials will root in almost any mix, tree rhizomes need the finer texture of a soilless mix that is dense with peat and perlite or sand. A cutting 6-10 inches long needs a tall, narrow pot such as quart sized perennials are often sold; a 1 gallon pot can hold about 6 such sprouts. Water the mix well and let it drain until just damp, then dip the cut end in full strength Hormex Liquid for 3-5 minutes or roll the end in Hormex Rooting Powder. The best example of frequently cloned stolons must be spider plant, aka airplane plant aka Chlorophytum. Stolons arise from living stems, send out long stems with inches between growing nodes, and can sprout viable plants. This charming habit allows the basket of mother plants to erupt with satellites. Strawberry plants fling stolons over the edge of their baskets, too, and the whole effect looks like the mobile over a baby’s crib. Alternatively, those berry plants will send out stolons after they fruit and can fill a bed in one season with their offspring to form a natural groundcover for years of deliciousness. From the stolon’s point of view, of course, it’s all about insuring future generations and we get plenty to propagate. The easiest way to clone stolons is to set a pot or flat under the mother plant so the ends of the stolons just touch the lightweight rooting mix. Dip the tips in the appropriate strength Hormex Rooting Powder or dip baby plants into Hormex Liquid before laying them on the mix. Be sure stolons make good contact with the rooting medium for fastest root formation and yes, you can invent something to hold the plants in place at first. It’s a great use for old fashioned hair pins! One great joy of gardening has to be the endless fun of discovery when plants mature and begin to multiply. As reluctant as I am to admit it, the 8 year old in me gets tickled at the first sight of a canna baby. Clearly popping from a rhizome near the main plant, those little leaves amuse me every time and start me propagating again and again. That’s a clone joke – get it?!
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