Rooting Junipers

Wednesday, March 21, 2012
I know I’ve done it, and you probably have, too – tried and failed to root a cutting because a plant is clearly dying. A few weeks sooner and my efforts might have worked, but there comes a point when a plant is just too neglected, too infested with insects or infected with disease to root. The success percentages also go down generally when the tip has a flower bud on it or is very young or old. One group in particular, the low-growing junipers, roots best from young stock. That means you can readily multiply these popular landscape plants right after you purchase them and have more in the garden in 6-12 months. On the other hand, it also means that routine prunings and cuttings taken from junipers more than a few years old can be reluctant. Unfortunately, I learned this lesson through trial and error, but you don’t have to – here’s what works. Creeping and crawling, low-growing junipers like Shore (Juniperus conferta) and Green Mound (J. procumbens nana) are not very difficult to root. Many sources say that the best cuttings for these plants are taken in late winter, but I have had better success in late March, or what is technically early spring. Juniper roots best from cuttings taken from wood that is one year old at the branch tips and has been exposed to at least some cold weather. Take tip cuttings from a major stem rather than a side branch if possible and make them 4-8 inches long. While many people always prefer a smaller cutting to a larger one, it is good to remember than a larger cutting (within reason) becomes a larger plant sooner. Junipers can hold enough moisture in their needles to prevent dehydration even if you take a longer cutting. I have rooted 4 inch shoots, but a couple more inches makes them easier to handle. Strip the needles off of the lower 2 inches of the cutting and further wound it to promote rooting by also removing a thin sliver of bark from each side of the cutting. Dip the exposed base of the cutting into full strength Hormex Liquid Concentrate or roll it in Hormex Rooting Powder #3 before inserting it into the rooting box or pot. The soil media has to be able to hold some water, drain the rest and thus provide oxygen to the cuttings. It also must be sturdy enough to hold the cutting in place for weeks or months. For woody plants like juniper, a good combination is equal parts of sand, peat, and perlite. A lightweight peat-based potting mix can work, too. I like to dampen the mix before putting it into small containers and watering it thoroughly once. Let it rest until it is just damp (15 minutes to half an hour) before sticking the cuttings. More than green stems, woody cuttings may require additional humidity around them during the rooting process. Their ability to take up water is seriously compromised and the top can wilt fatally in dry air. Intermittent mist systems are ideal, but a good alternative is a clear glass or plastic box over the cuttings. While juniper will not root in the dark, direct sunlight is not necessary. Heat will build up quickly inside the box even in the safety of lower light. Keep a spray bottle of water handy, open the box daily for ventilation, and mist whenever the air inside the box feels uncomfortably warm. Indeed, junipers seem to root best for me when the temperature is about 60 degrees, and they go quickly if I let the box temperatures get over 70. It’s a balancing act, certainly, but not hard to care for once you get it going. Some will want to use a heating mat under the cuttings to raise that temperature a few more degrees, but unless the spring is very cool, I don’t find it necessary. These tips work well for the small mounding and trailing junipers, but larger species do not respond to them in my experience. I love big Hollywood junipers as much as the little ones but have yet to be successful rooting one of those. Maybe the plant was too old, or young, the cutting to big or small, but something was off. Maybe next time…
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