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RE: propagation failure (Follow-Up #25)

posted by: malcolm_manners on 07.08.2009 at 07:52 pm in Antique Roses Forum

Hi folks. Lots of good information above. So much of this may be redundant. But for what it's worth, here is an article I wrote many years ago (1994), with some updating notes at the end. Malcolm

Starting Roses From Cuttings

If you plan to do any propagation of roses, it is important to be able to root cuttings. If you want own-root plants, they are most easily produced from cuttings. If you intend to bud or graft plants, you�ll still need to produce the rootstock plants from cuttings. Fortunately, most of the roses which thrive in Florida are also reasonably easy to root. This article will offer some suggestions for maximizing your success rate.
1. Age of the cuttings: While most rose varieties may root at nearly any age, generally the best cuttings are taken from firm but young stems. On a repeat-flowering variety, that would be stems on which the flowers are fading or from which the petals have just fallen. On a once-flowering plant, you could also use stems from which the flowers are fading, in the spring, or similar-age wood from subsequent growth flushes throughout the summer or fall.
2. Leaves: Roses, like most plants, root best if the cutting has some leaves still attached. The leaves provide sugars from photosynthesis, as well as root-promoting hormones. Some varieties will root without leaves, but it is always better to have some leaves on the cutting. In Holland, cuttings are commonly made with only one leaf; most Floridians use more � usually 2 to 5. Be careful not to let the cuttings wilt, since they are far less likely to survive and produce roots after wilting has occurred. We keep a spray bottle of water handy to mist over our cuttings while working on them, to keep them crisp.
3. Cuts and wounds: Some plants are picky about exactly where the cut is made, its angle, etc. However, most roses are not at all finicky � you can leave a bud and leaf scar (node) at the base, or you can leave just a smooth area of stem (internode) � roses have the ability to form roots at any point along the stem. For very difficult varieties, there may be some value in making the cuttings with a node at the base, since node areas tend to root somewhat more readily.
Many people wound the base of the cutting, either by making vertical slits in it with a knife, 1/2 to 1 inch long, just scoring the bark, or by tearing the bark off of one or two sides of the base of the cutting with the pruning shear blade. I�ve also heard of people pounding the bottom 1/2 inch or so of the cutting with a hammer, to shred it. There is reason to believe that wounded cuttings root better than those without wounds, although I don�t recommend the hammer method.
4. Rooting hormones: Most rose varieties can be rooted without the use of hormone preparations. This is because rose cuttings contain auxin (indoleacetic acid; "IAA"), a natural root-promoting hormone. It is produced by the leaves and growing buds or shoot tips and accumulates at the bottom of a cutting, exactly where you want roots to form. Some roses apparently don�t produce adequate supplies of auxin, so are difficult to root, or if they root at all, they produce few, weak, roots. So, many growers apply a commercial hormone preparation, such as Rootone-F, Hormodin I or II, Hormonex, Dip-n-Gro, Rhizopon, etc. These products all contain a synthetic auxin, usually indolebutyric acid (IBA) and/or naphthaleneacetic acid (NAA). While natural auxin (IAA) is commercially available, it is almost never used for rooting cuttings, since it is astoundingly expensive and doesn�t work as well as the other two materials. Applied auxin materials generally do not speed up the rooting process, but they do result in a higher percentage of the cuttings forming roots at all, and a greater number of roots on each cutting,. At FSC, we�ve used a number of products, all with reasonably good success. Recently, we�ve used Hormodin II almost exclusively. It�s readily available, relatively inexpensive, and very effective.
5. Willow water: Another material which has somewhat of a cult-like following, is willow water. Cuttings made from willow trees (Salix spp.) are exceptionally easy to root, and it has been found that if pieces of willow twigs are steeped in water for a period of time (there are many recipes � perhaps we can publish some later), then cuttings of some other plant (e.g., a rose) are soaked in the brew, the cuttings become easier to root. Dramatic results have been shown with birch trees, rhododendron, camellia, and mung beans. The theory is that auxin alone is insufficient to cause rooting; there must be an additional substance, tentatively called "rhizocaline," which acts with auxin to stimulate root formation. Plants with an abundance of both substances are easy to root with no external hormone applications. Plants which root easily with a commercial auxin preparation must have adequate natural rhizocaline, but they lack adequate auxin. Still other plants, which are difficult to root even with an auxin preparation, must lack natural rhizocaline. It is these plants which would benefit most from a willow water treatment. It�s a nice theory, which seems quite reasonable, and there appears to be good evidence in its favor. But the substance rhizocaline has never been isolated and identified. Also, there are apparently no published data indicating that it is beneficial on roses. To date, I�ve never seen the results of a well-designed scientific experiment, testing the effects of willow water on roses. We tried to do such an experiment at FSC, a couple years ago, but all of the cuttings rotted (note, that�s rotted, not rooted). So, we didn�t prove anything. We�ll have to try it again. There are many rosarians who use it regularly, and are quite convinced that it is highly beneficial.
6. Moisture: One of the most important factors in successfully rooting cuttings is maintaining adequate moisture, both in the soil and in the form of humidity in the air. Commercial growers usually use an intermittent mist system, which sprays a fine mist of water over the cuttings for a few seconds, every few minutes, preventing wilting. Most such systems are set up with two clocks, one 24-hour clock which switches the system on at sunrise and off at sunset, since cuttings don�t need to be misted at night. A 10-minute clock (or some similar short period of time) turns on the water valve for the short bursts of mist at several-minute intervals, throughout the daylight hours.
If you don�t want to go to the effort and expense of installing a mist system in your garden, Charles Walker demonstrated an effective, inexpensive substitute, at the Heritage Rose Foundation conference here, in the spring of 1992. You stick your cuttings in pots (1, 2, or 3-gallon sizes are convenient), then cover the pot with a plastic bag. You can use sticks or stakes in the sides of the pot to hold the bag up off of the cuttings, and you can tie or rubber-band the bag to the sides of the pot (see illustration).
7. Light: If you have an open mist bed, which doesn�t build up heat, we find that the brighter the light is, the better rooting we get. FSC�s mist bed gets full sun from about 10:00 a.m. until nearly sunset. If you use the bag-over-the-pot method, you�ll have to provide some shade to prevent the cuttings from getting too hot.
8. Season: Most cuttings seem to root best for us in the spring, after the weather is warm but before it becomes miserably hot. May and June are good months. But we do root cuttings all year. They take longer, and a smaller percentage of them root in cold or very hot weather, but we can get reasonably good rooting nearly any time.


I�ve been told by Mike Shoup, of the Antique Rose Emporium, that Gallica roses are most successfully rooted in October, so if you are rooting something that doesn�t work well at one time of the year, it may be worth trying again at a different season.
9. Timing: In May or early June, some varieties will have good roots in as little as 2 weeks. Nearly any variety can be rooted in 3-4 weeks, that time of year. At other times, the process takes longer, up to 7 or 8 weeks in December - February. There are several ways to tell whether a cutting is rooted. You can tug lightly on it, and if it resists being pulled out of the pot, it is likely rooted. Also, you can look for roots growing out the drainage holes in the bottom of the pot. Cuttings which are putting out a flush of new leaves almost always have roots, whereas unrooted cuttings tend just to sit there, not showing signs of new top growth.
Once your cuttings are rooted and you�ve removed them from the mist or the bag, harden them off for a few days by putting the pots in a cool, shady area. Moving them immediately into hot sunshine may damage or even kill the plants. Once they have a good large root system and are putting out new growth, you can move them into brighter light.
If your goal is the production of rootstocks for budding or grafting, you should wait several (4-6) weeks after rooting the cuttings before you do the grafting or budding operation. Working on them any earlier is likely to break off a lot of tender roots as you jostle the top of the plant around. Give the roots time to toughen up first. Of course, you can "cleft bench graft" your plants, making the graft before rooting the cutting, then allowing the plant to root and heal the graft union at the same time.
Malcolm Manners

2009 update notes:

1. Hormones. We still use Hormodin II or Rhizopon II quite a lot (0.4% IBA in talc), and still like it. But for difficult-to-root roses, we sometimes use a #3 powder (0.8% IBA) with greater success. We've also come to like Dip-N-Grow liquid (1% IBA + 0.5% NAA in alcohol), which you dilute -- 1 part DnG to 9 parts water for very easy stuff (e.g., Chinas), 7 part water for "average" things, and as strong as 4 parts water for very difficult stuff. If using a liquid, let the base of the cutting soak in it for several seconds (we do 10 seconds) before sticking into the soil.

2. Willow Water. After writing the above article, we did quite an elaborate study, using 'Fortuniana' as the test subject, and on another occasion, R. moschata cuttings. What we found was that willow water alone never improved the percentage of cuttings which rooted, over the control. IBA-based hormones DID dramatically improve the percentage of cuttings which rooted. However, IBA-based hormone PLUS willow water resulted in cuttings with far more roots, longer roots, and better-branched roots, than did the IBA alone. So in that sense, we found benefit in using willow water, but not by itself.

3. One more note on a mist bed -- roses like the brightest light you can possibly give them, without cooking them, to root. So the problem with the bottle, baggie, or other method using an enclosed chamber, is temperature control while getting adequate light. The nice thing about a mist box is that you can leave the top open (no roof), so they get full noon-time sun, yet they stay cool. That's what our mist bed does, and we claim to be able to put roots on an old broom handle (well, almost)! I really believe in bright light, without too much heat.

Malcolm

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clipped on: 02.17.2013 at 07:49 pm    last updated on: 02.17.2013 at 07:49 pm