Back to Your Roots
Rootstock Options For Growing Your Roses
By Kathy DeRoo
Twenty years ago, I wrote an article about rootstock entitled, “Discover Your Roots.” The basic information about the individual rootstocks is still true, but there have been some new discoveries and innovations over the years, as well as many changes in the rose industry itself, that have had an impact on how roses are grown and propagated.
Most of our modern roses are budded or grafted onto the rootstock of another rose. Basically, a bud-eye is taken from the desired rose plant, such as Peace, and grafted to the stem of a growing rootstock plant, below the bottom set of leaves. After the bud-eye produces adequate growth, the top of the rootstock plant is cut away entirely, leaving Peace growing on the roots of the understock.
There are several advantages to this method of propagation, for both professional and amateur growers. To begin with, it is the most efficient and cost-effective way to produce a large number of roses of a single variety. Budding requires only one bud-eye per plant, whereas each cutting would require 3 or 4 bud-eyes. Also, budding tends to improve vigor (more so with the older varieties of the 1940s and ’50s), and produces more uniformity in the quality of the plants. In backyard propagation, budding is considered to be an easier means of reproduction than by rooting cuttings, according to Justin Ekuan of Dana Point, California, a rosarian who has spent many years experimenting with a variety of rootstocks. Also, he says, “There’s no question that grafted roses are far superior in size and bloom production – at least twice that of own-root roses.”
The most commonly used rootstock is the Climber Dr. Huey. Tom Carruth, Director of Research & Marketing at Weeks Roses says, “We use Dr. Huey predominately. It propagates easily, it has a long budding season, the plants harden off and ship well, they store well when bare-rooted, and the general adaptability to the broad area of climates and soils that we ship to is pretty good.” Also, it does well in the growing fields in California, which produce about 80% of this country’s roses (other than Minis and MiniFloras). Unfortunately for the rosarian maintaining rootstock in the garden, Dr. Huey tends to mildew (a trait that is not passed on to the budded rose).
For standards, or tree roses, most nurseries use a full-length cutting of Dr. Huey: For a 36” tree, a 38” cutting is stuck in the ground, staked, and covered by a long, plastic sleeve (for protection while rooting), then de-thorned and de-eyed by hand, and grafted two to four times (around the top of the cane) with the desired cultivar.
Jackson & Perkins recently patented a proprietary rootstock known as RW, bred specifically for tree roses. It is a cross of a cold-hardy Griffith Buck rose and Odorata, another understock variety which produces a vigorous root system. Dr. Keith Zary, formerly Head of Research at J&P, says, “[RW] is hardier than Dr. Huey, greener, more mildew resistant, grows straighter with smoother canes, and roots well. In the field it grows 15 feet a year.”
Phil Edmunds, formerly owner of Edmunds Roses in Oregon, said he used Burr’s Multiflora for locally grown roses because it is a good, all-around fast performer for their shorter growing season; it’s winter-hardier than Dr. Huey, it grows faster, and roots quickly in Oregon’s colder climate. Multiflora is not used much in California as it is inclined to pick up salts and is not “happy” in alkaline soil. Edmunds Roses, now located in Wisconsin, currently grow all their roses in California on Dr. Huey.
Hortico in Canada uses Rosa multiflora seedlings for most of their stock, one seedling per grafted rose, in order to minimize the incidence of mosaic virus (a disease that is transmitted from the rootstock to the rosebush or vice versa). Chances are only 1 in 10,000 of getting an infected seedling.
Ekuan states that Multiflora is very sensitive to virus; when an infected bud-eye is grafted onto it, even the mildest case of virus will show substantial infection. He uses it to test questionable budwood.
Fortuniana is an understock that was originally used in Florida gardens in this country in the late 1950s. According to Dr. Zary, who is currently Director of Ornamental Research at Gardens Alive!, “Fortuniana is a very vigorous rootstock, but extremely cold sensitive and doesn’t respond very well to freezing weather; it dies quickly.” It also prefers acidic soil and doesn’t do as well as Dr. Huey in the alkaline conditions of California’s growing fields. However, researchers at the University of Florida have concluded that Fortuniana is resistant to gall, nematodes, and stem dieback, as well as many root diseases, performing better than all other rootstocks tested there. Fortuniana is also purported to live and produce years longer than any other rootstock.
Kitty Belendez, southern California Master Rosarian, orders virus-free Fortuniana cuttings from the University of California at Davis to root them and chip bud her favorite varieties of all types of roses, including Minis and MiniFloras. She says that plants grown on Fortuniana do very well in her sandy soil: “They grow really fast, the bushes get really big, and they produce lots of blooms.”
Dr. Malcolm M. Manners, Chair of the Horticultural Science Department at Florida Southern College says, “I prefer most roses on Fortuniana, even if they do well for us own-root, simply because they grow better and bloom more on it. There are a few exceptions - some of the Austin roses grow way too large and bloom too seldom on Fortuniana roots; I prefer them on Dr. Huey. Also for the rose show crowd, Minis grafted to Fortuniana often make blooms so large that the judges score them down because of the size, so they don't win. But for most roses, it's a great stock.”
Jackson & Perkins and Weeks Roses both use Fortuniana on a small percentage of their roses specifically targeted for sales in the gulf coast states. But Carruth says that for the large rose supplier, “It is highly unprofitable – Fortuniana is more difficult to root, graft, dig, and ship, and it suckers like mad.” While Belendez agrees that it suckers slightly more than Dr. Huey, she says it is easy to identify Fortuniana growth quickly by its distinct foliage, and it is easily removed.
Odorata was a favorite of hybridizer Joe Winchel until his source-plants succumbed to Downy Mildew. Odorata works well for “bench grafts,” where the graft is done at the same time as rooting the cutting of the rootstock. Justin Ekuan claims it is a vigorous rootstock but says that it is susceptible to crown gall and “it suckers like crazy – the champion!” He has discontinued using it in his propagation program.
Ralph Moore hybridized the miniature climber Pink Clouds in 1956 and used it for rootstock and for the stem of his Miniature tree roses. Justin Ekuan uses Pink Clouds today with all types of roses. He says it never goes dormant for him, it roots easily right through winter, and he particularly likes it for Miniatures. Most Minis and MiniFloras are grown on their own roots, but some lethargic varieties grow much more vigorously when budded onto Pink Clouds.
Whatever rootstock is used, once the plant has been budded and is growing on the understock, it takes its inherent qualities from the grafted cultivar. No rootstock can improve disease resistance or bloom form; if a cultivar is inferior, it will not do well on any rootstock.
Although some cultivars do better than others on certain rootstock varieties (e.g., Odorata is said to work better with yellows and yellow-blends than red-family roses), generally, rootstock is chosen for its performance (before it is grafted) in the region where it is grown and propagated.
One more option is the own-root rose. Dr. Zary says that the advantages of not grafting a rose to rootstock are that it is cheaper, there is no suckering, and plants are considered to be more cold-hardy – if the plant freezes down to the crown, it can still come back up as the desired variety, not a rootstock rose. Modern roses that grow well on their own roots are Climbers, Shrubs, Miniatures, MiniFloras, and many Floribundas.
Despite attempts to breed better rootstock, the majority of rose suppliers continue to favor Dr. Huey for its commercial advantages. The enduring predominance of Dr. Huey rootstock in the rose industry proves the old adage, “The more things change, the more they stay the same.”
LINKS TO MORE INFO ON ROSE PROPAGATION:
© Copyright Kathy DeRoo. All rights reserved.
Originally published in "Rose Ecstasy," bulletin of Santa Clarita Valley Rose Society,
Kitty Belendez, Editor.
Photos © Copyright by Kitty Belendez
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