5 Signs Your Rose is Reverting to the Rootstock
Roses are resilient, productive flowering shrubs, ready to perform for years in the right growing environment. Beyond our control is the propensity of grafted roses to revert to their underlying rootstock. Gardening expert Katheine Rowe points to signs your rose is reverting, what to expect, and how to manage the internal horticultural conflict.
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It’s a war of the roses when a specimen reverts to the rootstock, portraying two distinct plants in one. That’s a little dramatic, but when a rose reverts, one species or variety competes with another. Rootstock reversion occurs in grafted roses. Grafting is a popular and long-time propagation technique that fuses the hearty root system of one rose with the desired upper growth of another.
The innovative method yields quick-growing specimens that are economical to produce and tailored to certain growing conditions. They may grow in poor soils like sand or clay, tolerate cold, northern winters, or withstand southern summers, depending on the species.
While the rose doesn’t technically “revert,” meaning it doesn’t change back into a previous state, the underlying growth begins to show itself. When a rose reverts to the rootstock, it means the roots are sending up growth from one variety, while the upper growth of the desired variety eventually succumbs.
The showy upper possesses the blooms and attributes of the marketed variety, while its fused rootstock contributes to performance, like vigorous growth and sturdy roots that grow across conditions.
While pretty and productive upper growth from vigorous roots sounds like a winning combination (and it is, for a while), the grafted roses and their gardeners contend with reversion. The physical attributes of the rose selection can change before our eyes over time. Here’s how to spot a rose that has reverted to its rootstock, and what to do about it.
What is Rootstock?
Many modern rose hybrids are grafted, where breeders fuse the upper growth of one variety with the rootstock of another for hardiness, robust growth, and other selected traits. Rootstock is the stem and root system to which the upper growth (bud eye) attaches. Using sturdy stock is an easy way to propagate roses and capture traits of vigorous roots.
An original plant grows normally to become the rootstock (also called the understock). Then, a cutting from another selection goes into a cut on the lower bark of the original. The grafted cutting is wrapped until roots set, when the original growth is removed. You now have an upper rose, a graft union at the crown, and roots.
Grafted Roses
Grafting has a long history, originating with the first hybrid tea rose ‘La France.’ Melding ‘La France’ with a more vigorous rootstock allowed better garden performance. There are a number of varieties that serve as reliable rootstocks and depend on the grower, climate, and breeding for specific site conditions.
‘Dr. Huey’ is a standard for its reliable performance across climate zones, works in clay soils, and has good storage as bare root specimens. Fortuniana is a fit for southern climates, while Multiflora thrives in northern zones.
Other than propagated grafted roses are “own root” roses. Own root selections grow from cuttings with their own original roots. They may arrive smaller than grafted selections, but they don’t experience the reversion that comes with grafted types.
Your rose likely won’t come with a label indicating whether it’s grafted or own root. Look for a graft union at the crown. The bud or graft union looks like a knot or swollen point at the base of the plant, just above the roots. A healthy bud union should feel firm and is where the canes for the upper variety develop.
When sourcing grafted roses, you’ll find three grades based on the number and caliper (diameter) of the canes: #1, #1 ½, and #2. Grade #1 is the largest and best for the strongest selection at the start. Smaller grades cost less and catch up in growth over a longer period of time, but #1 is the best bet.
Look for a #1 grade with:
- At least three strong canes
- 5/16 of an inch caliper or greater
- Branching that begins less than three inches from the grafting point at the crown
Vigorous, Suckering Shoots
If you spot uncharacteristically vigorous canes and leafy growth at the base of the shrub, this is most likely understock growth. The roots of the existing specimen are sending up their sprawling shoots. They compete with the grafted rose and eventually crowd it out, left unchecked.
Prune out suckering offshoots as soon as you notice them. They emerge from beneath the bud union and can go undetected as they grow. If left to develop, you’ll have a blended rose with long canes vying for the same resources, like moisture, sunlight, and nutrients, as the desired variety..
Rootstock varieties aren’t usually sought after as ornamentals. They’re often rambling types with a once-a-season bloom. They may show increased disease susceptibility to rose rosette and mosaic virus.
Different Blooms, Same Plant
While it might seem like one of nature’s miracles or at least oddities to have different blooms on the same flowering shrub, the science leads to the rose reverting to its rootstock. The canes sent up by the original rooted variety begin to bud and bloom along with the rose you purchased. Over time, you may only see blooms from the robust rootstock, and not the selected variety, if the rootstock species takes over.
The rootstock has the ability to overtake the existing upper growth, especially if the bud union experiences damage through extreme temperatures or disease.
Varying Leaves
Like the flowers, the foliage will show differences between the understock and the upper selection. Rose foliage may be glossy and deep green or tinged with red and purple as it emerges. There may be lots of little leaflets or more broadly pinnate leaves. As it varies by species and variety, the two present differently.
Look for the varying leaf shapes, colors, or sizes, and trace them back to their source canes. Identify the variety you planted and cut off the other at its base.
Winter Damage
The graft union, where the upper growth meets the crown, is sensitive to frigid conditions. If the union is cold-damaged, the upper growth suffers. It may die back completely, leaving only the rootstock to survive. The rootstock then produces suckering offshoots, and the rose reverts.
Own root selections are less vulnerable to cold damage. Those with upper growth that dies back in the winter may recover if the roots are healthy and intact.
Provide extra winter protection around roses. In warmer zones (7 and higher), extra mulch is usually sufficient for successful overwintering. Topdress with two to three inches of mulch (bark, compost, clean straw, chopped leaves, evergreen boughs) for insulation. Colder climate roses in northern zones and high elevations benefit from further winterizing, depending on the selection.
Enlarged Bud Union
A large, swollen joint at the base of the shrub means the grafted rose may be outgrowing the bud union. With a shorter life expectancy than own root roses, grafted roses show decline as the two compete over time.
Depending on the variety, own root roses are long-lived, lasting for 50 or more years. Grafted roses are likely to live for 15 years or less. Own root roses tend to be more resilient, disease-resistant, and cold-hardy, though they take longer to establish than the quick-developing grafted varieties.
