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Tuesday, April 10, 2018

Why Does My Yellow Lady Banks Rose Have White Flowers?

Q. I planted three yellow Lady Banks roses on my south wall when I moved here 10 years ago. Two years ago, my neighbor planted a white, lady Banks rose nearby. This year I noticed white roses growing on my “yellow” Lady Banks rose. I thought these flowers might be from their plant but traced it back to the base of my vine. Will my yellow roses eventually all be transformed to white? How do you explain this botanically?
Some lady banks roses are grafted onto route stocks that produce white flowers. Is this a miracle when white flowers appear?

A. I wish we could declare it a miracle, submit it somewhere and have a party. But, unfortunately, it probably isn’t. What makes this observation even more interesting is that Lady Banks rose comes in two basic colors; yellow and white flowering selections.
White Lady Banks rose
            On rare occasions, a totally different plant can grow from a mother plant. This is called a “sport” in horticultural terms. These are genetic abnormalities, a mutant if you will. Most mutants are not valuable, wasted time in evolution, but sometimes they can be valuable.
Yellow Lady Banks rose
            One example is the nectarine. The fruit from a nectarine tree is basically a hairless peach. The tree is identical to a peach tree. If this hairless fruit had hair on it, we would call it a peach.
            The first nectarine, ever, was found by a farmer growing as a “sport” from a peach tree. Mutants like these can give rise to totally new types of plants which can become important commercially. If it wasn’t for this observant farmer, we wouldn’t have nectarines today.

            Back to your situation. 

Then how did these white flowers suddenly appear on a totally “yellow” plant? Unfortunately, the explanation is probably quite simple and not very “miraculous”.
Notice that this sucker with white flowers on it is coming low on the plant, close to the rootstock.

            Lady Banks rose is grown commercially by grafting the Lady Banks part, called the scion, onto a different rose plant used for its roots; the rootstock. This rootstock is a totally different kind of rose flower but it’s roots that have desirable characteristics that can contribute to the survival of the scion plant.
Lady Banks rose over the top of the wall
            In your particular case, the scion, the yellow Lady Banks rose, was probably grafted to Rosa fortuniana, a white rose commonly used for it’s very desirable traits as a rootstock.
            Rosa fortuniana shows excellent resistance to nematodes and a great deal of tolerance to poor soils. It is a very common rootstock used for roses planted in southern climates of the United States.
            These white flowers come from a "sucker" growing from this white “rootstock” rose. As it gets older, this sucker produces white flowers, quite a bit larger than flowers of the yellow Lady Banks, but an excellent rose in its own right just the same.
Yellow lady banks rose used as a screen on a trellis behind some retail establishments.
            You can elect to prune these "white suckers" from the mother plant and keep it totally yellow or let these suckers grow and have a beautiful combination of white and yellow flowers on the same plant. Some pruning may be required to achieve a balance in growth between the two roses so that one does not dominate over the other.

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