Two New Ways of Growing

Very soon we're going to be growing roses differently from the way we do now.  There are two new ways you should know about.  One approach has been around for a while, and it is simply being perfected.  The other is in its infancy.

Roses on Their Own Root

Rose varieties that grow on roots they develop themselves have long been touted to be superior to those grown conventionally on rootstock.  When I first heard about them, I thought it was possible only with miniatures (minis grow on their own roots unless budded as standards).  Then I learned that people took fresh wood from a bush they wanted to try growing on its own roots and planted it in containers or directly in the ground.  Only recently have I learned that some varieties seem to grow better this way than they do when conventionally budded to rootstock.

You should know about a legal problem.  Roses that are hybridized and introduced for commerce have a seventeen-year patent, during which time they cannot be asexually reproduced.  Growing them on their own roots must be for personal use only.

Not having rootstock is a problem when cuttings first start out, since they can't develop massive root systems in a hurry.  I bought some bushes growing on their own roots a few years ago.  Their first year in the ground was thoroughly uneventful.  During the second year, I began seeing possibilities.  After three years, they're performing like their budded siblings.  Time is the factor.

Getting cuttings to root properly requires some technique.  Theoretically, rooting is possible any time of the year, but I wouldn't do it in the heat of summer without providing some shade.  Since I like to root cuttings in the ground where they are to grow, I do it at pruning time when excess heat is no longer a worry.  Commercial rooting stimulants are a big help.  You simply immerse one end of a freshly cut stem into it before sticking the stem into the ground.

Five budding eyes per stem seem to be the magic number for successful rooting.  Three years go underground.  Either or both eyes left above soil level will sprout if the rooting takes.  The soil in which cuttings are expected to root should be highly friable.

During the last pruning season I decided to try some varieties I've heard do well on their own roots.  A college student who works for us part-time saw me doing it and suggested something I was embarrassed not to have thought of myself, since I had seen my grandmother do it many times.  The idea was to place fruit jars over the cuttings.  These glass shelters are a great boost for successful rootings.  First, they protect tender new growth from crippling cold snaps.  Second, they create a microclimate in which warm moisture seems to coax sprouting.

I've seen plants of Altissimo (which was introduced in 1966 and has lost its patent protection) that are bigger and healthier than any I've seen budded on rootstock.  Try taking cuttings of any variety you like, but if the variety is younger than seventeen, don't try to peddle them.

Tissue Cultures in Vitro

Tissue culture is a process in which selected portions of a plant are grown on an artificial medium under sterile conditions.  Cultures are grown in glass vessels, hence the name in vitro.  Quick propagation of orchid species spurred early tissue-culture efforts.  Other flowering plants have since been tried, and it was inevitable that successful cloning would extend to roses.

The first step for tissue culturing roses is the selection of bud eyes from virus-free bushes.  Next is disinfestation, which rids cuttings of fungi and bacterial contamination.  Once sterilized, buds are set upon an artificial medium within a sterile test tube.

The type of growth that develops from cultures is a function of the medium in which the buds are propagated.  One formulation of nutrients, vitamins, and growth regulators encourages shoot development; another promotes roots.

Shoots are encouraged first.  Several plantlets sprout from each bud eye within three weeks when light cycles, temperature, and humidity are all carefully controlled.  Once sufficient shoots have developed, they are transferred to a new artificial medium formulated to encourage strong, healthy roots.  When well rooted, the tiny rose plants are removed from their test tubes and planted in a greenhouse to acclimatize them to growing in a soil medium.  After two to three months of greenhouse care, plants are ready for commerce in disposable plastic containers.

In America, tissue culturing of roses is being pioneered by Armstrong Nurseries.  Its parent company, Moet-Hennesy, has constructed a laboratory in Somis, California, modeled after a similar facility operated by Delbard Nurseries of France.

I visited Armstrong Nurseries to see the experimental laboratories there and left with some established tissue cultures to evaluate in our growing field.  I'm impressed with what they've done.

I planted the tissue cultures next to my rosebushes of the same varieties that are growing on conventional, budded rootstock.  The first bush bloomed one day short of three weeks after planting!  Such quick reward will surely be a good marketing feature, as will the fact that bushes are growing on their own roots, thereby never producing sucker growth.  Finally, bushes that can be planted anytime during the growing season are certain to be more salable than those restricted to the comparatively short bareroot season.

Will tissue-cultured rosebushes replace the budded-onto-rootstock varieties?  It's too soon to tell.  Among other things, the impact on hybridizers' patenting protection must be resolved.  We must also look at costs down the road.  On the one hand, budding roses onto rootstock is painstakingly slow and labor intensive, making costs ever on the rise.  Tissue culture, on the other hand, offers a method for more rapid plant reproduction at which is likely to be a fraction of current costs.  The day may well come when we never buy another rosebush with a bud union on it.