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On any given morning, Farmer Tony might be seen driving a tractor along the stool beds of G.11 in the field. “What is a rootstock? What is a stool bed? What is a plant? Why do these things matter? Who is Dr. Jim?” These are all questions that Tony asks himself as he drives the tractor along the stool beds in the field of G.11’s.

What is a rootstock?

Most fruit trees are grafted and consist of two parts, the upper part, which is the variety, and the lower part, which is the root system. The root system portion of the tree is called a rootstock. Preserving a desirable variety by grafting the variety onto a rootstock is a propagation technique that has existed for thousands of years. Before the creation of the Malling series, rootstocks were grown from seed, but seedlings are, like children, unpredictable. Rootstocks control the size of a tree, and seedling rootstocks produced tall trees, short trees, and average-sized trees. There was no way to predict a tree’s eventual size. The rootstock might survive in heavy soil, or it might die. The rootstock breeders who started programs in East Malling and Merton England in the early 1900’s wanted predictable trees, and these breeders began to develop rootstocks that would consistently produce trees of particular sizes. M.7, M.9, MM.111, M.26 and MM.106 were developed in this program, and hundreds of thousands of these rootstocks are still produced yearly.

How are clonal rootstocks produced?

The original M.9 apple tree grew from a seed and was small. It sent up a sucker from its roots. A gardener came along and mounded up a little dirt around the base of this sucker and then came back in the fall to discover that roots had developed in the mounded dirt. The gardener clipped the sucker at ground level and, voila, a clonal rootstock is created! Not merely a horticuluralist, but also a poet, our gardener names the rootstock M.9, and it is identical in every way to its mother. Now, a scion from the huge, old Ashmeads Kernel growing in the backyard is grafted onto the baby M.9, and a tree is created. The rootstock is an M.9 clone and the scion is an Ashmead’s Kernel clone. The tree grows up to be a… small tree, because the rootstock controls the size of the mature tree. But hey, small is nice! Not only is it small but it starts producing Ashmead’s Kernel apples in just 2 years instead of 6, 7, 8, or 9 years! “I wish I had more M.9 rootstocks,” says the gardener. Fortunately, the original M.9 tree has continued to produce many suckers, so the gardener mounds the dirt again, and so on.

What is a liner? What is a stool bed?

This original M.9 is a true giving tree. Unfortunately, it doesn’t give enough because all of the neighbors want baby M.9’s, which folks have started calling liners. The clever horticulturalist takes the rootstock liners, plants them in a row, and grows them out for a couple of years. It turns out that cutting the rootstocks off at ground level will force them to send up many shoots, and for each rooted M.9 liner that is planted and beheaded, two more grow. The dirt is mounded around the young row, which is harvested again in the late fall. The following year, there are four shoots popping up from below ground. This process is repeated every year, and by year five, this one-acre stool bed is producing 35,000 M.9 rootstocks! All are exactly the same as the original M.9 mother seedling, and our gardener has become a stool bed operator.

Why does this matter?

Initially, rootstocks were chosen mainly for their ability to control the size of a cultivar. They were also chosen for their propensity to root. This was a great beginning. However, there is always room for improvement. The perfect rootstock would be immune to every known apple disease, nematode and insect. It would have excellent anchorage, so that the tree it supported would never fall over, and it would form a strong union with its scion, so that the graft union would never snap. Rodents would spit it out. It would have no burrknots. It would be precocious, producing large fruit in its second or third year in the orchard. It would be able to withstand extreme temperatures, and it would leap tall buildings in a single bound. This would be the super rootstock. Alas, we are not there yet, but some important improvements have been made since the first M.9 stool bed was created.

Who is Dr. Jim Cummins?

Dr. Jim Cummins is my father, and he began breeding apple rootstocks in 1968 at the Cornell research station in Geneva, NY. His goal was ambitious: he wanted to create the perfect series of size-controlling apple rootstocks, and to a large extent, he was successful. The Geneva series of rootstocks vary in size from super-dwarf G.65 up to full-sized Novole. Dad’s first introduction, Novole, was resistant to phytophthora and fireblight, and voles would not eat it. Unfortunately, Novole did not readily produce roots in the stool bed. Dad’s second introduction was G.65, which Mom named Little Beauty. It turned out to be too dwarfing and, again, it was very reluctant to root. Next came G.11, G.16 and G.30. These have been around since 1992 and millions of them are now planted all over the world. G.202, G.41, G.210, G.890, G.969, G.214, G.935 followed, and the list continues to grow. These are all roostocks that have been released by Cornell from Dad’s original crosses in the 70’s and 80’s. All are resistant to fireblight and phtyophthora, and they are all productive and precocious. All are cold hardy and tolerant of heavy soils. They all have adequate to excellent anchorage. Some are resistant to replant disease, some to wooly apple aphids. None are truly perfect, but they come close. Good job Dad!