Glenn Davis, UCCE Master
Gardener, El Dorado County
January 2003
Quite often when you purchase a bareroot tree there is a graft
joining the bottom of the tree to the above ground trunk. This area, sometimes called a “dogleg,” is the
graft of the rootstock to a scion or branch of a fruiting tree. Since a lot of trees do not do well in some
soils growers graft the tree onto a rootstock that will prosper in certain
soils. The rootstock will furnish the
tree with a support and feeding system that will help it to survive in an area
where it would otherwise have the possibility of trouble.
Generally the rootstock is from the same species as the tree,
that is apples use apple rootstock and stone fruit, such as peaches or
nectarines, use their own rootstock.
Rootstocks can dictate to some degree the size of the tree, the flavor
of the fruit, the ripening time, the amount of water needed, resistance to some
insects and diseases and the tolerance of certain soil types.
Often commercial nurseries order the fruit they feel will be
the best seller, unfortunately the fruit may come on a tree whose rootstock is
not well suited for the soil where it will eventually reside. Once you know the type of fruit tree you
want, ask your nurseryman, “what rootstocks are available for that tree and how
do they differ?” If they don’t give you
a good solid answer do a little research on your own.
Fruit trees generally come in “standard” (full sized tree),
“semi-dwarf” (medium sized tree), or “dwarf (miniature). All bear the same size fruit just in
differing amounts. Because of their
large size standard trees are more difficult to take care of, more water, more
pruning, more area to spray and more feeding are necessary. Semi-dwarf trees are significantly smaller
and easier to manage for home gardeners.
Dwarf trees are suited for small yards and patios since they rarely are
five feet high. Since size dictates
number of trees per square foot of garden space, you should choose rootstocks
that meet your space needs.
Some rootstocks are drought tolerant and some can survive in
extremely dense soil and very wet conditions.
If you don’t really know what kind of soil you have, here is a simple
test. Take a handful of dry earth,
dampen it until it is wet but not runny, rub it between your forefinger and
thumb. If it is slick it is clay,
gritty it is sand and a little greasy, with some particles, it is loam.
Remember, rootstocks are selected for their ability to prosper
in certain soils; some will do well in sand and some will do well in clay, most
will do well in loam.
Some rootstocks can fight off ground dwelling nematodes and
surface problems such as crown rot. If
you have experienced a disease or insect problem in the past, check with your
Master Gardener office to identify the problem and see if there is a rootstock
that is resistant.
No rootstock is going to be perfect. You have to balance the best you can by choosing one that most
meets your needs. Here are some
suggestions you might consider.
Apples: MMlll
rootstock resists woolly aphids, drought and cold and does well in clay. MM106 rootstock resists woolly aphids, is
slightly smaller and does well in sandy loal
Pears: OHXF513
rootstock resists fireblight, decline and does well in loam soil. OHXF533 rootstock resists fireblight,
decline, does well in loam and is slightly larger.
Stone Fruit: Citation rootstock resists canker, nematodes, does well in sand
loam. Mariana rootstock resists some
nematodes, tolerates wet soil, produces a larger tree, has very shallow roots
for the first three years.
These are only a few of the available rootstocks; when
purchasing your trees keep in mind the size and the soil type, these factors
will probably help you to decide which rootstock to use.
For more information on this subject or any garden problem,
contact the El Dorado County Master Gardener, 621-5512, Monday through Friday
9:00 AM to Noon.