OF THE WEEK
Dr. T. Ombrello - UCC Biology Department
|A grafted cactus growing in one of Union County College's greenhouses.|
a rule, cacti graft quite readily. Almost any two
cacti can be successfully grafted, and can produce
some interesting forms. Cactus grafting is often
tried by beginning grafters, while learning the
basic techniques. It is a great confidence
builder, because with a little practice one can
become quite good at it. But first, what is
art and science of connecting two pieces of living
plant tissue together to grow as one composite
– The lower portion of the graft, becoming
the base of the stem and the root system of
the composite plant.
Scion – The upper part
of the graft. A short shoot with one or more
buds that will develop into most of the
aboveground portion of the composite plant.
Budding – A type of
grafting where the scion consists of a single
bud and a small section of bark.
– Meristematic cells found in association
with the vascular tissues of stems. For
success in grafting, the vascular cambiums of
the stock and the scion must be placed in
contact with each other.
graft plants for a number of reasons.
To perpetuate clones
that do not propagate well by cuttings or
other asexual propagation techniques.
To obtain the
benefits of certain rootstocks for insect
resistance, disease resistance, dwarfing, and
tolerance of unfavorable growing conditions.
To change the
cultivars of established plants by
To produce special
growth forms such as “standards” and
To repair damaged
trunks of trees.
To study plant
development, physiological processes, and
To hasten the
reproductive maturity and fruit production in
fruit breeding programs.
Brief History of Grafting
no one really knows when people first started to
graft plants, a good guess would be that our
ancestors mimicked what they observed in nature.
Natural grafting occurs regularly. Branches and
especially roots of woody trees and shrubs, when
held in close contact for prolonged periods of
time, will graft. As the stems or roots expand in
girth over time, the bark between them is crushed.
Cambial contact is made, and a connection between
the separate vascular systems differentiates.
Chinese were grafting plants by 1560 BC. Both
Aristotle (384-322 BC) and Theophrastus (371-287
BC) wrote about grafting on a level suggesting
intimate knowledge of the techniques and results.
Aristotle wrote, “Grafting
of one on another is better in the case of trees
which are similar and have the same proportions”.
That advice on graft compatibility is still good
today! During the reign of the Roman Empire,
grafting came into common horticultural use. Paul
the Apostle discussed grafting “good” olives
onto “wild” olives in Romans 11:16-24.
the Renaissance, many plants were brought back to
Europe, and were in many cases maintained by
grafting. The need to match the cambiums of stock
and scion was realized by this time, but of course
a real appreciation of meristems was hundreds of
years away. An understanding of plant circulatory
systems developed in the 1700’s and the
formation of graft unions were the subject of much
research. By the 1800’s over 100 different
grafting techniques had been described, including
those that are in wide use today. Many of these
techniques have remained unchanged over all that
of a Graft Union
Formation of a Graft Union
order for a graft to be successful, meristematic
tissue must develop between the stock and scion,
and differentiate into vascular tissues (xylem and
phloem). Initially, undifferentiated “callus”
cells grow from the vascular cambiums of the stock
and the scion. These cells form a callus bridge
between the stock and scion and intermingle as
they proliferate. If the cells are incompatible,
this intermingling does not occur and the graft
fails. If the cells are compatible, this bridge of
callus differentiates into vascular cambium and
vascular tissues. The vascular connection between
the stock and scion allows for the translocation
of water, mineral nutrition, carbohydrates and
other metabolites. Well-formed graft unions are
structurally sound, and are no more likely to
break than other portions of the stem.
relationships are good guides to graft
compatibility. The closer the genetic backgrounds
are between the stock and scion, the better the
chances of success.
species within a genus
genera within a family
families within an order
considerations on graft compatibility include:
Monocots, in general, are not good candidates for grafting. The scattered vascular bundles in their stems are difficult to match between the stock and scion. In contrast, grafting success is common amongst dicots and amongst conifers. Their vascular tissues and vascular cambium are arranged in easily discernable rings.
few families are very compatible, with good
grafting success amongst diverse species
within families. Examples: Cactaceae,
Rosaceae, and Rutaceae.
any two cacti can be successfully grafted, and
produce some interesting forms. Cactus enthusiasts
plants severely rotted or diseased, by
grafting the remaining healthy portion of the
plant onto another cactus.
better growth and flowering by grafting scions
of slow growing species onto vigorous,
unusual growth forms.
especially in Japan and Europe, have used grafting
to bring unusual growth forms of cacti to the
market. The most common of these novelty cacti are
the “Moon Cacti”. With brightly colored scions
of red, orange, yellow, or white atop green
stocks, the “Moon Cacti” are quite striking.
The sources of the colored scions are mutant
seedlings lacking the green chlorophyll pigment.
These seedlings would not live by themselves for
more than a few weeks since the absence of
chlorophyll prevents them from making food by
photosynthesis. As tiny seedlings they are grafted
onto vigorous green stocks, which provide the
materials to support the colored scions. These
“Moon Cacti” grow for years, but when the
green tissues of the stock begin to cork over from
old age, regrafting to a new stock is necessary or
the scion will slowly starve to death.
Interestingly, many people think that “Moon
Cacti” are giant, brightly colored flowers. In
reality, they are just brightly colored stems.
Cactus grafts made between green scions and green
stocks are much more vigorous than the “Moon
Cacti”, and can live indefinitely.
simple technique for grafting cacti follows:
a sharp knife, cleanly cut off the top of a
small, upright cactus, several inches above
the soil surface. This will be the stock. A
plant growing in a three-inch pot, with a
one-inch diameter stem would be ideal.
a small (approximately one-inch diameter),
spherical stem from a barrel cactus, and
cleanly cut it across the bottom. This will be
the scion on top of the stock in such a way
that at least some of the vascular cambium of
each part is in contact. This may require the
scion to sit atop the stock a bit off center.
The vascular cambium region can be readily
seen as a distinct ring on the cut surfaces of
the stock and the scion.
two rubber bands of appropriate size, and
affix them over the scion and under the bottom
of the pot. They will exert a steady pressure
on the scion, pressing it against the stock.
The two rubber bands should go over the scion
at 90 degrees from each other, in order to
prevent the scion from shifting. Rubber bands
that are too loose will not hold the scion
tight enough. Rubber bands that are too tight
will cut through the scion.
the plant as you would any other cactus.
a month or two, remove the rubber bands. The
scion should be firmly attached to the stock.
the graft union failed to knit, cut a new
surface on the stock, prepare a new scion, and
try again. Practice makes perfect!
Here are 2 cacti ready to be grafted. The potted plants will be stocks. The scions will be the small stems next to the stocks.
|The stocks and the scions have been cut with a clean, sharp knife.|
|Note the vascular rings in this view of the prepared scion and stock. The vascular cambium is located in the ring. When put together, the rings must be in contact. In these specimens, the vascular ring of the stock (right) is wider than that of the scion (left). In order to match up the vascular cambiums, the scion should be set slightly off center on the stock.|
|The scions are held tightly in place with appropriate rubber bands.|
|This is what your grafted cactus should look like a year later.|