Categories of cuttings.
For the home owner the above can be as simple as keeping the cuttings under
the bonsai bench (But off the ground) that is watered once or twice a day
where they will receive no direct sunlight. The next step up is to build a
propagation case and provide it with automatic mist. The first case I built
was eighteen inches wide by about six feet long and two feet high and
covered with clear fiberglas. It held three or four flats. It had three mist
nozzles overhead (available from mellingers for about a buck apiece). I am a
great tinkerer which gets me in trouble but I have a lot of fun designing
and building stuff. I built my own mist system and put heating cables in a
bed of sand in the bottom. I built my own 'leaf type' mist switch that opens
a circuit when wet, it is counterbalanced and drops when wet opening the
contact on a microswitch, and rises when dry closing the circuit and kicking
in a solenoid allowing the water to flow to the misters. Commercial units
are available for about $150. Mine never did work right and I was always
frying cuttings. I now use timed mist, as do most professional growers. You
can now get these from Charlies Greenhouse supplies, they are about $75.
They are timed periodic mist, so you can vary the period between mist and
the duration of the mist. For our climate I find seven seconds of mist every
fifiteen minutes sufficient to keep the leaf surfaces constantly wet. Mine
is in series with a 24 time clock that is programmed to turn it off during
the night. It can still be too wet on cloudy days so I also have it in
series with a themostat that does not allow it to come on unless the
temperature is about 72 degrees F. In a propagating case leaving the doors
cracked open will allow sufficient air for ventilation.
Bottom heat acts a stimulant for the production of roots as well as for
faster root growth. In general bottom heat should be ten degrees hotter than
the ambient air temperature, although any amount of bottom heat is useful. I
have mine set on a themostat that turns it off during the day when it is
over 75 in the propagating room to save propane. The temperature should not
be allowed to fall below sixty five and optimal seems to be about 75 ot 80
for most species. Some species are more sensitive to heat than others. Most
of the tropicals I have grown in the past, liked it hot. Maples also root
much faster when hot. It is thought that a few cultivars of Juniperus
actually prefer cooler temperatures once they callus, but the jury is still
out on that one. I have had Fuchsia root in five days on high heat,
pomegranate in seven to ten. I even had some Japanese Maples begin to root
in ten days last year.
The easiest and cheapest way for the homeowner to get into bottom heat is
by purchasing a heating mat and controller, you can get a small system for
about one hundred bucks. They use a lot of electricity, even a small one, be
prepared for your bill to jump. Larger systems are hot water fed. A regular
hot water heater can be used with a small circulation pump hooked to
thermostat. Commercial units are called Biotherm and manufactured by a small
company here in California. I designed and built my own with drip tubing
parts. It has worked fine for eight years.
By far, most semi hardwoods require hormone in the range of 0.3% to 1.6%
IBA, or Hormex 3 to 16. There are some that require no hormone such as
willow, Salix, although I shallow dip my Salix species now and start them
flats instead of water. They begin rooting in less than a week and are ready
to transplant in two to three weeks. The root systems are denser and more
fibrous with hormone treatment. Some cultivars of Japanese Maple, Acer
palmatum, require high levels of IBA, I am now using shallow dips in Hormex
30 (3% IBA) for some of them. Many species will not root immediately,
although most root over four to ten weeks. Some species will take a year or
more to root after initially callusing in a few weeks. These I take off the
heat at the end of the season and keep shady and cool until they do root.
Hawthorns and many Chamaecyparis fall into this category.
Many semi hardwoods respond favorably to wounding. The bottom of the
cutting is sliced thinly through the cambium for about an inch, taking out a
sliver of bark without removing much wood. This is best done with the edge
of sharp shears or a sharp knife to make a clean cut. This provides a
surface for callus and hopefully root development. It helps Malus, Acer, and
roses. It is also interesting to watch where roots develop on various
species. If you wound, the roots will often form in a line along the callus
tissue. Many cuttings form in a ring around the bottom of the cut
(Chaenomeles), others form at the lenticels (openings in the stem similar to
stomata on leaves), and yet others form at the leaf scars (roses). For some
it is necessary to have a node at the bottom of the cut, other not
(Clematis, Acer).
Well, you can see that I like to do cuttings, actually this is the
specialty of our nursery, and we are doing some things that very few people
people in the world are doing such as Hawthorns and Birches. Probably more
than you ever wanted to know, but a nice diversion for me on a hot sunday
morning when I am supposed to out there doing......CUTTINGS!
Evergreen Gardenworks is a mail order nursery. To receive their catalog
just send your name and snail address
to PO Box 1357 Ukiah CA 95482 or request it via email bonsai@pacific.net.
P.S. Clean! To avoid fungal infections, a very serious problem with
cuttings keep everything as clean as possible. Think of it as handling meat
in the kitchen. You must always remember where those hands have been. Use a
ten percent bleach solution (nine parts water, one bleach) to clean
everything including the flats, shears, your hands and the cuttings. After
the cuttings are made soak them in the bleach solution for fifteen to twenty
minutes, rinse all of the bleach off thoroughly (it will oxidize the IBA)
and dip in hormone and stick.
Rooting Medium
The medium must be sterile for good rooting percentages over a wide range
of species. Some species appear to immune to everthing fungal in the soil
(willows) and others are very prone to infection (Mediterranean climate
plants in general, daphne). Most roots also need air to form as well as to
minimize infection. You must balance the need for drainage against the need
for a constant supply of moisture. Without automatic mist the medium must
hold more water. A good place to start is 50% peat and 50% perlite. With
automatic mist or in an environment of cool moist air such as a coastal area
it is better to move closer to all perlite. Perlite is now nearly
universally used instead of sand or volcanic aggregrate because it is
lighter, sterile, and inexpensive. I use about eight parts perlite to one
part peat and one part vermiculite. The peat and vermiculite make the
perlite easier to handle, reduce the fluffiness and aid in punching the
holes for the cuttings. I also harden off and grow out the cuttings in the
propagating flats so the peat and vermiculite give me a small amount of
nutrient holding capacity, perlite has none. I use 18 inch square
propagating flats with mesh bottoms that give excellent drainage but still
hold the medium inside. The mesh is about half inch squares. Ground covers
are frequently grown in these flats. I use a dibble board that I made to
punch the holes for the cuttings, 182 per flat. All of this is old fashioned
these days with the advent of Oasis type cells, but for me it is cheap and
easy and allows me to keep the rooted cuttings in the flat longer.Rooting Hormones
There are two types of rooting hormones on the market, talcs and solutions.
Talcs such as Hormex contain the hormone indolebutyteric acid, IBA at
various concentrations, that's what the numbers mean, Hormex #1 is 0.1% IBA.
Rootone is 0.1% IBA and also contains another hormone (I think, I don't use
it) NAA, napthalenic acetic acid. The spellings are probably wrong, my
chemistry is getting a little rusty. Rootone also contains a fungicide,
Thiram. Rootone is fine for easy cuttings but will be worthless for cuttings
needing a high level of IBA. The liquid hormone solutions such as Dip and
Grow and Wood's are a solution of IBA and NAA in alcohol. The alcohol acts
as a carrier so lower concentrations can be used. Both are only 1% IBA at
full strength. Some cuttings are sensitive to alcohol and can burn. I have
found the solutions not effective for cuttings requiring how levels of
hormone. How do you know what levels for each species? There is one book
that is far superior to all the others for this type of encyclopedic
information, Propagtion of Woody Plants, by Dirr and Heuser, available from
Timber Press, they have a Web site. It costs about $40. It is my propagating
bible, although I know most of it by heart now. It is a compendium of
studies from around the world including the information compliled by the
International Plant Propagators Society, IPPS. If you have only one
propagating book it should be this one. Beginners will find it only slightly
overwhelming at first.Moisture
Without a root system cuttings rely on absorbing moisture through the stem
and leaves. This works just fine if the medium is constantly wet and the
humidity is high and it is cool, seventy to eighty degrees during daylight
hours. This is the toughest aspect to achieve at home. You must reduce the
rate of transpiration to protect the cuttings from wilt. You can do this by
keeping them cool, keeping the leaf surfaces wet, and by reducing the leaf
surface area. You can remove some leaves to reduce surface area so that only
two or three small leaves remain, or you can, as I prefer, remove the bottom
leaves then cut the remaining leaves in half. After a while you get a feel
for how much leaf area each species can support given your individual
conditions.Sufficient Light
It is thought that roots are stimulated in cuttings by high light levels,
although I have not seen the studies to support it. But cuttings do root as
a response to food moving down the stem in the phloem (remember your botanty
test, phloem and xylem) and stopping at the bottom cut. Finding no roots to
store the food, it backs up at this point and changes take place in the
presence of hormones to convert stem tissue to undifferentiated tissue
(callus) to finally root tissue. This works better of course if there is
sufficient food to make this happen, thus the need for retaining leaves on
softwood and semi hardwood cuttings. Food is also stored in the stem tissue
itself, and this is sufficient for leafless hardwood cuttings, although the
process is much slower. High light levels obviously play a role here by
keeping up photosynthesis. You must balance out the need for light against
the buildup of heat. For simple systems all shade works just fine. A VERY
light foliar feeding also seems to aid in this process, although nitrogen
encourages algae to grow in the medium and will soon create a wonderful
swamp if you overdo it. Bottom Heat
Automatic mist and bottom heat revolutionized the nursery industry around
the time of the second world war. Before that most production was by
hardwood cuttings, which was slow and effective for a limited number of
species. These days there are very few plants that cannot be propagated from
cuttings and those that can't can usually be done by tissue culture.Categories
Cuttings fall into three categories, 1)softwood, 2) semi hardwood, and 3) hardwood.
Softwood Cuttings
These cuttings are taken from new growth at the succulent stage. When a
turgid plant tip snaps when bent at ninety degrees it is ripe for softwood
cuttings. Most perennial cuttings are done this way, very few woody plants.
In general low levels of IBA improve rooting but are not necessasry. I find
that Hormex #3 on the very bottom of Fuchsia cuttings, not more than 1/8
inch stimulates incredibly dense roots starting in about one week. This
would ordinarily be too strong for this type of cuttings and there is some
necrosis where the cutting was actually dipped, but roots are amazing.Semihardwood Cuttings
Most woody plant cuttings these days are from semi hardwoods. We are in the
peak season right now. These cuttings are taken from wood that grew this
year but is now firm and hard, with hardened leaves. It is well lignified at
the base but still may have a soft tip that may or may not be removed. It is
better to go by the feel of the wood instead of the calendar. There are also
infinitely varying degrees of hardness and each species and sometimes
cultivar will respond differently. This is a matter of experience and
volumes have been written about it. Some species such as birch and Picea
have very narrow windows of opportunity. Others, such as most crabapples can
be taken all summer long.
Hardwood Cuttings
Hardwood cuttings can be taken at any time of the year, but are usually
taken late in the season or winter and stored in sand, sawdust, etc. They
are cuttings from wood that has gone through an entire season of growth. The
can be treated just like softwood cuttings in summer for some species, but
most are done at the end of the season and either stored and planted in the
spring after they callus or simply planted in open ground in the winter.
With the advent of mist and bottom heat their popularity has diminished
except for some commercial crops such as grapes.
About the Author
Brent Walston
Evergreen Gardenworks