Read the regular books on cutting techniques and take the
best ideas from
each. The book, "The Best of the Growing Edge," has
a very good article Ion the rooting of cuttings.
Nature in its own way has some drastic extremes, and it is actually
amazing how much abuse plants can handle. Plants can stand some
human abuse and will grow if the damages are fixed quickly. They
seem to grow in
spite of what humans do to them. This is why mother plants can
the snipping for clones.
Most methods for cuttings will work well. One always does one's
best to create uniform cuttings when taking clones. However, some
seem to root late and some die for no obvious reason. Production
gardeners should be quite firm about getting rid of the slow rooters
they never catch up to or yield as much as the faster rooters,
no matter how hard one tries to nurse them.
The rooting of cuttings should be about 90% successful. The real
secret lies in the ratio of roots to plant. A cutting with many
good roots will
keep this ratio as it grows bigger, and this keeps the plant ahead
all of its life.
Shoots should be growing vigorously and have enough stored energy
before they are cut from the mother plant. Once a shoot has hardened
into wood, it is almost incapable of producing roots.
Choosing Big or Small Cuttings
Despite the fact that plants can stand up to some human abuse,
the rooting of cuttings may not always be successful. One can
increase the success rate of the rooting by controlling the size
For production growing, small cuttings do have the advantage.
One-inch cuttings with only 2 or 3 leaves and all other leaves
removed are very energy efficient. This is because big leaves
tend to be net energy consumers. The advantages of smaller cuttings
are that they will not wilt quickly and they will not consume
the energy within themselves as quickly but will remain green
as the roots are starting to form. As well, the cuttings - if
small - can be spaced more closely and not interfere with each
As explained at the beginning of this chapter, the main factor
to achieving a successful plant is the root to plant ratio. The
small plant with a high root to plant ratio is the best producer.
Growth Regulators for Root Callus Formation
Most cuttings have enough auxins in them for root development
but it takes time for their own auxins to move down from the top
to the cut end. Therefore, synthetic growth hormones like rooting
gels and powders are applied to cuttings to supplement the plants'
own auxins and to give them a head start.
Once the cuttings are placed in the growing medium, their stem
cells have to develop calluses which then form the new root cells.
There is a delicate balance between auxins for root development
and cytokinins for shoot development that promotes this callus
formation. Therefore, be careful when rooting NOT to mix all the
wonderful advertised growth regulator products together because
if that delicate balance is upset, disaster happens.
As well, rooting mixes containing IBA (auxins) must be used sparingly
and limited to a brief time because as the actual roots start
to grow out of the callus tissues, the auxins may promote more
callus growth and actually slow root development. Sometimes the
roots only really start to grow well after all the rooting powder
has gone. Using less is better.
Some rooting compounds are #1 - #2 - #3, and they contain 0.001
% 0.004% - 0.008% active ingredient. Which one to use depends
on how much auxin is naturally in the plant already. Since using
too much auxin on cuttings will slow growth, try each product
to see which does best for the plants you have. Some rooting gels
have a fungicide added, and this is probably of further benefit
to the cuttings.
Nutrient for Cuttings
It is recommended that NO NUTRIENT be added to the growing medium
for cuttings until some roots have started to show. One reason
is that the cut stems have difficulty drawing water against the
salts in the nutrient. Another reason is that the nitrogen in
the nutrient also work against plant hormones.
Tests show that nitrogen tends to divert growth from the roots
to the top of the plant. Conversely, the lack of nitrogen causes
roots to grow quickly and the top to branch less. The mechanism
that does this is interesting: with low nitrogen, the fast growing
roots divert the growth hormone auxins away from the top down
to the root tips. This is good because in the beginning stages
one wants not top growth for cuttings but root growth, which will
increase yield at a later stage.
Foliar feeding of cuttings on average did not produce any more
roots than did cuttings sprayed with good natural water. This
is because only after the node cells on the cuttings have differentiated
and have some actual root cells, can the plant again process nutrients.
Vitamin B1 can be used to alleviate plant stresses (ie. transplanting
plant damages due to environmental extremes). Some companies
recommend using Vitamin B1 to assist plants to root. One application
is on fresh cuttings: just use pure water with a measure of Vitamin
B1 until roots appear, then start with a Weak nutrient mix. There
are methods for rooting cuttings without Vitamin B1, but if you
decide to use the product, follow the manufacturer's directions
for applying on your plants.
When adding plant nutrition, note that the pH range for nutrient
required around rooting cells for maximum nutrient uptake should
be pH 5.2 - 5.8 (Experiments in Plant Tissue Culture, Third Edition,
by John H. Dodds & Lorin W. Roberts, England 1995: University
of Cambridge Press. ISBN 0-521-47313-6).
Light period for cuttings
Plants have a free running internal bio-rhythm of
21-27 hours. In this rhythm, they need dark time. Cuttings have
a built-in daily rhythm that they inherit from their parent. Cuttings
will root better wit~ a 6-hour to 8-hour dark period because this
is the main time when the leaves and the stems transfer energy
down to the root zone for storage and growth.
Look at the graph below and see that maximum rooting took place
at 16 hours of light. This experiment was done on a particular
plant, but the general principle holds good.
Light Level for cuttings
After many years of experiments, it has been established that
most cuttings do best with light levels between 500 -1,000 lumens
(read about Light and
Photosynthesis). However, very low light levels do not create
enough photosynthesis to allow the plant to store much energy.
This is why one should allow about 3 leaves on each cutting; more
than three leaves tend to take more energy than they provide.
At these lower light levels, fluorescents are
very good to use on cuttings. Use 16 hours of light in a 24-hour
cycle because the plants have to build up a sugar reserve to last
them through the hardening-off period.
Relative Humidity for Cuttings
The cutting has only a very thin layer of wax built-up on its
cuticle (the outer protective layer of the leaf). The slower the
hardening time of the cutting, the better, because the plant can
dry out and wilt very quickly in this period. Artificial wax sprays
are available to help the plant if required.
Humidity around the cuttings of anywhere above 70% is good. As
mentioned, artificial wax sprays on the plants can help to reduce
A Rooting Technique
Using rockwool cubes is one of the easiest and quickest ways
to root cuttings. The size of the cube does not matter at all,
since all you need is something to hold the cutting upright and
keep the cut end moist. Using the smallest rockwool plugs (144
per tray), soak the cubes in nothing but pure water at pH 5.8
(read about pH and Water ). Note here that city water can contain
chlorine, but it is not sufficient to upset the plants as it is
also a trace element for them. Leave the cubes soaking while you
are getting ready. (* If you wish to use Vitamin B1 to assist
the cuttings to root, follow the directions on the product label
for its application.)
Cleanliness is everything. Total cleanliness and rubber gloves
are what it is all about. One sometimes does not appreciate how
powerful "the bugs" are because a person's immune system
is fighting infections every second of the day. In an experiment,
chickens raised in a completely sterile tent grew to be 30% bigger
than the control group. This shows similarly just how much energy
humans and plants expend in fighting off infections. Remember
also that plants waste energy fighting any "bugs" humans
may put on them. Therefore, always wear rubber gloves and keep
your scissors sterilized in alcohol; do not use unsterilized containers.
As well, plants have natural bacteria in their stems, and these
soon multiply at a cut site and block off water and nutrient.
With cuttings, use a rooting
gel with an anti-bacterial in it to stop these bacteria from blocking
Always keep your mother plants with fresh vigorous shoots. To
start, snip a vigorous shoot longer than you will need and place
the snipped end of the cutting in a bowl of water to stop air
from entering the stem and to keep the leaves pumped up. Cut all
you need at one time and place them in the water.
Studies show that a cutting made immediately above the node (a
node is where a leaf or bud joins the stem) grew more roots than
one taken immediately below the node. This is because the actual
internal node material (immediately below the nodes) takes longer
to differentiate into root cells than the actual stem cells (immediately
above the nodes) or the cells of a growing bud site. A compromise
is recommended as shown .below. Try to cut at least 1/4 inch below
the node. On small softwood cuttings, a straight crosscut is best.
On older, semi-hard wood stems, a diagonal cut is better.
Next, place the pre-soaked rockwool cubes in growing trays. Get
the rooting gel or powder ready. Lift each cutting, snip it as
shown in the diagram above, dip it into the rooting compound,
and place it firmly in a cube hole. Do not force the stem through
the bottom of the cube. Remember to keep the first set of leaves
very close to the surface of the medium so that the plant does
not develop a long useless stem as it grows.
When you have filled the trays with the cuttings, place clear
tray lids over them. Then, put the trays under full-spectrum fluorescent
Placing the trays on a plant heating pad set to 80°F (26.7°C)
will reduce the rooting time considerably. Do not go much beyond
that because too high a temperature (over gO°F or 32.2°C)
can injure the roots. Take care also not to sit the trays directly
on the pad. Rather, put a blanket between the trays and the heating
pad; otherwise, when the thermostat clicks on, the localized heat
can injure the roots.
For the first week, the moisture in the cubes and the trays is
sufficient. By the second week, the trays will start to feel light-weighted,
and it is now time to add more water. However, never add too much
water, and there must never be any standing water or the roots
will drown. For this method, never use anything but pure water
until the roots appear.
The aim here is to start driving the roots of cuttings as soon
as they have I
started. The sooner the roots are forced to produce the better.
If the roots are forced from the beginning, they grow strong and
To separate the slow rooters from the production plants, do not
wait until the cuttings are showing long adventitious roots underneath
the cubes. Instead, after about a week depending upon the type
of plants, gently open one small plug cube and see if the node
has started to put out the first true white root shoot. Check
it each day. The roots usually appear in about 14 days. When they
do, harden them off very gently and gradually over the next day
When you find that the majority of the cuttings have started
to put out small adventitious roots, start to harden the plants.
Crack the lid about 1/4 inch for the first day and 1/2 inch on
the second day. Then, remove the tray lid totally.
At the start of the next light period, spray the cuttings with
cytokinins and they are ready to have increased light. Put the
plants under a 400-Watt or
11,OOO-Watt HID lamp. Within 3 days, the roots should be out seriously
looking for food and water. Around 10 to 14 days, they should
be ready for production.
Another Method for Rooting Cuttings
The fertilizer companies have a product out which is for "transplanting."
It has a general mix of low nitrogen, high phosphorous, low potassium,
and a trace of auxin growth hormone. Mix up a nutrient solution
as shown on the label and soak the rooting medium in it.
With this method, do not use rooting gels or powders because
the extra auxins can stop fast rooting. Just put the cuttings
directly into pre-soaked rockwool cubes and add 1/4 inch of the
nutrient to the plastic tray. Cover the tray with a transparent
lid. Place the cuttings under about 500 lumens of light, and do
not touch until nice long roots can be seen sticking out. Be patient
- some plants can take as long as 3 to 4 weeks to root.