Nature in its own way has some drastic extremes, and it is actually quite
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 withstand
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 cuttings always
seem to root late and some die for no obvious reason. Production
gardeners should be quite firm about getting rid of the slow rooters because
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.

Old Stock

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 of cuttings.

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 other's light.

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 and
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 moisture loss.

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 the stems.

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 grow tubes.

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 stay strong.

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 or two.

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.