Taking the cuttings

What are auxins?

They are one of the groups of plant growth regulators (hormones). Some auxins are artificial compounds, but many are produced naturally by plants, especially in young growing parts of the shoot. In nature, they move always from the tip towards the base of shoots, but when applied at the base of cuttings there can be some movement in the opposite direction.

What do they regulate?

Auxins control many different aspects of growth and development, as is typical of plant hormones. For instance, they are known to influence the elongation of stems and leaves, the setting and ripening of fruits, and the growth in thickness of trees. They also stimulate the formation of new root tips in stem cuttings.

-=no auxin; +=IBA and NAA mixture.

What kinds of auxins are best for rooting cuttings?

Two artificial auxins, known as IBA and NAA, are most commonly used, either singly or mixed together (see A 63 for the chemical names and sources for auxins). Several other auxins are available, but turn to them only if you draw a blank with IBA, NAA and IBA/NAA.

How are they applied to the cutting?

There are three main methods:
Method 1 - Quick dip: dissolve the auxin in alcohol (or another organic solvent), dip the basal few mm of the prepared cuttings for 1–5 secs into the solution and let the alcohol quickly dry off before setting them. (Note: If left in alcohol for more than a few seconds, the base will die!)
Method 2 - Powder (talc): Buy a commercially prepared auxin rooting powder, put the basal few mm of the prepared cuttings into the powder, gently tap to remove excess, and set at once.
Method 3 - Soak: dissolve the auxin in water, and leave the prepared cuttings standing with the basal 2–3 cm in the solution for 4–12 hours before setting them. (Note: Many auxins are slow to dissolve in water.)
With the ‘bubble-bath’ system, the cuttings remaining with their bases in water, which is kept aerated (as in a fish tank). Small quantities of auxins are dissolved in the water to assist the rooting.

Which is best?

Method 1 has been generally found to give the best results for commercial nurseries producing woody ornamentals in the USA. Advantages include the correct amount of auxin actually entering the cutting, dissolved in the alcohol, and roots forming higher up the stem. (For research treatment, see A 45.)
Method 2 can be convenient:

1. for preliminary trials;
2. if there are no facilities for weighing out auxins; and
3. before staff and workers have been trained.

Some rooting powders also contain a fungicide (A 52, A 63), which helps to discourage disease.
Method 3 is a stand-by in the few species that are intolerant to alcohol.

What are the disadvantages?

Method 1: the alcohol evaporates during use, making the solution more and more concentrated. (Can be solved by using 50/50 alcohol/water, using only a little auxin solution at a time and closing the container with the thumb, and having a good production line of prepared cuttings.)
Method 2: easy to get too much powder on the base of the cutting (which can sometimes stop the outgrowth of the new roots), and the powder loses its effectiveness if not kept dry and in a refrigerator.
Method 3: difficult to use with larger numbers of cuttings, and sometimes the leaves may wilt during treatment.

How strong should the auxin solution be?

A useful start can be to use IBA at a concentration of 2.5–5.0 grams/litre (= 2500–5000 parts per million, or a 0.25–0.5% solution), or alternatively a 50:50 mixture of IBA and NAA. The best auxin and concentration varies from one tree species to another, but can be found out by experiment (see A 45), or by trial and error. Research suggests:

2 g/l IBA for Triplochiton scleroxylon, Vochysia hondurensis and several other tropical tree species;
a range from 0.5–4.0 g/l IBA for Albizia guachapele;
4 g/l for Cordia alliodora and
10g/l IBA for Khaya ivorensis.

Note: too strong an auxin treatment can discourage the roots from emerging from the stem).

Do all tropical trees respond?

Most do so, but no clear differences in rooting were found in several experiments with Lovoa trichilioides.

Supposing I haven't any auxins?

You can still root cuttings of many kinds of tropical tree. Rooting will probably be slower, so concentrate on getting the propagation conditions as favourable as you can (A 30–35). See A63 for sources of auxins.

What do the auxins actually do?

They often:

1. make cuttings root more rapidly;
2. stimulate more roots on each cutting;
3. lengthen the zone in which roots are formed, giving a better root system.

Sometimes they can:

4. turn a very hard-to-root species into a rootable one;
5. change the type of root produced, for instance by favouring the rather thicker roots which produce the tree's structural root system.

Where should I keep the auxins?

They don't keep well at room temperature in the light, so store all auxins in a refrigerator at 5–10°C.
Provided they are kept dry as well as cool, pure auxins can be stored for several years, and powders for about a year. (Note: in the humid tropics, allow the container to warm up for 30 mins before opening it, to avoid getting the contents wet). Solutions of auxins keep only for a week or so, even in the refrigerator.

Why should I trim the leaves?

It is important for leafy cuttings of species with leaves longer than about 8–10 cm. Experiments with Triplochiton have shown that rooting is better when the leaf-blade is neither too big nor too small.

Why is this so?

Large leaves may lead to more loss of water by the unrooted cutting. On the other hand, small leaves may not produce enough sugars and other substances needed for the cutting to survive. Trimming also makes the cuttings easier to handle, take up less propagation space and be less likely to rot.

What is the best size?

This varies from one tree species to another. Aim for a total area of about 50 cm², except for the mahogany family (Meliaceae). The best size is also influenced by the type of cutting, auxin application used, propagation environment, etc, so it may be worth doing a trial (A 45).

Does the shape matter?

Not very much. With leaves shaped like a hand, it is easy to cut off the ‘fingers’ of the larger leaves, and with compound leaves to take off some of the leaflets. If insects have eaten part of the leaf, leave more of the rest. For small-leaved species try multi-node cuttings (A 42), with more than one leaf above the rooting medium.

What is the best way of trimming the leaves?

With a sharp pair of scissors, avoiding crushing the leaf tissue.

When should the trimming be done?

Trim before the shoots are detached from the stockplant. This will reduce water-loss (A 34 & A 42), and avoid extra bulk in the polythene bags used for carrying the cuttings. However, if a few leaves are missed, they can be trimmed while preparing the cuttings (A 43). If leaves can be trimmed the day before, this will allow the propagation to start early.

Should I trim all the leaves on the stockplants?

No, only those which are on wood suitable for cuttings (see A 6). In any case, at least two good basal leaves should be left on each shoot, except where it is to be heavily pruned (A 25).

What about non-leafy cuttings?

It is often best to take shoots that have already lost their leaves naturally. If there are leaves present, most should be cut off (best to do this at the top of the leaf-stalk), and the topmost one or two can be reduced to about 1–2 cm in length (A 4).

What needs to be ready before I start?

1. The poly-propagator (or mist propagation area), with shading (A 33), water in the bottom of the propagator (A 31, A 34, A 50) and preparing of the rooting medium (A 35) all done;
2. A moist, shady workplace near the propagation area, with tools and materials ready for preparing the cuttings (A 43) and applying auxins (A 40);
3. Labels, pencil and record sheets ready (A 64, A 66–67); as well as polythene bags, ties and a fine water sprayer (or other supply of clean water);
4. Except in species with small foliage, the leaves that will left be left attached to each cutting should already have been trimmed to around the optimum size (A 41).
   (Note: Get everything ready, so that the cuttings can be kept moist and set in the propagation bed (A 44) without delay.)

How big should the cuttings be?

As a rough guide, aim to take moderately vigorous shoots that will cut up into cuttings that are 2.5 – 12 cm long, with a stem diameter at the base of about 4 – 8 mm). If possible, avoid thin shoots making little or no new growth; and thick very vigorous twigs, although rapidly growing young coppice shoots are fine before they become too woody. (Non-leafy cuttings are often larger - see A 4).
Also important is the number of nodes in a cutting, which will depend on the growth habit of the tree species, how the stockplants have been managed and whether you have plenty of material or not.

How many nodes should my cuttings have?

1. Single-node cuttings give larger numbers of cuttings from limited amounts of material. Provided that the internode between successive leaves or leaf-pairs is more than a minimum of 1.5 cm, cut just above each node that has both a leaf and a bud.
2. 2 or 3 node cuttings are suitable for shoots with shorter internodes, those which lack leaves or buds and for species that are harder to root. Cut just above nodes which do have a leaf + bud, and just below a node, because stems often root better at the nodes.
3. Many-node cuttings are best for species with minute leaves and very short internodes, for example Casuarina, Cupressus. They are best taken 5 – 15 cm long.
4. Split cuttings are occasionally used where there are two buds at each node. In robusta coffee, for example, two cuttings are often made out of one by splitting them down the middle.

When should I take the shoots?

Early in the morning, preferably in misty weather or just after rain. This will keep drying out to a minimum (A 34).

How should I take them?

1. open a polythene bag, moisten the inside and put in a label with the clone number (A 11), and also write it on one or two leaves with an indelible marker;
2. cut the shoots from the stockplant with a sharp pair of secateurs or knife, and place them in the bag. Keep it closed and in the shade!
3. as soon as a bag is completed, spray the shoots lightly, close it with a tie, and attach a second label with the clone number and estimated number of cuttings;
4. take the bags to the propagation area as quickly as possible. (Keep them in the shade and avoid closed vehicles that may overheat in the sun).
   Also avoid piling up or throwing of bags, or the shoots may be damaged. Tests have shown that when trees have been jolted, they often grow poorly. To reduce crushing and bumping of shoots, support the bags in separate boxes or with elastic cords.

What sort of polythene bag is best?

Any kind will do, but the best are of a new type that are white on the outside and black on the inside. The shoots inside are kept much cooler because the white surface reflects heat, while the black one radiates it away. If these are not available, try making double bags yourself by cutting and stapling sheets of black and white polythene.

How long can cuttings be kept before setting them?

The sooner you can set the cuttings the better (see A 44). However, avoid opening polypropagators in the middle of the day, because the humidity inside immediately drops. So plan to set your cuttings before 10 am or after 4 pm. Leafy cuttings of Triplochiton scleroxylon will not keep in bags more than 2 nights.

Why shouldn't I set the cuttings immediately?

It is very important to avoid delay. However, the shoots first have to be divided up into cuttings, and there are usually other things to be done before they are set. These include:

1. Re-cutting the base;
2. Applying auxin;
3. Removing unwanted material;
4. Treating against pests and diseases.

How do I re-cut the base?

Make a new clean-cut base to the cutting, using a very sharp knife or scalpel blade; in order to

1. remove wood that has been split or damaged by the secateurs, which might rot;
2. shorten cuttings that are too long;
3. cut the base at a particular angle, e.g at about 90° in Khaya - if not, the root system will be one-sided;
4. cut stems where rooting is most likely (e.g. just below a node);
5. remove latex or mucilage that may stop the entry of auxins.

What about auxin treatment?

With a fresh-cut base, dip the bottom 5 – 10 mm of the cutting in rooting auxin (A 40) in order to:

1. encourage cuttings to root fast;
2. increase the percentage of cuttings that root;
3. increase the number of roots on each cutting;
   1. rooting powder - some powder should stick to the cutting, but tap off any excess;
   2. auxins dissolved in alcohol - quickly dip into the solution and dry the alcohol off rapidly (e.g. with a small fan);
   3. auxins dissolved in water - leave standing in water in the shade for several hours.

What unwanted material needs to be removed?

1. trim any larger leaves missed while trimming (A 41), and cut out any dead parts;
2. remove leaves at lower nodes, but always leave at least one at the top;
3. take off side branches that would be below ground;
4. in trees with two leaves opposite each other, take off one of the two buds to produce a plant without a basal fork;
5. throw out damaged or unsuitable cuttings (A 6).

How do I guard against pests and diseases?

If possible, avoid putting unhealthy cuttings into a poly-propagator. Where supplies are limited:

1. insects such as aphids, psyllids, eggs of caterpillars - dip the top of the cutting for a few seconds into a diluted insecticide solution (keeping the base with any auxin powder out of the liquid). Cuttings can then be set in a poly-propagator; but would need to be kept in a moist place for 20 – 30 minutes before receiving mist.
2. moulds (fungi) - treat in a similar way, but with a fungicide solution. Some commercial auxin rooting powders contain ‘Captan’, a fungicide. (See A 63 and also A 52).
   NOTE: insecticides/fungicides may be poisonous - wash your hands before eating!

What if I want the cuttings for a rooting experiment?

Cuttings should be as uniform as possible for research (A 45). If you have plenty of shoots, choose a standard size and type of cutting. If there is a limited number, grade the cuttings into different size classes before allocating equal numbers of each class to the two or more techniques or rooting conditions you wish to compare.

What should I do first?

1. Get ready everything listed at the top of A 42;
2. Check that the rooting medium is moist, but not too wet (see A 35);
3. Trim the leaves (A 41), then take (A 42) and prepare (A 43) the cuttings.

How far apart should the cuttings be?

So that they don't touch each other, but with no wasted space.

How do I put them in?

Make a hole with a small stick (not too deep, and about the same diameter as the cuttings), put in the cutting and make the medium firm around it.

Won't the cuttings dry up while they are being set?

Yes, unless you are careful to:

1. keep them always in the shade;
2. leave most cuttings inside a polythene bag while you are working;
3. use a fine spray of water from time to time (A 34);
4. open lids of poly-propagators only enough to work, and close them immediately you have finished.

Should the cuttings be in rows?

Rows are much easier, for several reasons:

1. the separate clones are less likely to get mixed up, which could cause long-lasting confusion (A 11);
2. the new root systems need not be disturbed unnecessarily;
3. there is less wasted space if rows of large-leafed cuttings are set with the leaves all pointing the same way;
4. it is easier to count how many cuttings you have set, and check their progress.

What about labels?

At least two labels are needed, one before the first cutting in a batch or clone, one after the last. Write clearly and firmly with a good HB, B or 2B pencil, not a pen.

Essential information includes:

1. the clone number;
2. the date of setting;
3. the number of cuttings set;

In research propagation (A 45), also:

4. the treatment;
5. the block; and
6. other variables, such as the origin or type of cutting, node number, etc.

This may require one label per cutting.

What else is important?

1. Cuttings with spreading leaves;
   Watch out that these don't stop water spray or mist reaching cuttings underneath.
2. Recording the production of clonal plants:
   Keep records of the origin of each batch of cuttings, and of the clones it contains (see A 66–67).
   This will allow calculation of % rooting, % survival, stocktaking and forward planning. It will also be important to be able to find the stockplants of a promising clone.
3. Research on rooting cuttings:
   Keep more detailed records, including a plan showing the layout of the experiment. Also make periodic assessments and observations (A 45).

How can I speed things up?

1. Good planning and preparation before starting:
   1. Think about how and where people should work, developing a smooth production line approach.
   2. Give each person a specific work-rate (eg. 200–350 cuttings per hour for the one just setting the cuttings)
      (Note: watch out that the work is done properly!)
2. Start setting the cuttings at the back of the propagating bed, and work towards yourself. With wide beds, start at the middle and work towards first one side and then the other.
3. For setting many small cuttings, make a template for the holes, using nails driven through a piece of plywood at the correct spacing and depth.

What's different about rooting cuttings for research?

It needs greater uniformity, comparability and care at all stages, so that valid comparisons can be made.

Where should I start?

Multiply plenty of cuttings of a few clones, and grow them as well-managed stockplants (A 24–27). In time, you should have a good supply of uniform, clonal shoots.

But surely they will still produce better and poorer cuttings!

Very true. But in any case it is a good plan to standardise or grade the cuttings for experiments (A 43), whether you are comparing two or more types of cutting; techniques; rooting conditions; or clones.

How and why do I standardise or grade the cuttings?

1. Standardising: If you have plenty of shoots, take more cuttings than are needed for the experiment, and then go through them excluding:
   (a) poor cuttings and those with unusual growth habits;
   (b) the biggest and the smallest;
   because the more uniform the cuttings, the less the variability within the experiment, and the greater the opportunity of obtaining useful results.
2. Grading: If the supply is limited, sort the available cuttings into 2–6 groups, each containing the same number of cuttings of similar size, vigour and growth habit. Then take group 1 and assign equal numbers of cuttings to each treatment, and repeat for the other groups. This is done because:
   (a) it prevents one treatment being biased with many larger or smaller cuttings;
   (b) if a note is kept of the group as well as the treatment, it can reduce the unassigned variation in the experiment, making it more likely that significant results can emerge.
   For instance, a treatment could have an effect, but only in the larger cuttings.

But I thought everything had to be randomised!

Not everything. It is the individual cuttings within each group that need to be randomly allocated to treatments. Grading into groups is meant to be a conscious selection of unavoidable differences, just like choosing where the positions for the blocks should be in your experiment.

What about the propagating conditions?

1. Try to get the shading as uniform as possible (A 33), and extend it at least 3 m further than the propagation beds in all directions. Alternatively, use vertical palm fronds or hanging ‘curtains’ of shadecloth all around the bed, to avoid penetration of bright sunlight in the early morning and late afternoon;
2. Choose those beds (or parts of beds) which are most similar;
3. Where space permits, avoid using the edges and ends of beds;
4. Make up fresh rooting medium, and use it for the whole experiment;
5. Wash the polythene sheeting before setting up the experiment, and wipe it clean as needed.

Example of a simplified layout for rooting experiments

BLOCK I

BLOCK II

↓ continue with different randomisation for other Blocks

Can I improve the uniformity of auxin treatment?

Yes, the easiest way is to add one drop (about 50 microlitres) of an alcoholic auxin solution to the re-cut base of each cutting, using a micro-pipette. If you are testing auxin type or amount (A 40), make up solutions at different concentrations, so that you still add one drop to each cutting.
(Note: Alcohol evaporating from the stock solutions will make them more concentrated.)

Do research cuttings need extra day-to-day attention?

Yes. Unrooted leafy cuttings need to be kept in very humid conditions at all times, as they have no roots to take up water. This is especially vital in experiments, because variation in water stress can greatly confuse the results. Uniformity can be helped by the following hints:

1. spray evenly with fine drops of water; avoid over-watering (A 34);
2. spray early and late every day, not missing week-ends or holidays and especially during assessments and checks (A 50);
3. make regular checks on the condition and health of the cuttings, including removal of dead leaves (any dead cuttings removed should be noted in the experimental file);
4. maintain the shading in good condition;
5. use a small, flat piece of wood to lift cuttings when they may have rooted; don't pull them out of the medium.

What layout should I use for the experiment?

1. A most important point is to have plenty of replicates in each treatment (40 is an absolute minimum), or real differences won't show up.
2. For simple, ‘look-see’ trials, it may be acceptable to randomise rows of cuttings all of the same type or clone, or receiving the same treatment.
3. For trials of propagation conditions (e.g. shading, rooting media), a good method is to use a single, known clone throughout a series of experiments.
4. For larger experiments comparing clones, the effects of different types or origins of cuttings, or auxin application, etc, it is usually best to use a randomised block design, perhaps with each cutting individually labelled.

How about labels?

Before taking the shoots, write these clearly and firmly with a good HB pencil, not a pen. (Even the waterproof types can become indistinct in tropical conditions.) Labels will be needed for rows or for individual cuttings: abbreviate and condense the writing, but include all the vital information:

1. the clone number;
2. the treatment number;
3. the type of cutting (if this is a variable);
4. a letter showing the group into which the cutting has been graded;
5. the block number, species and date of setting can usually be shown on a (separate type of) label;
6. any other relevant information or warning notice.

What about records and assessments?

1. Records:
   1. Without full notes on the origin of the cuttings and the dates and details of the treatments and propagation conditions used (A 64, A 66 – 68), much of the value of your experiment will be lost.
      (Note:- Draw a map showing the layout of the cuttings in the propogation bed, and keep several copies safe in the office.)
   2. Measure the propagation conditions carefully (A 30, A 68), and find out how much they vary:
      1. from place to place;
      2. at different times of day.
2. Assessments:
   1. Record any changes in appearance of the cuttings, with the date.
   2. Carefully lift the cuttings with a small, flat piece of wood every 1 – 2 weeks, and record whether each is rooted, unrooted or dead; and the number of roots (A 65). (Do not let them dry up!)
      Pot up well-rooted cuttings, and replace the others in the bed.

What else is important?

A personal input into your experiment - plus the ability to look for explanations for the results other than those you were testing for.