Casuarina (Australian pine) Status in Florida

Windbreaks for Citrus

Literature | Research Publications | Casuarina Propagation

 

Important Note:  There are three species of the non-native Australian pine (Casuarina spp.) in Florida.  Their spread in some areas of the state has resulted in each species being classified by the Florida Department of Environmental Protection as invasive and subject to removal according to the following: "The Florida Department of Environmental Protection (FDEP) lists all "Casuarina spp." as Class I Prohibited Aquatic Plants, which prohibits them from possession, collection, transportation, cultivation, and importation without a permit from the Department (62C-52.001 FAC).  Casuarina equisetifolia and C. glauca are listed on the Florida Department of Agriculture and Consumer Services' (FDACS) Florida Noxious Weed List (5B-57.004 FAC). It is unlawful to introduce, multiply, possess, move, or release Florida Noxious Weeds within the state without first obtaining a permit from the DACS." 

In 2008, legislation was signed into law permitting restricted propagation of Casuarina cunninghamiana.  The law allows only vegetative propagation of Florida sources of male Casuarina cunninghamiana plants for use as windbreaks in citrus groves in only Martin, St. Lucie and Indian River Counties.   The Florida Department of Agriculture and Consumer Services, Division of Plant Industry, is the rule-making and regulatory authority.  Click here for legislation details.

Vegetative Propagation

Casuarina cunninghamiana is a dioecious plant which means that one plant produces female flowers and a separate plant produces male flowers.  Remember, only male plants can be propagated by vegetative methods. 

If you intend to commercially propagate this plant, it is highly recommend that you review previous studies on rooting cuttings to best understand the various treatments attempted by others.  Also, our efforts at the CREC to root cuttings has met with limited success.  The following are descriptions of various publications with the most practical information, and a summary of propagation attempts and results at the CREC.  For questions and further details, please contact Dr. Bill Castle: 863.956.1151, bcastle@ufl.edu.

When propagating Casuarina cunninghamiana, note also that the plant normally forms N-fixing nodules with a bacterial species in the genius Frankia.  Whether inoculation is necessary for the plant to grow is an unsettled matter.  Based on a very limited sampling, nodules are not easily found among surface roots for Casuarina trees growing in Florida.  Propagators wishing to attempt inoculation may try growing rooted cuttings in soil collected from under mature trees.

Propagation Literature 

Chemical concentrations.  Some concentrations in the literature are reported in milliMolar (mM) units, others are reported in parts per million (ppm).  The relationship between mM and ppm is as follows: look up the molecular weight (MW) of the substance.  A 1 mM solution is the MW (in milligrams) in one liter of water.  Example:  The MW of NAA is 186.21 g.  A 1 mM solution is 186.21 mg in 1 L of water.  One ppm is 1 mg/L, thus, 200 mg  NAA/L = 200 ppm NAA.  Therefore, a 1 mM solution of NAA is 186 ppm.  The MW of IBA is 203.2 g.  A 1mM solution of IBA is 203.2 mg/L.

Propagation of cuttings by water culture in China

Casaurina Propagation

The procedure used in China is independent of plant gender.  In Florida, only male plants can be used.  The Chinese procedure involves establishing a plantation of young trees that are cut near the soil-line to induce young shoots.  Those shoots are harvested when they are 3 months of age or younger and  3-4 inches long.  About 20 or 30 cuttings are placed in an ordinary opaque plastic 12 oz. cup with about 1 inch of rooting hormone solution (50 -100 ppm NAA or IBA).  The cuttings soak for 24 hours.  [Note: the soaking solution is NOT made by taking a commercial rooting compound and dissolving it in water.  The hormone solution used by the Chinese is made from the pure compound.]   The cuttings are removed and placed in another cup with only tap water.  The cups are placed outdoors in a shady place.  The water is replaced daily.  Rooting apparently occurs within 4- 6 weeks.  The contact person in China is Dr. Zhong Chonglu: zhongchl@pub.guangzhou.gd.cnzclritf@21cn.com

Micropropagation of Casuarina

This reference is mostly a review about rooting cuttings and producing plants by tissue culture.

Macropropagation of Casuarina cunninghamiana Miq. via Mistless Polytunnel (Hydropit)

Cuttings, 6 inches long, were treated with 1000 to 3000 ppm IBA and rooting increased from 13% to 40%, respectively.  Cuttings from trees of unstated age were placed in polybags with 1:1, soil:sand, and placed in a trench with plastic sheeting on the bottom and a layer of sand.  The trench was covered with “polysheet” and the sand base watered as needed (to maintain high humidity in the pit).

The Propagation of Casuarina Species from Rooted Stem Cuttings

This reference reports one of the most comprehensive and successful studies.  Three types of cuttings were used:  hardwood, softwood, juvenile (see report for definitions).  Commercial rooting compounds were used for dipping the cuttings which were then placed in sand.   Some cuttings were rooted in water culture or an aerated hydroponic system.  The best results (60%) were achieved with mature softwood cuttings treated for 3 hrs with 50 ppm IBA.

A Simple and Efficient Method for Clonal Propagation of Casuarina sumatrana

As in the preceding study, mature softwood cuttings from side branches of 10-12-year old trees were rooted after a 5-second dip in a broad range of NAA and IBA solutions: 200 – 2000 ppm (1-10mM).  The cuttings were rooted in “plastic troughs” and high humidity was maintained.  The propagation chamber is described.  Rooting percentages ranged from 0 to 70%.  The rooting response with this species was much greater with NAA than IBA.

Propagation Experience

Contained in the literature are many helpful hints on Casuarina propagation.  Some of the reports are incomplete in that important information about the type of the cutting, the age of the trees from which they were harvested, and the rooting chamber and propagation conditions are missing. 

At the CREC, we have attempted to root cuttings using some of the procedures described in the literature, and other techniques.  What follows are what we consider to be important from our experience in combination with what is reported in the literature.

Type of cutting.  There are three types: a hardwood cutting which literally has a hard stem with brown color and is at least 3 months old; semihardwood which in this case would not be easily distinguished from the first type; and, softwood which is a shoot about 3 months or younger with a relatively soft green stem. 

Fig. 1.  A typical branch (left) of Casuarina showing the tip which is normally suitable for harvesting cuttings, and the lateral branches often noted in the literature as better sources of cuttings.  Illustrated above are cuttings taken from one lateral branch and identified as to type.  The softwood cutting (A) has a green stem that is literally softer to the touch than other places along the branch stem.  The hardwood cutting (C) has a well-rounded stem that is brown and hard to the touch.  The semi-hardwood cutting (B) is intermediate in those characteristics.

Fig. 1.  A typical branch (left) of Casuarina showing the tip which is normally suitable for harvesting cuttings, and the lateral branches often noted in the literature as better sources of cuttings.  Illustrated above are cuttings taken from one lateral branch and identified as to type.  The softwood cutting (A) has a green stem that is literally softer to the touch than other places along the branch stem.  The hardwood cutting (C) has a well-rounded stem that is brown and hard to the touch.  The semi-hardwood cutting (B) is intermediate in those characteristics. 

Such cuttings can be harvested from a mature tree or a juvenile tree, thus, any cuttings from a 1-3-year old tree (one that has not flowered) might be labeled using a combination of terms, i.e., it is possible to harvest a softwood or hardwood cutting from a juvenile or a mature tree.  IMPORTANT POINTS:

  • Softwood and juvenile cuttings may be the best, but our experiments so far do not suggest that one type of cutting is better than another.  For propagators, trials should be conducted with all types; also, having rooted cuttings of male trees growing on-site in containers as source trees may be advantageous.
  • The right type of shoots can be produced on any tree by cutting back small branches of ¼ to ½ inch diameter and waiting for new lateral shoots to appear.  The new shoots can be harvested when they are 3 months old or younger.  In the spring and summer, our experience is that shoots will appear with 2-3 weeks and grow rapidly enough to be the right length for harvesting within 3 months.
  • Most rooting successes reported are based on 4- to 8-inch cuttings harvested from lateral rather than terminal shoots.

Handling of cuttings.

  • Humidity appears to be very critical.  The cuttings must be kept moist at all stages.  Misting might be acceptable, but in many cases, the use of a propagation chamber in which the humidity is kept high all the time might be better.  
  • Stick the cuttings as quickly as possible and no longer than 24 hours after harvest.  Remove the needles from the bottom 1/3 of the stem.
  • When harvesting, clip off small branches that include the cuttings you will use rather than clipping the cuttings directly.  By following that step, water loss is probably reduced.  Place the branches in bags and keep them moist.
  • We have encountered fungal problems especially in water culture.  As a result, we dip the cuttings for 30 seconds in the field using commercial household bleach diluted 3:1 followed by a rinse in tap water.  Also, in water culture, a fungicide like Banrot® (0.5 oz/gal) is added to the water.
  • The basal end of the cutting is re-cut before hormone treatment usually at a 45° or steeper angle to promote uptake of the hormone.
  • To reduce water loss, we have experimented with a spray-on anti-transpirant, Wilt-Pruf®, applied before the cuttings are placed in the medium.  No clear benefit has been evident so far.
  • The spacing between cuttings in the propagation facility may be important especially to help preclude fungal problems.
  • How do you know if the cuttings are doing well?  Cuttings are a healthy green color when harvested.  If at any point they turn dull green, they will not survive.

Hormone treatments.  The common hormones are naphthalene acetic acid (NAA) and Indole-3-butyric acid (IBA).  Solutions of the individual compounds are used as dips or in combination.  Various commercial products employ these compounds as well, usually in powder form. 

  • Concentration.  In general, the range used has been from about 50 ppm to 3,000 ppm with limited consistency in results, thus, propagators are encouraged to try various concentrations.
  • Compound and application method.    A summary of reported trials and those we have conducted at the CREC is available here.  Powdered materials are applied by dipping, hormone solutions have been applied by a quick dip (5 seconds) or prolonged soaks that lasted from 30 minutes to 24 hours.  Long soaks (> 30 minutes) with IBA concentrations > 200 -500 ppm turned the base of the cutting stem black and diminished rooting success.

Response time.  Rooting seems to occur within 6 to 8 weeks.

How to Root Cuttings of Male Casuarina cunninghamiana Plants in Florida

To proceed with propagation, please note that you must be in compliance with the following:

    • A permit must be obtained from the Florida Department of Agriculture and Consumer Services, Division of Plant Industry.   For an application and guidance, contact your local DPI plant inspection office.
    • Only male plants of Casuarina cunninghamiana are permitted to be propagated by Florida Statue and they can only be used as a windbreak for citrus in Martin, Indian River and St. Lucie Counties by separate permit.
    • Source trees for cuttings are registered with the DPI and are the only legal source of cuttings. 
    • Harvesting cuttings must be witnessed by a DPI Plant Inspector.

    Propagation Protocol

    1. Read the publication “Field Guide to Identify the Common Casuarina (Australian Pine) Species in Florida” available @http://edis.ifas.ufl.edu/HS394.This document describes Casuarina species and provides valuable background information.
    2. Go the UF/CREC website @ http://www.crec.ifas.ufl.edu/extension/windbreaks/index.shtml for additional information about propagation and an illustration of the type of cutting that has proven so far to be the easiest to root.
    3. There are currently two approved private sources of mother plants certified for cuttings:
      1. Russakis site, Indrio Road, Fort Pierce
      2. Kenco Manufacturing, Ruskin
    4. To collect cuttings, there are two options:
      1. Take individual 4 to 6-inch main branch tip cuttings or side branch tip cuttings.
      2. Remove a whole branch, transport it to your facility and then remove the types of cuttings described above.
    5. Keeping the cuttings moist is ABSOLUTELY CRITICAL! If they dry, they will die. If the cuttings at any point during propagation turn color from the bright green they are when attached to the tree, to dull green, they are unlikely to survive.
    6. Use a peat-based rooting medium.
    7. Treat the cuttings with a hormone. Various experiments have not revealed a particularly superior compound or combination of compounds, but a commercial product with a Indole-3-butyric acid @ 00.3% concentration is presently recommended.
    8. Insert the cuttings about one inch.
    9. Provide mist in a cycle such as 5 seconds mist every 15 minutes.
    10. Scarification of the stem to be inserted into the rooting medium may be helpful.
    11. The rooted cuttings must be hardened off after rooting.

    Top