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Trials of Long-stem Tube Stock at Katandra Reserve, Gosford NSW

The 'long-stem' method of planting for restoration of riparian habitats is now well established - an article on the method by the developer of the method, Bill Hicks, appeared in the March 2003 issue of Australian Plants online.

This is a progress report on the trials being carried out with the Australian Plants Society - Central Coast Group's Bushcare Group, Gosford City Council Bushcare Officer Geoff Hakewell and Bill Hicks.

Following an address given by Bill Hicks to our group meeting on the success of the 'Long-stem Native Tube Stock' that he developed for riparian work, the group discussed with him the possibility of using his methods with rainforest species for planting at our bushcare site in Katandra Reserve. The focus of this trial was to find out if rainforest species would survive and thrive if they were planted deeply in the same way as those used in the long-stem trials for the waterway restoration.

The stock for this trial was not grown to Bill's method. They were our normal plants grown from seedlings found around Seymour Pond and the gully rainforest area of the reserve and seedlings propagated from seeds gathered in that rainforest area and grown on. The plants were fed regularly and kept until each plant was of 'long-stem' size (approx. one (1) metre.)

Long-stem planting technique

Planting was carried out on 28th July 2002 during one of the Bushcare group's regular workdays. Equipment required on the day included hand tools for planting stock and construction plant protection, as well as a petrol driven, hand-held post hole auger.

Stock was installed using the following steps:
  1. Pre-water the stock while stilt in the pot.
  2. Marking out a suitable position for each plant on the ground.
  3. Removing dense ground cover from the planting locations where required.
  4. Digging a hole up to 80 cm deep and 20 cm wide using the petrol driven auger.
  5. Pouring approximately 5 L of water into each hole and allowing the water to percolate into the soil.
  6. Removing the pot and placing the plant in the hole to a depth sufficient to cover the stem of the plant, leaving not less than 90 mm of the stem and foliage above the ground.
  7. Back-filling the hole and applying 5 L of water to each plant.
  8. Constructing and installing a wire mesh plant protector secured to a frame of hardwood stakes (the guard protects plants from browsing wallabies).
  9. Inscribe and attach an identification tag to each plant protector.

The most significant difference between the methods of installing the stock for this trial, compared with other riparian trials, is the exclusive use of a petrol driver auger rather than a water lancing jet as described by Bill. This was due to the fact that our site is not situated near a suitable water source.

Monitoring planted stock

Two distinct monitoring processes were used in this trial. These were, firstly, to monitor the visible health of each plant over a four-month period - and, secondly, to determine if a plant does or does not develop adventitious roots in the buried portion of the stem above the original root ball.

Above-ground inspection

Following installation, all planted stock was monitored in July and early November 2002. Each plant was assessed to determine, firstly, if it was alive and secondly, if it showed signs of stress or ill health.

Stress or ill health was determined by criteria visible to the assessor without removing the plant from the ground. Criteria used to describe the plant as being in ill health or under stress included:
  1. Apparently healthy.
  2. Reduced turgidity in leaves (wilting).
  3. Loss of leaves with visible emerging buds, shoots or leaves to replace them.
  4. Loss of leaves and no visible emerging buds, shoots or leaves to replace them.
  5. Dead portions of woody stem.
  6. Death of the entire plant.

Plants that were damaged by insects were noted and recorded. While pest damage may lead to the death of a plant, the intention of this study was to record the response of the plants to long-stemmed planting rather than their susceptibility to pest attack.

Below-ground inspection

In late October 2002, a sample of each plant species was removed from the soil for examination. It was at this point that data relating to the initiation of adventitious root growth was collected.

In addition to the final above-ground inspection described previously, each specimen was inspected and assessed for the:
  1. Presence of adventitious root growth above the planted root ball.
  2. Absence of adventitious root growth above the planted root ball.
  3. Blemished covering of external tissue on the buried stem, with or without visible pest and disease.
The intention of this inspection was to determine if a plant species had developed adventitious roots, as well as looking for deterioration of the bark layer which may lead to health problems for the plant at a later point in time. Evidence of disease in the bark included:
  • Missing or decaying bark,
  • Pest attack resulting in loss of bark,
  • Soft or watery appearance of bark compared with other portions of the stem, and/or
  • Visible disfigurement due to a pest or disease.

Above and below-ground inspection of trial plants in Katandra Reserve
Plant NameAbove ground inspections per speciesDeadBelow ground inspections per speciesDeveloped roots above original root ball?
Acmena smithii8 54 
Alphitonia excelsa322 2
Ceratopetalum apetalum41312
Cryptocarya glaucescens4 321
Ficus coronata5 2 2
Ficus obliqua3 211
Glochidion ferdinandi7 761
Gmelina leichhardtii5 431
Neolitsea dealbata1 11 
Podocarpus elatus5 3 3
Schizomeria ovata4 22 
Sloanea australis1 1 1
Synoum glandulosum2 2 2
Tasmannia insipida6 312
Trema aspera91642
Total Plants674462521

Within this trial, Glochidion ferdinandi appears to be the most suitable species for long-stem planting. With one of the largest cohort populations and below-ground inspections for every member of the cohort, these plants show the strongest and most reliable evidence of lateral, sub-surface adventitious root growth. In addition, every member of this population survived and increased in height in spite of the dry climatic conditions and persistent insect attack.

Species such as Trema aspera, Acmena smithii and Schizomeria ovata provide some encouraging data. There were limitations within this trial to these and other species however, which may have prevented these species proving to be as, or more suitable than Glochidion ferdinandi. These limitations are discussed below.

One observation that can be made following this trial using long-stem planting method with temperate rainforest plant species is that it did not result in the death of an entire cohort of samples. This indicates that it is a useful tool in the short-term establishment of these plants, and is worthy of additional testing in order to ascertain the medium to long-term impacts of this system on this range of rainforest plants.

A factor that is unclear at this point in time is; if there will be any adventitious root growth in the future on plants currently assessed as not exhibiting this additional growth. In some cohorts, a longer trial period would lend a greater certainty to results regarding their tendency to root in this way, or even to improve their ranking, thereby indicating a strong tendency to root along the stem.

Discussions between the Australian Plants Society and Council Bushcare Officer debated several of the reasons for the survival rate of the plants. These discussions included the insulating properties of the soil in protecting and cooling the root ball. This characteristic of the system could have applications in very exposed or coastal locations. In these circumstances, revegetation project managers may benefit from identifying plant species that could have their roots deep in cooler and wetter soil, thereby reducing the need for mulch or other root protecting materials on slopes or unstable areas such as sand dunes.

Another observation made during this trial was the low impact of dense ground-covering plant growth (grasses, groundcovers, weeds, native Rubus sp.) on the growth of planted stock in the immediate vicinity. One advantage of the long-stem system would appear to be the fact that prior to the development of adventitious roots, the planted stock is not in direct competition with more shallow rooted plants for water or nutrients. In some instances, retaining and using the protection provided by tall dense weed growth may not only save a land manager the cost of pre-planting weed control, but it may also prove to be a positive step towards the survival and vigour of planted stock in the short- to medium-term. These savings in weed control may offset any additional cost associated with hiring the specialised planting equipment.

This trial of the value of long-stem planting technique in the rehabilitation of coastal temperate rainforests in NSW has proven to be successful for one species (Glochidion ferdinandi) and highlighted the opportunities for future research into the topic.

It has also been established that the long-stem planting system developed for use in large-scale riparian revegetation projects is suitable for small-scale revegetation projects in temperate rainforests.

Bill Hicks has encouraged us to carry out our trials using rainforest species and believes that other species of Australian native plants would be suitable for 'long stem' planting for rehabilitation in other soil conditions and environments. He would be pleased to talk to other Groups who may be interested in conducting trials using other dry tissue species.

Trials are in progress to grow on seedlings in tubes using Bill's formula. These will be looked after by Gosford City Council's Nursery until ready for planting.

We are grateful to Bill for his most valuable support during this trial.

Australian Plant Society - Central Coast Group
Gosford City Council
Katandra Reserve Bushcare Group

From the newsletter of the Central Coast Group of the Australian Plants Society (NSW) - March 2003 (via "Native Plants for New South Wales" - July 2003).


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Australian Plants online - March 2004
Association of Societies for Growing Australian Plants