Target Pruning and Cutting off a branch

Trees recover most rapidly from large cuts if they are smooth and do not damage the branch collar. If the branch is large, remove the bulk of it first to minimize the weight of what will fall last. First, an undercut is made, sawing to about a quarter of the way into the branch from the underside. This partial cut stops the bark tearing down the trunk if the branch accidentally breaks. Second, cut squarely from the top of the branch about 5 cm beyond the undercut (further away from the trunk) until the branch falls away - the cut should be made to the same level as the undercut. The finishing cut can the be made by following the line of the branch collar from top to bottom . Generally, the line of the cut is approximately 90 degrees to the branch bark ridge.

(above) Note first cut is an undercut and second is a top cut a little distance from the first.

(above) the same area, third and final cut must be smooth. Cut just beyond the branch collar at an equal and opposite angle to that made by the bark ridge on the main stem.

Below is a photo of a cut to remove included bark :

This is a weak point of trees and shrubs. Bark is embedded between opposing branches, creating a structurally weak point. It is best to eliminate these branches as soon as they are noted. If not, as the tree enlarges in diameter and weight, the tree is likely to split at this weak point.

In cutting much larger branches that could potentially be problematic in terms of where it will fall, a wedge can first be made to determine the direction of the fall :

Ref : RHS pruning and training manual pg. 12, 22

Scarification trial

Many seeds such as acacias have very hard seed coats and require a physical method to allow water to enter the seed and break dormancy. Such a process is called scarification. This can sometimes be done with sandpaper, using nutcrackers or nicking with a knife depending on the type of seed. Soaking in hot (not boiling water) for up to 48 hours is another method. Seeds must be sewn directly after the soaking period and must not be allowed to dry otherwise they die.

This trial was to compare germination rates of Acacia verticillata and Dianella tasmanica when seeds had been scarified by soaking in hot water for 24 hours compared with seed that had been given no prior treatment.

10 seeds of treated and 10 seeds of non-treated A. verticillata were sewn in different punnets. The same was done for D. tasmanica. This occured on the 23rd April.

Photos of A. verticillata punnets taken on 19th May, about 4 weeks later, with top punnet containing treated seeds and bottom punnet non-treated :

After 6 weeks (non-scarified on left and scarified on right) :

Note the strike rate for scarified seed is 8 out of 10, whilst non-scarified is 2 out of 10.

This shows that germination rates are higher when Acacia verticillata has been scarified.

At 4 and 6 weeks no Dianella tasmanica had germinated, as is expected with the time it normally takes to germinate.

reference : RHS propagating plants pg 53-4

leaf bud cuttings

Most Camellias can be propagated from leaf bud cuttings of current season's growth that has begun to firm (ie. semi-ripe cuttings, where the base of the cutting is quite hard and the tip of the cutting is still actively growing and thus still quite soft). These cuttings include the leaf and axillary bud or node. This allows for many cuttings to be taken from the same stem. Cuttings are made the same size to allow ease of handling by ensuring most cuttings take root at roughly the same time. These are placed into the prop. mix after each cutting has been dabbed in rooting hormone gel, leaving the bud on the surface of the mix. Flower buds are pinched out. With bottom heat, rooting usually takes 6-12 weeks. 

We also took some leaf bud cuttings from a potted Ficus elastica cultivar. Using secateurs, a cut was made straight across a stem just above a node - a rule of thumb is about the distance of the width of the stem itself - and about 2.5cm below the same node. Keeping the waxy side of the leaf outermost, the leaf was rolled to form a cylinder, secured with a rubber band and placed into the prop. mix after a dab in semi-hardwood rooting hormone gel. The lead node should sit on the surface of the mix. The cutting can be supported with a small cane through the rolled leaf as shown above. This is kept in the misting house under humid conditons until rooted. 

Larger leaf Camellia varieties can be handled in a similar manner as shown below : 

Ref : RHS propagating plants, pg. 95, 120

Root Cuttings

A limited range of plants, particularly ones that naturally produce suckers from the roots can be propagated from root cuttings. In this activity, I propagated Wisteria sinensis, whilst others propagated Acanthus mollis, using this technique.

Appropriate cuttings were located by digging carefully with a trowel around the base of the selected Wisteria vine, ensuring no damage was done to the larger root system. Root cuttings were of pencil-thickness, although thinner root cuttings are also just as successful. The thinner the cutting the longer they should be. Cuttings are best done in autumn or winter when the plant is dormant. The cuttings are then lightly washed in water to remove soil.

Each root section is cut into approx. 5cm sections. To make sure the cuttings are inserted the right way up, the base is cut horizontally and the top at and angle.

The cutting is then dabbed in semi-hardwood rooting hormone and then inserted into the propagation mix.

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The cuttings are then watered thoroughly and placed into the misting house on top of a capillary sand bed with bottom heat.

Ref : RHS Propagating Plants, pg. 23-4, 158

Below is a photo of Acanthus mollis root cuttings prepared on 19th May and photographed on the heating and misting beds almost a month later on 17th June :

Cold moist stratification

Some tree seeds have a physiological dormancy which can be broken by certain levels of cold or heat. Such seeds need to be treated by stratification.

In this exercise, we used seeds from Betula pendula, Acer buegeranum, Zelkova serrata - all deciduous trees native to the Northern hemisphere. We chill seeds in a refrigerator at temperature between 0 - 5 degrees celsius, to mimic the passing of winter and to gain a more even germination. Seeds need to be kept moist and so are sealed in plastic bags before being placed in the refrigerator.

Betula pendula catkins were harvested from the TAFE garden.

Samaras from Acer and Zelkova spp. were collected from the Botanic Gardens.

The seed-raising mix used consisted of equal parts of pasteurised sand, cocopeat, perlite, combined with trichodry and mini-osmocote.

A low punnet was filled with this mix and tamped down gently but firmly.

Betula seeds were scattered as a thin layer across the mix and then covered lightly with the same mix.

Zelkova and Acer seeds were placed gently by hand in the mix and again covered lightly.

These were then watered and placed in plastic bags and refrigerated as previously mentioned.

Betula pendula stratification period was from 22/4/09 - 15/5/09 (25 days)

Zelkova serrata and Acer buergeranum from 22/4/09 - 14/6/09 (55 days)

After each stratification period, punnets were removed from fridge and placed on heating and misting beds.

Betula pendula seedlings all had excellent germination rates and were pricked out on 30/6/09 :

Ref :RHS propagating plants, pg. 54

Disease 6 - Leaf twist virus in grapefruit

Citrus trees are best grown in warm to hot climates, with mild winters. Some varieties of citrus, however, can be successfully grown in colder climates, including this grapefruit variety, "Wheeney." 

The above photo shows a viral infection, with symptoms of yellow mottling on leaves and puckering, although this could be also due to a combination of frost and wind damage. Viral infections in citrus are untreatable and like with all other viral infections, prevention by buying specimens propagated from virus-tested and/or more resistant material is the key. 

Ref : Judy McMaugh, pg. 73-4

Disease 5 - Daphne Virus

Daphnes grow best in cool areas and need soils rich in organic matter and slightly acidic. They prefer semi-shade and a cool, moist root run, so mulching is important. Daphne odora, the most common species, suffers from a number of viruses. These viruses are untreatable, but more resistant varieties have been released, termed "High health" plants. 

Symptoms of viral illness are shown in the specimens above, found in the Royal Botanic Gardens. They can include yellow blotches, irregular streaks, dead flecks, twisting or puckering. Flowers are often small, distorted and green. The whole plant may be stunted. 

Ref : Judy McMaugh, pg. 107

Pest 8 - Borers in Cercidiphyllum

Borers are a major problem for ornamental trees. There are a wide variety of borers. Once infested, there is little that can be done to control the insects in the wood. Keeping trees as healthy as possible is the best way to prevent borer damage. Trees that are old, drought stressed, or over watered, or otherwise unthrifty are most likely to be successfully attacked by borers. Borers always attack at joins of branches. The activity of borers encourages fungal disease, general weakening and eventual destruction of that part of the tree. 

Most of the borers encountered are beetles but some are caterpillars of clearwinged or other moths and others are primitive wasps. Pictured below is the frass (collection of excreta, thread, dead material), which acts as a protective, cushioning covering over the hole of the borer insect. The plant affected is a Cercidiphyllum japonicum (Katsura Tree), a deciduous tree found in the Japanese garden area of the Royal Botanic Gardens. 

An attempt can be made to treat borers by applying methylated spirits via a straw down the hole and sealing the entrance with putty. 

On a neighbouring Katsura tree, there is also a preying mantis egg case or ootheca. 

ref : University of Idaho website, pers. comm. Marcus Ragus

Disorder 3 - Frost damage to capsicum

Frost and, more specifically, alternate freezing and thawing can destroy plant cell walls, often killing tender plants, but hardier species can be affected as well. Bedding plants and tender vegetables, such as potatoes and tomatoes, show a range of symptoms in cold weather: leaf darkening or yellowing, leaf curling, scorch, tissue destruction and even plant death. Here is an example of damage to foliage of a variety of capsicum following an early morning frost in the production gardens at TAFE. Preventing frost damage involves choosing planting positions carefully to avoid 'frost pockets' (where cold air settles at the bottom of a slope), or a position in early morning sun. Other tips to prevent frost damage : 

- don't apply nitrogen-rich fertilisers late in the season as they stimulate soft, sappy growth which is especially vulnerable to cold damage

- Cover plants with a double layer of horticultural fleece or in a frame when frosts are forecast.

- Grow frost sensitive plants near walls that may radiate some heat at night. 

Ref: Judy McMaugh, pg. 20, Royal Horticultural Society Website

Disorder 2 - Phosphorus deficiency in brassica seedlings

Phosphorus is one of three major elements required by plants for healthy growth, flowering and fruiting. It remains relatively immobile in soil and resists leaching from heavy rain or watering. Australian soils are often, however, deficient in phosphorus. 

In soils with low pH, phosphorus is less soluble and therefore less available to plants. This limits growth. Cold weather can cause a temporary deficiency. Symptoms include poor growth and leaves that turn blue-green but not yellow (as in nitrogen deficiency).  Oldest leaves are affected first. Here, in the brassica seedlings at TAFE, the leaves are a red-purple colour. 

This phosphorus deficiency can be corrected by planting out these seedlings in a soil with plenty of organic matter. Decomposted animal manure, particularly poultry droppings is rich in phosphorus. 

ref: Wikipedia and Gardening Australia, Judy McMaugh pg.10

Pest 8 - Red-headed cock chafer

These are the larvae of scarab or cock-chafer beetles. They were removed from the soil they were dug out of and placed on asphalt for the sake of this photo. 

McMaugh refers to the larvae as white curl grubs. They are whitish with an orange-brown distinct head and long jointed legs. They usually rest curled into a semi-circle. Most larvae feed on plant roots, but some feed around the base of low-growing plants. Strawberry plants may have their roots eaten right to the crown. They can be a serious problem in potted plants. A wide range of plants are attacked. 

Control is achieved naturally through birds, fungal and viral diseases, predaceous insects like ground beetles. In potted ornamentals and in turf they can be controlled by fenamiphos granules (Lawn Beetle Killer) applied as directed. 

Beetles mate in summer and eggs are laid in soil usually where there is no thick grass cover. beetles form a tunnel to the surface and emerge at night to feed on leaves which they chew off at ground level. Feeding continues through summer, autumn and winter. In late spring, the larvae pupate and the next generation of adults emerge in summer. 

Ref : Judy McMaugh, pg. 139, 209

Pest 7 - Galls caused by insects on Allocasuarina

Various species of insects, especially coccoids (Hemiptera) form distinctive galls on Casuarinaceae; some of these may be mistaken for fruiting cones but they are actually modified vegetative branchlets. Coccid galls also affect eucalyptus species. They are a group of sap-sucking insects whose saliva stimulates plant cells to grow in such a way as to form a gall that looks somewhat like the fruit of the allocasuarina. Control is usually unnecessary, but removing young galls from the plant may reduce future infestations. 

Above is a photo of a psyllid gall on the same allocasuarina species in the Domain near the Botanic gardens.

Ref : Judy McMaugh, pg 148, Australian National Botanic gardens website.

Pest 6 - Echium leaf miner

There are a number of different insects whose larvae feed inside the leaves. These are referred to as "leafminers." Adults may be beetles, wasps, sawflies, moths or flies.

In the case of the Echium leaf miner, the pest is a caterpillar feeds underneath a blister-like, brown papery patch in between the veins on the undersurface of the leaf. The adult is a moth pictured below :  Photo: courtesy of Ken Bond, Dept of Zoology, Ecology & Plant Science,

University College, National University of Ireland, Cork, Ireland)

Echium leaf miner was officially introduced in the mid to late 1980s in South Australia to control the noxious weed Echium plantigeneum or Patterson's Curse. In the photos above it is affecting leaves of an ornamental species, Echium pininana, found in the Asian Woodlands section of the Royal Tasmanian Botanic Gardens. 

Ref :  Judy McMaugh pg. 179, University of Technology Sydney Website, pers. comm. Marcus Ragus

Bacterial Leaf Spot on Fuchsia

Bacterial Leaf Spot affects a range of hosts and is caused by a variety of bacterial organisms. Hosts include cucurbits, lilac, lettuce and pelargoniums. These photos show the ill-defined, black spots with irregular edges which can coalesce. Copper-based sprays may help. 

reference : McMaugh, pg. 224-225