Planting at Hobart College

We spent a morning session preparing and planting out a front entrance garden bed at Hobart College. Plants selected were Tasmanian natives, a good choice for a public space that requires low maintenance and tolerance to drought conditions and other extremes of temperature.

Topsoil had been imported for the job. In purchasing and importing soil, it is important to know that the soil meets Australian standards, is of an appropriate pH and as much as practically possible, weed seed free. As soil is not a sustainable resource, where possible, an attempt to improve the structure of existing soil should be made first.


An edge was cut along the existing bitumen with a circular diamond saw. Eye protection, ear protection, gloves and steel cap boots are essential P.P.E.



The edge of a garden bed is always visually important and if done properly can help to lock mulch in and minimise the amount that spills over the edge. A square mouth shovel is used to clear the bitumen rubble to achieve the desired depth at the edge.

Various tools can be used to roughen what is underneath the bitumen to allow ease of removal such as a three pronged tine. The shovel is effective when its sharp edge is placed at an angle to the edge and scraped along as well. The shovel can then be held flat to the undersurface to assist with leveling.

The photo below shows how a uniform gentle slope can be made by checking the angle using the back of rake.

Shrubs are planted by first digging a hole twice as wide and deep as the pot in which the plant is bought. Any clods should be broken up so that the soil is fine and crumbly. Ideally the plant should be watered in the container shortly before planting. The root ball should not be tightly packed. In bad cases, roots should be gently teased out. The root ball should be placed into the hole and soil added so that the shrub's trunk depth in the soil is the same as it was in the pot. Gently firm down the soil and then thoroughly water in. A slight depression around the trunk can help direct water to where it is most needed. On the other hand, if drainage is an issue, the plant can be mounded up.

Ideally, mulching should be done prior to planting, especially when multiple plants are to be placed in a bed. Here, we lay down a coarse pebble mulch after planting which caused a few problems, including damaging plants by accidentally pouring the mulch layer over them.

A coarse pebble mulch is an effective means of reducing evaporation from the soil surface and looks quite neat and tidy in a public space. It has the added advantage of not spilling as easily over edges as bark mulches, which can be strewn around by blackbirds.

Alternative edgings include the use of metal strips which are popular with landscape architects. They are expensive and require careful measuring to ensure they form a neat, continuous line. Metal perhaps wasn't the best option in this case since most of the other edging on site was created from wooden materials.

Harvesting Dutch Cream Potatoes

Area worked in : Production Garden, 25th March 

Activity Tasks : We worked with some of the organic certificate students to harvest a crop of dutch cream potatoes. Potatoes can be left in the ground where conditions permit, but the longer they are left the greater the potential for damage from rot and slugs. Generally speaking, early to mid autumn is a good to time to harvest. We used a garden fork to loosen the soil, being careful not to prick any of the tubers, and then pulling the whole plant out. Potatoes from one plant were placed into a pile to note amount, size and absence of disease in that plant. The best plants were selected to be seed tubers for the next lot of planting. 

Potatoes are best stored in the dark to prevent them turning green and developing high levels of a solanine, (a toxic alkaloid). A double layered paper sack folded loosely at the neck or a hessian bag are ideal. Ideal temperatures for storing are 5 - 10 degrees celsius. 

In the photo below there is a potato on the right with a either a bacterial or fungal rot which only infected one or two potatoes in a particular plant, while the rest of the tubers looked fine. The potato on the left is I think just really big!

White Clover (trifolium repens), a prostrate perennial herb with a rhizomatous growth habit, had been planted in rows along the beds to discourage the spread of rope twitch (agropyron repens). 

OH&S issues/PPE used : usual protective clothing to avoid exposure to sun and allergens. 

Environmental Work Practises : Leafy growth was disposed by composting and diseased potatoes were to be composted in a separate pile. It is recommended to avoid replanting potatoes in the same area for at least 4-5 years to avoid disease infestation. 

References :  RHS guide to fruits and vegetables

Work Placement 1 - TAFE

Area worked in :  Car Park Side Border and Main Border

Activity Tasks : 

March 11th : In a small group we removed all Poa labillardierii and  Lomandra longifolia from the bed. We used mattocks to form a circumferential trench around the grass and then levered the grasses out of the ground. We set these aside for division, propagation and planting elsewhere. We then started weeding out the rope twitch, which is extensive in this bed due to its rhizomatous growth habit and the lack of any form of cultivation in this bed for some time. We discovered localised areas within this bed of very poor drainage and water logging. The soil dug up in these areas had a nasty smell indicating quite poor anaerobic conditions. In addition, all the native pelargonium was pulled out using a pitchfork. We had not previously located and isolated the irrigation system in this bed and I caused a puncture in the poly pipe which required repair the following day. 

March 12th : With assistance from Roy Baker, we repaired the puncture in the irrigation system. This was done by first digging a trench with a shovel and exposing the site. We cut the section of pipe with a hand saw and later Roy obtained replacement piping which we cut to size, filing the edges and attaching to the two ends with plastic couplings. This was a cheap and reasonably quick process. We then flushed the entire section of the irrigation system to remove internal debris and cleaned the filters on each sprinkler. 

March 17th : We continued the process of manually weeding out the rope twitch present with a pitch fork and exposing the irrigation system fully to prevent further damage to it. We then carried out some pH testing using battery operated metres. These metres were calibrated first with known neutral (pH 7.0) solution. A 20g sample of soil was then mixed thoroughly for

 about a minute with 100mL of distilled water, making sure no organic matter contaminated the soil sample.  The meter was placed in the solution, being careful to avoid placing the meter in the soil sediment. To measure the pH we tested a couple of different sites in the bed instead of doing a composite analysis (soil samples taken from many different points in the one site and mixed together). This was because the soil profile at various sites demonstrated it was not 

an homogenous area.  Results are seen in the photo below. 

In the main border there were mixed pH readings of 6.3 and 7.4 where the westringias and hakea had been growing respectively. In the carpark border, pH 6.6 in the clay loam and 6.3 in the sandy loam. In the car park side border, pH 7.3 where a sad acid-loving camelia was growing and 6.4 on the other end. 

Soil texture analysis in this bed showed areas of sandy loam to clay loam.  

March 18th and 19th :  Worked on the main border where turf had been removed for a new section of this border. This area had a hard clay based soil which required breaking up first with a square mouth shovel. Shallow root masses were removed with a garden fork and then a pick-ended mattock was used to break up the clay even further. This was quite a physical exercise and proved more efficient when we worked in sequence, one person following on from the other person in a given area. We then leveled the bed as best we could with a metal rake, using the bottom end to level and the toothed end to break up clods and rake up surface debris. The last job was to place compost which had been previously calculated by the cubic metre in piles one metre apart and then spread by metal rake over the bed to a thickness of about 100mm. 

OH&S issues :  Constant issues included presence of cars and general public accessing area. These were addressed by wearing high visibility vests, placing signs and fluorescent witches hats around the area. There were no underground electrical issues in this bed. Holes left behind following the removal of the grasses became an issue and had to be addressed by leveling these holes. Risks of exposure to sun, potential allergens and insects was managed by wearing the appropriate P.P.E. Unused tools were placed in a corner leaning on a wall cl

ose to but away from the work site to prevent injury. Risk assessment sheets were completed for each day. Examples in photos below : 

P.P.E. : full sleeve shirt, broad brimmed hat, glasses, steel cap boots, long trousers, fluorescent vests. 

Environmental Work Practises : Proper disposal of the rope twitch had to be thought about to limit its spread. We used separate bins for the rope twitch and transported this to a separate section of the compost area. Solarisation by exposure to full sun is a safe and environmentally sound method of disposal of rope twitch. We ensured that we cleaned all equipment that we used prior to returning them to prevent spread of the weed. 

Reflection : It's important to know the location and isolate any underground piping or cables in an area being cultivated. We could have asked for the plans for the irrigation system before we started digging up the area. We could consider using the herbicide fusilade (targets monocotyledons non-specifically) but this would make it difficult to grow other grasses in the bed. Working efficiently means knowing how to use a hand tool effectively, with the least amount of physical exertion and working in a co-ordinated fashion.