Oxalis Eradication

It is the Winter Solstice in the Southern Hemisphere and the yellow-flowered weed Oxalis pes-caprae is beginning to flower in our local parks and reserves. You will want to stop this weed in its tracks if you have it in your garden or  native wildlife reserve. 
 Oxalis is not an easy plant to suppress because, as well as spreading by seed, it produces tiny underground bulbs that break off when you pull out the plant.

 Early to mid-winter is an ideal time to tackle Oxalis. One person can do this alone in a domestic garden but in a park or reserve it is better to divide up the area into bight-sized pieces and share the load between a group of volunteers. I am experimenting with the following method of weeding a small area near the bridge in Newell's Paddock Urban Park. If successful, this method might work for our Friends of N. P. and other volunteer groups:




 Seven Step Glysophate-free Method of Controlling Oxalis
1. Concentrate on thoroughly eradicating a small area to begin with. Choose a site that is easy to access and that you will enjoy intensively weeding. If you have a large area of Oxalis it will be impossible to clear the entire infestation in one season. Choose a small area (no more than 2 sq. meters per person) to intensively weed by hand but don't ignore the remaining infested areas. Hand-weeding Oxalis will take several years and requires commitment. I weed my special site for ten or fifteen minutes once or twice a week, combining it with dog walking. I always keep my chosen hand-tools- a two pronged weeder and an old bread knife- plus an extra plastic bag in my dog-walking kit.

2. Avoid disturbing the soil. Remove Oxalis plants as early in their growth stage as possible by digging out the plants using a small hand-tool. If the Oxalis is coming up through another plant, try easing it out using a screw driver or knife so as not to disturb the roots of the plant you want to keep.
Alternative safe chemical method: In a small spray bottle, mix 4 teaspoons of Baking Soda to a litre of warm water, add some washing up detergent and shake. Squirt a dose of this mixture directly onto the leaves of individual Oxalis plants on a dry, sunny day. I haven't tried this yet but a combination of both methods might be a good approach. Be prepared to repeat this process throughout the winter growing season. Repeat the process diligently next winter as many Oxalis bulbs will remain in the ground. Eventually, without leaves, they will run out of energy.

3. Don't infest another area*. Dispose of dug-up Oxalis plants by placing them in a plastic bag, sealing it and leaving it in a sunny place to sol-anise (cook). I wait until I have filled a plastic shopping bag with weeds before I place it on the roof of the shed at home for a couple of weeks before putting the bag in our landfill garbage bin.

4. Nature abhors a vacuum. Plant to replace the weeds in the area you have intensely weeded. Aim to smother or out-compete weeds with local ground-covers. Seek out suppliers of local indigenous ground covers. Salt bushes are the first line of defense, then Poa, Dianella and Lomandra species. In a bush-land garden or wildlife reserve, observe to see if indigenous plants spontaneously appear.

5. Nip it in the bud. It is important to remove all the buds and flowers of Oxalis growing within a radius of at least 5 meters from your intensely weeded site. Using garden shears or a bread knife, cut off the flowers and seal them in a plastic bag*. As you finish completely clearing one small area you can begin to expand into the surrounding areas. The seed pods of Oxalis burst, releasing hundreds of tiny seeds that can be dispersed by the wind, enabling thousands of Oxalis plants to reappear next year, including in the area you have already spent hours intensively weeding. 

6. Mulch the surrounding area. Aim for a layer about 750 mm deep. Each Oxalis plant has a fleshy tap root to store energy to tide it over to the next season. Oxalis will break through a thin mulch. Oxalis seeds can germinate in thick mulch but at least seedlings will be easier to pull out!
 
7.  Be prepared to persist for at least three years. Expand your intensely-weeded zone next year and in the years following. Revisit and deal with any Oxalis outbreaks in your original intensively weeded area.

Queensland fruit Fly in Apricots

Unfortunately all the fruit on our apricot tree is affected by fruit fly. It is impossible to see until the fruit is cut open to reveal the small white larvae. Even firm, semi-ripe fruit contained larvae. Pat, Jo and I sprang into action to remove all the fruit both on and under the tree. The fruit were sealed inside black plastic bags, tied securely and have been left in the sun for at least a week to be cooked by the sun. Alternatively we could have cooked all the fruit in a microwave oven or frozen it. Dispose of the sealed plastic bag in the garbage bin, not the compost bin.

Reporting Fruit Fly Outbreaks:  I rang the relevant Government Department but was advised by a very nice person  that the only area of Victoria currently fruit fly free is around Mildura. South Australia is the only fruit-fly free state on the Australian mainland. Reporting fruit fly outbreaks elsewhere has been suspended. She directed me to http://agriculture.vic.gov.au/agriculture/pests-diseases-and-weeds/pest-insects-and-mites/queensland-fruit-fly/fruit-fly-action-plan. It was worth looking up; very clear, comprehensive information.

Fruit fly Prevention: We will not be using chemical prevention methods in our Permaculture fruit forest. We have removed all the fruit, cleaned up under the tree, disposed of the affected fruit and Jo pruned the tree today. If we can get a grant to buy nets at $60 each, we will net all our fruit trees next year. We are monitoring the apple and nectarine trees at the moment. Fruit fly do not attack olive trees. They attack almost all other fruit including tomatoes.

Stewed apricots salvaged from damaged fruit

Salvaging some Apricots: I took home about 1.5 k of under-ripe apricots and after cutting out the affected parts of the fruit I was able to save about 750 gm of good apricot flesh which I stewed with 2 T of sugar and half a cup of water. The result was very pleasing- sweet, more flavoursome than the unripe fruit and a good colour. After I prepared the fruit I disposed of the fruit fly affected waste  in my Bokashi compost system. This is not the recommended method of disposal but I feel it is safe because it is a sealed system which works by fermentation; I doubt if a larvae could survive the process.

Harvesting Apricots

 Apricots are nearly ready to be harvested in the Farnham Street food forest at the start of January. The fruit needs to be slightly giving to the touch and a true apricot-colour before it is perfect to pick. Unfortunately that is how birds and flying foxes (Pteropus poliocephalus) like their apricots too. Already birds are beginning to peck at the unripe fruit. Our tree is part of a complex mosaic of fruit trees and under-story plants so it would not be possible to net. The only solution is to pick apricots semi-ripe or remain constantly vigilant to beat the early bird to the choicest fruit. The fruit on the north side of the tree ripens ahead of the fruit on the shady south side.

Early January: fruit almost ripe.

October: green developing fruit

Unripe apricots harvested with just a blush of colour are best sliced and stewed or microwaved for just a minute and added to muesli or ice cream. Apricots are difficult to store out of the fridge; even a slight blemish or bird peck on the skin will quickly turn into a rotten brown spot. In a fruit fly prone area all fruit needs to be picked and stewed before they are fully ripened unless preventative measures such as fruit fly exclusion net has been erected over the tree. Areas experiencing spring frosts can only grow mid and late season apricot varieties like Trevatt and Morepark but if spring frosts do not occur in your area choose apricot varieties that fruit early such as Glengarry, Caselin and Divinity in order to harvest apricots in spring and early summer before fruit fly become active. In Melbourne you can be pretty certain there will be no spring frosts.

Cold winters are required for maximum fruit set but lack of fruit may be because the tree is young or pruning was too severe. If too much of the previous season's growth is pruned, there will be little fruit the following year. Leave some one-year old and and some two-year old shoots. Pruning is best done in summer after fruiting to avoid Gumosis disease. It is important to keep the water up after harvest to encourage formation of next year's flower buds. Feed the tree with compost or worm castings but not high nitrogenous fertilisers. Be very careful not to dig around an apricot tree or you will have suckers coming up from damaged surface roots.