Posts Tagged ‘garden’

When is a weed not a weed?

In April 2014 on April 15, 2014 at 3:22 pm


A ScienceforLife.365 guest post by Dr Heather Bray* 

Heather: My garden needed a darn good weeding this morning. I spent a couple of hours on it, furiously pulling up or digging out the offenders, being careful not to disturb the plants I have nurtured since before the summer..

When it came to this little fellow however, I left him alone. I decided this one wasn’t a weed.

The best definition for a weed is the first one I learned in Year 7 Agriculture:

A weed is a plant in the wrong place.

We decide which plants are in the right place and which ones aren’t based on a whole range of factors; many of the reasons are based in science, but some are not. Some plants are dangerous and so we consider them weeds because they are toxic to humans or animals. Some weeds can affect nearby plants through competition for resources in the soils or by suppressing their growth through allelopathy. Some weeds are invasive and push out indigenous flora. Other weeds cause harm indirectly, and are considered a pest because their presence in association with other plants can reduce the purity, quality or price of an end product destined for market.

But some weeds are pretty, and so we choose to leave them where they are, or move them to another place and even help them to grow. Those of us who live in urban areas will be mostly familiar with this aesthetic idea of a weed as we arbitrarily decide whether a plant is in the right place to suit our own needs.

By some definitions, all the plants in my garden are weeds. The heartsease pictured above I spared quite simply because I like it. This particular one is an escapee, being self-sown from a plant in a pot.

I also have lots of arum lilies, the loveliest of all the weeds in my opinion. These remind me of the times I did practical work on dairy farms in NSW, where there were often clumps visible in the paddocks. All the ones I have now came from three lilies I brought from a previous garden, so I can see how they can ‘jump the fence’ and become a pest. There are also weedy tendencies in agapanthus, the species I used to re-establish the garden bed quickly (after the process of getting a new fence trashed what was previously growing).

I do feel a little guilty sometimes about both of these plant choices, but I’m planning on selling my house soon and needed something cheap, pretty and hard to kill. And they are everywhere in gardens around where I live. At least I haven’t planted lantana, a common Adelaide garden plant and ‘Weed of National Significance’ – I have vivid memories of seeing this species fill whole valleys of bushland in coastal NSW.

A weed is a wonderful example of something that is both a scientific concept and a social one. Ideas about what plants belong where can be constructed socially and culturally. There are others; for example ideas about food and naturalness are both influenced by factors other than science. It is important when we want to engage the community in discussions about scientific ideas that we don’t assume everyone will see things in the same way.

One person’s weed is another person’s flower, and so my little heartsease is safe … for now.

*You can find Heather on twitter as @heatherbray6


The dead tree bed

In November 2013 on November 4, 2013 at 10:49 am


A guest post by Tiki Swain*

My dead tree bed is a tricky space, an ongoing garden experiment.

The dead tree was once a citrus, but it didn’t survive the droughts Perth endured in the last few years. The old Italian grape vine sprawling over it however managed fine.

My initial idea was to remove the dead structure and make a mini-citrus orchard. But as I studied the garden system as a whole, I realised that plan was doomed to failure. The droughts of the last few years will become the norm within a couple of decades, and as this garden is intended to last for 100 years I have to assume those conditions in all my choices.

The dead tree bed is the farthest corner on my property from water access. I can reach it with a super-long hose if I set the nozzle to “fly high” and point-and-shoot from about six metres away with perfect parabolic angle, but that’s about it.

The adjacent corrugated fence presents a few challenges too. It is a thermal sink – albeit not too large – but on any warm day it’s radiating heat all afternoon. It does give shade, but it’s hot shade when the sun strikes the other side of it. And it makes a huge rain shadow too, given that much of our better rain comes from that direction.

The soil back there is poor even compared to the rest of its surroundings, and – like all of the garden – it’s off-the-scale water resistant, or hydrophobic. (Literally off the scale – I did the test myself and I couldn’t get any concentration of reagent to penetrate).

Put all that together and it’s no surprise the soil, or rather sand, is dry. Bone dry.

The weeds grow thickly in spring, but their stems are so slender and tough compared to their species-mates just four metres away you can see that it’s only the most-dry-loving variants that are surviving, and they’ve got all their epigenetic switches for drought turned to ON. (An epigenetic switch is something that turns genes ON or OFF based on external conditions such as drought, famine, malnutrition, poverty. Which genes are activated or silenced is never the only factor in how something grows, but it has an influence).

The saving grace of this space is the grape vine. Without it, this sand would sunburn. With it, although the ground stays bare and weedless all through summer, it’s not ‘cooked’. The seedbank remains alive. So I can make this area a seasonal meadow. The trick is to use plants that don’t need to germinate in autumn. It takes ‘til midwinter for the soil profile to get enough rain through it for young plants to survive.

I tried autumn sprouters the first year: flax linseed and quinoa, but no success. This year I’ve gone for garlic. This plant sprouts at midwinter, harvested or dies back in late spring / early summer and is done by the summer solstice. So it’s thriving in the light while the grape vine has no leaves, and then sleeping underground through the hot season. The timing is much better.

Of course, the soil is still crap. I have much work to do to make it able to convince plants that they’re not about to die, and even more work to do to replace the weeds I don’t want. So it’s an ongoing project. But we’ll see how it goes this year, and reassess methods and plan next year.

*Tiki Swain is interested in everything and pays attention to as much as possible, especially if it’s food, plants or primitive skills. She is a former science communicator, now studying urban farming and writing about the interplay within agricultural systems at AgriTapestry. You can find her on twitter as @tikiwanderer

First year biology

In October 2013 on October 23, 2013 at 9:13 pm

kirsti biology Spiral succulent

Kirsti: First year biology at university. Most Bachelor of Science students did it. I did it. It’s a prerequisite for many, more specialised second year units, and the foundation for other degrees like agriculture, food science, biomedicine and medicine, and sometimes environmental science.

I’ve been doing some lab and tutorial teaching of first year biology this past 3 months. It’s been rewarding. But I’m now launching into my first trimester of purely external (online) first year biology students at the University of New England.

I know. EXCITED!

The students will experience an intensive practical school to ensure they get into a lab, get their hands dirty, make observations of actual specimens and get to talk to other students first hand. But other than that, everything’s in their own time, at [mainly] their own pace, and – the killer – during the summer holidays of most university courses.

I’m looking forward to live chats about our topics, setting some fun interactive quizzes to get them thinking, but most of all, advising them to get out there and look around! They could, for example, look for evidence of symmetry in their own gardens, arthropods on their kitchen bench-tops and shared features of any vertebrate pets in their vicinity.

In my own head right now I might choose to go off on a tangent with thoughts and grumbles about various things relating to university study these days. Like the reduction of semester weeks to trimesters at some universities, decreasing the number of lectures, practicals and assessments in first year biology (primarily due to increasing student numbers and decreasing budgets), and superficial learning by generations of IT-savvy kids. But I will not force you to endure that. Not today anyway. 🙂 

Instead, I will continue writing my lecture on animal development, and marvel at radial symmetry, a developing gastrula, arthropod diversity and the existence of nematodes.

Day 272. Autumn in the garden

In May 2013 on May 12, 2013 at 5:00 pm


Autumn in the garden means citrus, very ripe quinces and new seedlings.

And an aberrant monarch butterfly – no doubt confused by a week of unusually warm weather.





Day 234. Elm beetle

In April 2013 on April 3, 2013 at 2:54 pm


My father-in-law is in a state of panic.

The leaves of his magnificent Golden Elm tree look like they’ve been shot with a small pellet gun.

Fortunately, our family gardening guru has nailed down the culprit to be the Elm Leaf Beetle, or Xanthogaleruca luteola.

The beetles are a native of Europe, and migrated across the world to reach Eastern Australia during the 1980s and 1990s. The wee blighters cause damage to elm foliage in two ways: the shotgun pellet-like holes result from adults having a chew, whereas the larvae leave a partially skeletonised leaf behind them. In severe cases, defoliation can lead to death of the tree.

Fortunately, professional tree servicers suggest

“one or two years of Elm Beetle damage or ongoing moderate damage is very unlikely to kill the host tree, unless there are other significant contributing factors.”

Settle down Pa.

Day 202. Garden update

In March 2013 on March 2, 2013 at 3:31 pm


My garden has somehow survived the hottest summer on record.

Although my two basil varieties are now going to seed (‘Italian’ and ‘Asian’, shown above), the quinces are nearly ready to pick, I hold high hopes for a singleton pumpkin and a new crop of figs ripens each day.


My mouth is watering at the thought of a new mandarins, which have just started to turn slightly orange.


Day 201. Umbilical pumpkin

In March on March 2, 2013 at 3:10 pm


Thanks to The Italian Gardener, I’ve been experimenting with vegetable planting.

In November last year I planted several new varieties in my above-ground steel tubs. One of the pumpkin seedlings grew like a weed, sending out runners way too long for the venue I had chosen. I pushed them into the garden bed on the side of my lawn.

Two flowers on the smaller runners were fertilised early in the season, and produced slightly unusual fruit which didn’t ripen properly.

A third pumpkin, which formed right at the distal end of the main runner, only started to swell in the New Year and is developing very nicely as I write.

One specimen, on the end of a 10 foot-long stem. I’m calling it umbilical pumpkin.

Day 197. Ripe for the Picking

In february 2013 on February 25, 2013 at 9:40 pm


In front of the rain tank at the bottom of my garden is a gnarled old quince tree.

In winter, it looks on death’s door. During spring, delicate green leaves and pinky-white blossom burst from the dark limbs. By November, juvenile fruits start to form at the base of each flower,  and these slowly swell to become green/yellow and fuzzy, with a strange, subtle odour. Fortunately, the birds don’t like them much – not until they’re overripe at least.  This which means we usually get full value from the crop, as I pick them in March whilst still relatively firm.

The photo above shows the quinces as they look at the moment – I simply love their appearance, and the promise of all the stewed fruit, jellies, cakes and crumbles which shall soon be created in my kitchen.

My favourite way to cook quinces is a la Stephanie Alexander: peel, chop, throw into an enamelled cast-iron pot filled with light sugar solution/vanilla/lemon juice/lid on and then cook in a slow oven (130 degrees centigrade) for about 8 hours. At which point they emerge as glistening segments of garnet surrounded by blood-like syrup.

The red colour emerges as a class of chemical compounds called anthocyanins are converted from their colourless, astringent precursor cousins the leucoanthocyanins during cooking.

Harold McGee in On Food and Cooking: The Science and Lore of the Kitchen says it best,

The combination of heat and acidity causes the subunits [of the precursor molecules] to break off one by one; and then oxygen from the air reacts with the subunits to form true anthrocyanins: so the tannic, pale fruits become more gentle-tasting and anything from pale pink to deep red.

The final colour depends on the pH (acidity) of the cooking fluid.

Anthocyanins are also what make blueberries blue, red cabbage red, blackberries black, eggplants purple and blood oranges bloody. According to some experts, we may get cardiovascular benefits or even cancer protection from eating more anthocyanins.

Day 175. Swallowtail

In february 2013 on February 4, 2013 at 12:44 pm


A very busy, stimulating weekend at the ScienceOnlineAdelaide WatchParty has left me so filled with thoughts that yesterday I simply could not condense a single blog post to wrap it all up.

Instead, I retired to my garden to play backyard cricket and take a few photographs.

The image shown above is of a swallowtail butterfly, captured as it flitted from leaf to leaf on a citrus tree in a large pot in my BBQ area. It was probably seeking to lay eggs.

As reported by, swallowtails are endemic in Australia, and current species evolved from ancestors which migrated from Gondwanaland/Antarctica about 40 million years ago.

Day 157. Paris!

In January 2013 on January 16, 2013 at 7:20 am


Paris, je suis la!

I’m staying with my sister and brother-in-law in the most divine apartment in the fourteenth arrondissement. Over the next 8 days we plan to eat, shop and prepare for the imminent arrival of my new niece/nephew.

But enough trivia, how about some science?

As I look out of the apartment window – in between snow flurries I might add – I can see the dome of l’Observatoire de Paris Perreault Building, a major site of astronomical observation and the architecture of which dates back to 1667.

A short walk up the road leads me to the Catacombs of Paris, established at the end of the 18th century in order to control the spread of infectious disease from The Cemetery of the Innocent.

If I jogged 1 kilometre towards the river Seine I’d be at Le Jardin de Plantes, equivalent to a botanical garden, and part of Paris’ Natural History Museum complex.

This is going to be fun.

[image thanks to zaps06 on flickr]