The Biosphere Blog

New Jujube Cultivars

kristi — Tue, 14 Apr 2026 02:45:00 +0000

This season we will have:

GA 866, a large ovoid-shaped fruit about 5 cm long, and with a very high sugar content.
Mid to late-season ripening.
Good for both fresh eating and drying.

Honey Jar, small but with a very juicy crunchy taste.
Very early-season ripening.
Excellent for both fresh eating and drying.

Hulu, a very unusual jujube which looks like a miniature gourd with a pointed tip. A sweet, juicy and crunchy taste.
Mid-season ripening.
Excellent for fresh eating.

Millstone, a similar gourd-like shape like Hulu, but with a more flat, rounded bottom. A sweet, juicy and crunchy taste.
Mid-season ripening.
Excellent for fresh eating.

Porterville, like Chico in shape and taste, but larger and with lobes like a pumpkin.
Early to mid-season ripening.
Good for both fresh eating and drying.

Russian #2, from southern Russia. A small, compact tree well-suited to smaller areas. The fruit is small like Honey Jar but slightly more elongated. Sweet, firm and crisp.
Early to mid-season ripening.
Good fresh eating.

Sugar Cane, a medium-sized, sweet and crunchy fruit.
Mid-season ripening.
Excellent for both fresh eating and drying.

Tiger Tooth Early, a long wide oval shape more incisor-like than Silverhill, which is molar-shaped and also known as Tigertooth. (I call ‘Silverhill’ ‘Tigertooth Late’ so as to avoid confusion with ‘Tiger Tooth Early’ —note too the difference in spelling of ‘Tiger Tooth’ vs ‘Tigertooth’.)
Quite sweet, similar to Honey Jar.
Early-season ripening.
Excellent for both fresh eating and drying.

These, along with the regulars (Chico, Li, etc) can all be ordered for bare-rooted winter delivery here.

Updated Further: What Would You Make of This Tree?

kristi — Tue, 14 Apr 2026 02:21:00 +0000

Updated: The Si-Hong from This Previous Update of This Post

This all began on 1st October 2024, when I first mentioned this little Si-Hong:

Baby Si-Hong jujube tree in 190 mm diameter pot
© Optimate Group Pty Ltd

Which by December that same year looked like this:

Fruiting branchlets on Si-Hong jujube tree
© Optimate Group Pty Ltd

In that post I mentioned how its sole mother fruiting branch was the reason for it having three fruiting branchlets and not advancing in height. I also stated:

It is easy to see why people not used to these trees think their tree is a dud — and a dead dud at that! — that first winter. But come the following spring, with their tree now settled in, there is every chance an extension branch bud will shoot and cause that tree to double and sometimes even triple in height in just weeks.

Sure enough, that following year (spring, 2025):

New extension branch on Si-Hong jujube tree
© Optimate Group Pty Ltd

Rapid growth out of nowhere, with an unrecognisably much taller tree. This is soooo typically jujube!

Here is a more recent photo, taken on 16th March this year 2026 — not looking its best as it’s slowly winding down for winter dormancy:

Si-Hong jujube tree, March 2026
© Optimate Group Pty Ltd

Again typical for a jujube tree, once settled and having put on some height, it was quite content to work on some lateral growth:

Si-Hong jujube tree, March 2026
© Optimate Group Pty Ltd

The photo below is at an angle, but the branch at about one o’clock is an extension/permanent branch and the others are secondary branches:

Si-Hong jujube tree, March 2026
© Optimate Group Pty Ltd

The Overdominance Phenomenon in Warfarin-Resistant Rats

kristi — Mon, 13 Apr 2026 11:23:00 +0000

(This article was originally posted here on The Wollongong Nursery Blog.)
First published here 13th April 2026.

(This article is loosely based on one originally published 15th March 2019 here on an animal breeding blog I wrote from 2017-2019. Every single image in that blog, including the maths ones, was drawn or written by me.)
This modification published here 4th March 2026.

The warfarin molecule
Attributed to Calvero, Public domain, via Wikimedia Commons

This post came to mind following the recently revised An Effective, Homemade Rodenticide.

It was only intended to be short, in a “fun factoid” kind of way, but like everything in science, requires some background knowledge in ground-level genetics.

So that didn’t happen, but here goes anyway!

Genetics courses always begin with Mendelian inheritance, named for (not by) Gregor Mendel, who first observed and described this pattern of genetic inheritance in the culinary pea Pisum sativum. Mendel was an Austrian monk who began this groundbreaking work in 1858 and published his findings in 1866. This work sadly went completely unrecognised until its rediscovery in 1900, sixteen years after his death in 1884. Mendel is now regarded as the father of genetics.

Very, very simply, Mendelian inheritance is about dominant and recessive genes.

Anything with two copies* of a dominant gene** will express the dominant trait, and can only pass the dominant gene to its progeny. We say this organism is homozygous dominant and has a homozygous genotype for the dominant gene.

* This is what people learn, but in the plant world it is very common for many species to have multiple copies of a gene. Six, eight, or even more copies is not unusual! This polyploidy complicates things exponentially and will be skipped over here.
** The more accurate word here is allele, or version of a gene if you like.

Anything with two copies of a recessive gene will express the recessive trait, and can only pass the recessive gene to its progeny. We say this organism is homozygous recessive and has a homozygous genotype for the recessive gene.

Anything with one dominant gene and one recessive gene expresses the dominant trait, but can pass either gene to its progeny. We say this organism is heterozygous dominant and has a heterozygous genotype.

This is classic Mendelian inheritance, and introductory genetics pretty much ends there.

But as genetics became a scientific field in its own right, and more deeply studied, it soon became apparent that not every inherited trait followed this simple pattern.

Some patterns of inheritance made no sense whatsoever until the concept of non-Mendelian inheritance was realised.

There are many types of non-Mendelian inheritance: partial dominance, codominance, sex-linked inheritance, epistasis, polyploidism, and several more besides.

Today’s post on rat resistance to warfarin is due to an interesting form of inheritance known as overdominance. It follows Mendelian inheritance, and yet doesn’t, making it too a form of non-Mendelian inheritance.

Overdominance is the phenomenon whereby the expression of the heterozygote outperforms that of the homozygous dominant genotype, and rat resistance to warfarin is an excellent example of this.

Warfarin thins the blood and prevents blood from clotting, and in high enough concentrations will cause fatal internal bleeding. Vitamin K is a blood-clotting agent essential in the diet and counters warfarin’s action.

The gene for warfarin resistance in rats is dominant, and both heterozygotes (one copy of the dominant gene) and homozygotes (two copies of the dominant gene) for this gene are unaffected by warfarin. However, rats homozygous for warfarin resistance need a higher level of vitamin K than they can get naturally. Thus rats homozygously not resistant to warfarin as well as rats homozygous for resistance will both succumb to warfarin. Those that are heterozygous for resistance do not succumb. The warfarin-resistant gene is overdominant with respect to rat survivability: rats heterozygous for warfarin resistance outperform (survive) rats homozygous for warfarin resistance.

Overdominance in general may also explain the phenomenon of hybrid vigour, also known as heterosis. One possible reason could be that some genes (really the alleles, or versions of a gene) from one breed override the corresponding, more harmful, alleles of the other breed, and vice-versa. Collectively these may improve the hybrid’s overall performance (its “vigour”), and cause it to outperform its homozygous purebred parents.

Some cattle breeds are routinely crossed for this “best of both breeds” outcome — the crossbred Black Baldy in Australia is just one example. It is a cross of Hereford bulls with Aberdeen Angus cows, and the offspring tend to be healthier, faster-growing, of better maternal instinct, and are often more productive, and for longer, than their purebred parents.

PLEASE Say NO! to SGAR Rat Poisons

kristi — Mon, 13 Apr 2026 11:23:00 +0000

(This article was originally posted here on The Wollongong Nursery Blog.)
First published here 13th April 2026.

Have you ever heard or seen tawny frogmouths, boobooks, or barking owls at night (we do!)? This post is for them, with much thanks to NP for sending me this following the An Effective, Homemade Rodenticide post.

SGAR rat poisons are Second-generation Anticoagulant Rodenticide poisons and they are killing wildlife and pets. Warfarin and Coumatetralyl are first-generation anticoagulant rodenticides.

Second-generation poisons bioaccumulate, while first-generation poisons are fully gone from an organism in weeks.

The image below, is from this page:

You can also download that image as a print-quality A4 poster from that page, or directly here.

The Birdlife Australia ““What to buy and what to avoid!” page lists alternatives to SGAR poisons, including one made by Ratsak with natural ingredients! This one, called Ratsak Naturals, is widely available and is made from corn gluten meal and sodium chloride. It works similarly to my homemade one, in that it forms a mass rats can’t expel.

Sodium chloride is simply table salt. I had to look up ‘corn gluten meal’ as corn doesn’t contain gluten. Corn gluten meal is indeed not gluten, but is the main protein in the endosperm (corn kernel). It is a byproduct of processing corn and used as an animal feed. It isn’t cornmeal, or what we’d call “polenta’ in Australia.

I can’t determine the exact cause of death. This patent claims (with great detail) suffocation as the cause. This page claims (also with great, but different detail!) dehydration.

Other SGAR-related articles on the Birdlife Australia site worth a read (and perhaps act on?) are:
The evidence against SGARs
Protect Aussie birds from dangerous SGAR rat poisons.

Great news! It looks like (some, at least) SGARs will soon be pulled from shelves. A big win for owls, nightjars, quolls, Tassie devils, goannas, snakes and any other rodent-eating Aussie critters!

An Effective, Homemade Rodenticide

kristi — Mon, 13 Apr 2026 11:22:00 +0000

(This article was originally posted here on The Wollongong Nursery Blog.)
First published here 13th April 2026.

When you have fruiting trees, or grow other food, or have chickens, or feed wild birds, you are inevitably going to attract rats and mice.

Like homemade white oil, this rodenticide too is dirt-cheap to make, highly effective, lasts forever, and rats and mice cannot develop resistance to it.

Update: 18th March 2026
Please read about Second-generation Anticoagulant Rodenticides (SGARs) and their threats to wildlife and pets here.

First, the recipe:

One part rolled oats to one part plaster of Paris. What constitutes a “part” isn’t as important as the ratio of one to one — it all comes down to how much you think you’ll use or wish to store.

Add to a container with a lid, and toss/roll well until both ingredients are evenly mixed — I find this surprisingly not as easy to do as it sounds, as the fine plaster keeps settling out, leaving way too many oats on top. But persevere and it will pay off!

Update: 27th February 2026
I now use sugar instead of oats. The finer grains are similar in size to the plaster of Paris and the two mix so much better. It’s effortless. I don’t recommend oats as your first choice unless that is all you have to hand.

This photo is now redundant, but an oat-plaster of Paris mix should look something like this:

End update

You could also substitute oatmeal or a flour and sugar mix for easier, more even mixing. Powdered (sweetened) chocolate (not cocoa which is bitter) is also said to be irresistible to rats and mice. But do keep to the 1:1 ratio.

Another alternative, though messier, option, is to mix one part peanut butter with one part plaster of Paris, and roll into balls.

How to use:

Add any amount to any-sized shallow container rats and mice can access, and place in dark corners or along walls and other crawl spaces under cover where they are likely to travel. Under overhanging rocks and tucked between crowded pots can work too — anywhere a rodent is likely to hide and seek shelter from threats to it.

Update: 27th February 2026
Make sure these containers are not exposed to rain, hoses, sprinklers, or anything else that will wet the mixture. Water will set the plaster of Paris before it is ingested by rodents, rendering it inactive. (See next section.)

How it works:

The oats, oatmeal, flour-sugar combination, powdered chocolate or peanut butter is the irresistible bait to entice rodents to consume plaster of Paris. It is the latter which is the rodenticide.

Plaster of Paris is heated gypsum. Gypsum is calcium sulfate dihydrate (CaSO₄.2H₂O), and when heated to 120–180 °C becomes gypsum plaster, or plaster of Paris. This is calcium sulfate hemihydrate [(CaSO₄)₂.H₂O].

Gypsum hardens on contact with water, and thus the plaster of Paris hardens inside a rat’s or mouse’s stomach or further down in the digestive tract. This blocks their gut and acts in two ways: one by preventing further food digestion and one by causing bloat. Rodents can’t vomit, can’t otherwise expel the mass, and have an urge to take on more water, which just exacerbates their condition.

Apparently death is relatively quick, as in 2-4 hours.

Important:

It goes without saying to not place this bait where children, pets and bird visitors can access it!

It is also important to ensure this mix remains dry at all times, as otherwise it will set.

Fruit Protection Netting

kristi — Sun, 12 Apr 2026 12:16:00 +0000

(This article was originally posted here on The Wollongong Nursery Blog.)
First published here 2nd April 2026.

By far the best all-round pest control method is to simply exclude them. This is of course often easier said than done, but for many many set-ups exclusion netting is the most efficient and practical way to ensure pests never get anywhere near your fruit trees or vegie crops.

Nets with a large mesh size are great for keeping birds, bats, possums, kangaroos and other large animals out. But to exclude absolutely everything, go for nets with a small mesh rated for fruit-fly, cabbage moth and other insects. If they keep those out, they’ll also keep smaller animals such as mice and rats out, as well as, by default, all the larger ones.

You may not known that this kind of netting comes in a range of sizes, from bags to large nets, to suit all purposes. Let’s go through these now.

The Netting Material

All netting described below is made from the same 2 mm weave, which is non-toxic, UV-stabilised, lightweight, reusable, breathable, washable, and with a shade rating of 20%.

This netting excludes all insects including the dreaded fruit-fly and cabbage moth — as well as birds, mice, rats, bats, possums, wallabies, kangaroos, dogs, cats…

Fruit Protection

SMALL Fruit Protection BAGS (15 cm × 25 cm)

These small bags come in packs of ten.

Each bag has a drawstring with which to securely fasten it around small clusters of fruit on, for example, young jujube trees, or around single, large fruits such as apples and peaches.

You could also use a single bag as in the photo, as a mini net to completely cover and protect a young, small plant such as that jujube tree above!

LARGE Fruit Protection BAGS (30 cm x 30 cm)

These larger bags also come in packs of ten and have drawstrings.

The size is great for young-but-older trees with larger fruit clusters. These were life-savers on my taller jujube and fig trees.

And again they can be used as a mini net to completely cover and protect a young, but taller tree.

LARGE Fruit Protection SLEEVES (30 cm x 90 cm)

These large sleeves come in packs of five and have drawstrings at both ends.

A drawstring at each end enables you to position and secure the sleeve anywhere along a branch, and the large size ensures good coverage of fruit-heavy branches within a single sleeve.

Being able to access either end at any time is also very helpful when the fruit at one end are green but ripe at the other!

One very mild criticism I have with the sleeves — which I’ve not noticed with the two bags above, is that sometimes one of the drawstrings is not positioned well. If not noticed in time you may lose one of the ends inside the seam and it’s a very fiddly procedure to feed it back through. I don’t bother, but pull the whole string out and secure the bag by wrapping the string around the outside as in this photo:

Sometimes it makes for a more secure fit anyway!

This size was invaluable for my young but tallest jujube trees and for the fruiting branches of my younger but wider fig trees.

The jujube trees were more narrow and upright than the figs, and I used many of these sleeves as nets for complete coverage:

The drawstring was long enough to help secure trees to stakes as well!

These bags and sleeves are available via the links below::
Ten-Pack of SMALL Fruit Protection BAGS (15 cm × 25 cm)
Ten-Pack of LARGE Fruit Protection BAGS (30 cm × 30 cm)
Five-Pack of LARGE Fruit Protection SLEEVES (30 cm × 90 cm)
Bag and Sleeve Combo

Suimen Smiley Leaf

kristi — Sat, 11 Apr 2026 07:55:00 +0000

(This article was originally posted here on The Wollongong Nursery Blog.)
First published here 11th April 2026.

Smile! This is a Suimen jujube leaf, 100% a legit photo taken by me and not AI. (That I need to say that at all is so depressing….)

This ability of us to perceive objects that aren’t there is called pareidolia.

Updates on Recently Featured Trees

kristi — Thu, 30 Oct 2025 09:49:00 +0000

This post is of updates of three previously mentioned trees:
a Si-Hong which featured in What Would You Make of This Tree?, first posted on 1st October 2024 and with a follow-up on 13th December 2024 here; and,
two cuttings which featured in Miraculous Jujube Cuttings, Plural!, first posted 21st January 2025 and with a follow-up on 18th February 2025 here.

The Si-Hong

The Si-Hong just over a year ago began the 2024 season as this runty little thing I couldn’t help but love:

and which went on to grow these fruiting branchlets:

Which, being deciduous, all fell off over winter this year 2025, and so this little fella again looked as he began (I never took a photo, so yes, this is simply the same photo as the first one above, for effect!):

In the 13th December post update, I wrote:

But come the following spring, with their tree now settled in, there is every chance an extension branch bud will shoot and cause that tree to double and sometimes even triple in height in just weeks.

Well, a year later it is that following spring, and would you look at this!

I didn’t even notice this until two days ago. It just shot out of nowhere, as they do! Runt no more — that new, permanent extension branch has now not quite tripled the height of this tree in a few short weeks.

Here’s a close up of the extension branch coming out of the mother branch:

The very thin stems coming off that are this year’s fruiting branchlets, and you may even be able to see the flower buds forming on the upright one closest to the camera.

The Two Cuttings

Back in August 2024 I discovered two sole surviving cuttings from at least sixty failed others — jujube trees are notoriously difficult to strike from cuttings, like Japanese maples. These two were, quite frankly, miracles, as it wasn’t from years of trying countless other times. Here they are on 21st January 2025:

and four weeks later on 18th February 2025:

The stronger cutting was labelled a Silverhill, and went on to develop Silverhill fruit (can you see where leafcutter bees have been?):

which I think the Satin bower birds took. The weaker cutting never fruited and I have no idea which cultivar it is, as I actually fished that piece out of the compost after having a change of heart and giving it a chance would you believe! (All the others I fished out went on to fail of course.)

I didn’t dare touch them that first season, but they couldn’t stay where they were another year, and so I re-potted them when they entered dormancy last winter 2025. I was very pleasantly surprised by the root mass, and while they look dwarfed in these 9 L Air-Pot containers, the roots justified this size and I felt an Air-Pot gave them their best chance to develop further.

The delicate roots were probably a bit put out by the handling — and despite every care some roots on each did come away — but each cutting did reshoot this spring 2025. Here they are on 28th October 2025: