As unorthodox as it sounds, this is where you use Salts to increase germination rates and resulting plant vigour.
While salt can definitely kill plants, and salting the earth is never a good idea, this really does work for a heap of different species. Once you wrap your head around the science it makes perfect sense too.
Solvents are things that dissolve stuff.
Paint thinner melts paint, acetone used in nail polish remover dissolves and removes nail polish, and water is a solvent too as it dissolves things like coffee, powdered milk, dirt in clothes, you get the idea.
It also dissolves the chemicals naturally contained inside seeds.
Osmosis.
Osmosis is the movement of a solvent (such as water) through a semi-permeable membrane (such as a living plant cell) into a solution of higher solute concentration.
This tends to equalize the concentrations of solute on the two sides of the membrane.
Depending on the internal and external pressure, the internal or external cells will swell or shrink.
Think of it like this.
Imagine you have Container 1 and it has a lot of salts. Container 2 has no or very little salts.
If connected by a thin permeable(leaky/sieve-like) membrane(skin/barrier/cell wall) and then allowed enough time, Container 1 and Container 2 would both end up the same concentration.
It wouldn’t be heaps of salt in Container 1 and no salt in Container 2 anymore, it would eventually be a medium amount of salt in both containers.
Another good example is freshly written ink or a freshly painted picture that you spill water on.
Instead of nice dark lines with straight crisp edges, you just end up with a big grey smudge as the pigments and dyes evenly travel and disperse through the liquid on the page.
When things are connected by a permeable membrane, this allows or prevents the intake or expulsion of chemical components.
Cool, with me so far?
If so the next bits super easy I promise!
So, if you soak a normal seed in normal water, the cells take up that water, and it reacts with chemicals inside the seed and if the stars align just right, then you have germination!
Two different examples below.
- Germination triggered by chemicals being CREATED within the seed.
Example: seed stuff + water = waterystuff.
It is not water, and it is not stuff either. By soaking the seeds in water you have created a brand new chemical called “waterystuff” which is a mixture of the two.
Now that the plant has detected this new chemical it now knows it is a safe time to start the germination process. These plants species are normally easy to germinate and they make up most of our common vegetables.
- Germination triggered by chemicals being leached out and REMOVED from the seed.
Example: water + seeds = brown soupy water + fat germinating seeds.
The water has dissolved the tannin’s or other natural germination inhibitors(sprout stoppers) in the seeds. Once leached out and removed, the seed is then able to germinate with nothing stopping it. If you left the seeds in a cup of the brown soupy water they will never ever germinate. Instead, they will just rot and die. This is because the germinating inhibiting chemicals are still there in the water, and they are in very close contact with the seeds in the cup. BUT, soak the seeds, then pour off the brown soupy water that has the germination inhibitors. Then refill that cup further diluting the last little bit of those chemicals and the seeds will shoot immediately!
They work like this because if the seeds sprouted in the very first Spring/Summer showers, the sun would cook them, or the still very Winter hungry wildlife would eat them immediately. But if the ground gets a good soaking, several times, the chemicals inside the seeds can then wash away. The plant knows the true wet season has fully arrived, the local wildlife has lots of other food available, it is now a pretty safe time to grow. Much better than any other time in its life.
This super-specific set of circumstances may take many years, decades with some species, and that’s where halo-priming can help!
Halo priming can open up the seeds cells, and allow more chemicals in.
In some cases just getting water in through a hard seed coat is difficult, but with the help of salts it is made easier as they naturally love to travel through walls and equalise the pressure differences.
Once allowed access, it means chemicals that stop germination can begin to be leached out, often in a much faster time than if the situation was a natural occurrence like flooding rains.
This rapid expansion and contraction of cells can simulate several rain and dry seasons all at once.
The seeds may even be tricked into thinking it has been many years since the seeds first fell to the ground.
The rapid change in osmotic pressure caused by soaking in salty water, then fresh water can be a really effective trigger for germination. So yeah, it can definitely make some species shoot way faster, for sure, decades earlier in some cases.
That alone is awesome news!
Even better, it can simulate stress and drought conditions, and a long age, followed by temporary good times.
The seeds believe it has been a long hard bitter year or years, and now it is finally the time to germinate, but they better do it quickly, and they better toughen up at the same time. The plants that do germinate handle later drought stress many times better than average, as they are already aware that drought may be an issue in the future.
They also grow much bigger requiring less fertiliser and water and this natural phenomenon has been known for ages!
Darwin did experiments showing that soaking lettuce seeds in seawater before germination produced a better germination rate, a faster later growth, and a heavier overall plant.
It also removed the need for sunlight as a stimulant for germination.
Many Lettuce~Lactuca species will never sprout if left in the complete dark, but with a salt water soak first he found they will without the need for sunlight. Not only that, they will be tougher plants that produce more leaves compared to untreated plants.
This is super exciting stuff and well worth exploring!
Traditionally urine or seawater are the two main chemicals used, but the main salts used commercially that you can easily get your hands on at home are as follows:
- Potassium nitrate (KNO 3). Contains 14% nitrogen and 46% of potassium oxide (K 2 O).
It is found as a mineral nitrate and is a natural source of nitrogen used extensively in fertilisers, preserved meats, and explosives. Sometimes called “Kalio Salietra” and it is sold in boutique butchers and delicatessens.
If you suddenly order a pallet of the stuff it will definitely raise red flags with the boys in blue, but small sensible amounts are used by gardeners and home butchers all over the country without any dramas. - Magnesium sulphate ~Epsom Salts. This activates the enzymes in the seed which break down the inbuilt food supply so the plant will germinate quickly. Supermarkets commonly stock very cheaply but make sure it is pure form, not full of colour or frangrances.
- Calcium chloride. It’s an inorganic salt with the chemical formula CaCl₂.
It is a colorless crystalline solid at room temperature, highly soluble in water and is commonly used for making facial masks and in cheese. - Table salt, common, or sea salt is a mineral composed primarily of sodium chloride (NaCl).
Table salt also contains 0.002% to 0.004% iodine but at those levels it makes no real world difference.
Halopriming Method.
The method is super simple but relatively new to most folks. It is especially effective for our hard to grow, less common, Australian native plant species! All you need to do is soak seeds for various times, in various concentration percentages, of various salts.
Always have control groups that are just plain water so you can compare the results. Without a control you can’t see if it did or didn’t help, and if so by how much?
- 2-5% is a good start point for salinity.
- 12-48hrs is the normal soaking time.
- 12-48hr rinse soak is also often used. It is a good idea to test if that is helpful or not as in my trials it has shown to be very species-dependent. It makes some things way better but it also makes some things worse.
Example of a trial.
- Group 1.
Soak seeds in water for 12hrs before planting. - Group 2.
Soak seeds in water for 24hrs before planting. - Group 3.
Soak seeds in water for 12hrs before removal.
Soak seeds in new clean water for 12hrs before planting. - Group 4.
Soak seeds in X salt at 2% for 12hrs before planting. - Group 5.
Soak seeds in X salt at 2% for 12hrs before removal.
Soak seeds in new clean water for 12hrs before planting. - Group 6.
Soak seeds in X salt at 5% for 12hrs before planting. - Group 7.
Soak seeds in X salt at 5% for 12hrs before removal.
Soak seeds in new clean water for 12hrs before planting.
If you are not happy with the results then you can do it all again using a different type of salt, or different soak times, or exactly the same thing but at a different concentration of salt. Every species is different, and if you are the only dude doing the experiment then there are no hard and fast rules to follow.
That’s what makes it so exciting!
Another chemical worth considering is Zinc sulfate(ZnSO4).
It is an inorganic compound and dietary supplement. You can find it as a supplement sold in pill form at every pharmacy and health food shop in the country and it is used to treat zinc deficiency and to prevent the condition in those at high risk. It can also be bought in pure form from chemical supply companies very cheaply.
Some folks are currently experimenting with halopriming using this, and some are getting pretty amazing results, but handle with care as side effects may include feeling tired, abdominal pain, vomiting, headache and like most things Zinc overdose can also kill you…
If you ever see anything cool happen especially with any rare or very hard to germinate species I would love to hear about it!