GROWING FROM SEEDS
|Growing plants from seed – how hard can that be? Well, time after time, I have experienced that it can cause problems. After years of experiments - and an education - I have learned some tricks which I want to share.|
One of the
common ways to get new plants into your garden or collection is to
obtain seeds. Especially in these internet-dominated years, tracing and
acquiring seeds from foreign countries or even finding them yourselves
abroad, are quite common.
The temperature can have an impact. In general, the water should be around 30C. Some seeds will react to electric conductivity (a way to measure the amount of nutrition), which in general should be keep around average fertilized water: 1000-4500µS. A slightly more scientific way to approach this, is to look into the osmotic pressure which should be kept between 30 and 150 mmol/Kg. You might say; this is a way to emulate a good growing site.
2) While this is sufficient for most seeds, some will require a bit more preparation. Many seeds have a membrane, controlling the moisture within the seed. To awake the seed, this might have to be penetrated. A simple way is to freeze the seeds. Either dry or in water.
While this is explainable and anticipated for seeds originating from habitats with winter frost, it can be surprisingly effective for some tropical seeds.
This is one
way to imitate the passing of the winter, letting the growth start in
3) Some seeds, typically originating from open plains, have a sophisticated “brake”: They wait for a bush fire. It was long believed it was the temperature alone that triggered them, and “baking” the seeds in an oven was the common treatment.
Recent research has proven that for some species, one of the components in the smoke is crucial. The butenolide - 3-methyl-2H-furo[2,3-C]pyran-2-one - in smoke induces germination.
There are several ways to obtain this. If the seeds are smoked or sown in pots, and the pots are smoked, it works. Another way is to soak them in water along with some smoked material like cloth or paper. The smoke can be produced by igniting some wet grass. This way, we emulate a bushfire.
4) By itself, or in combination with the former two methods, heat is a trigger. It not only breaks down the membrane, it also breaks down the hormones ( ABA ) that causes the seed to stay dormant. Some seeds seem to need extreme heat treatment to awake.
Extinct in the wild, Sophora toromiro from the Rapa Nui ( Easter Islands ) has caused problems. So far the best method is to let the seeds soak in 70-80C hot water for 24 hour.
For other species, in general nut-like seeds, a less drastically treatment can work. Put the seeds in a mug of freshly boiled water, and leave them until the following day. It is the equivalent of a long and warm summer in the sun.
5) While we are at the nuts, it is appropriate to mention the need for the nutshell to be penetrated, not only for germination, but for the input of water. For some species, sanding the shell is sufficient. Others need a more drastic approach. The nutshells might have to be cracked or drilled into. But make sure you don’t harm the embryo. This simulates the eating and passing through the stomach of a bird.
6) Some seeds are meant to be eaten. They require digestive the acids, and this can be simulated. Depending on the species, soaking them in sulphuric acid for an hour or two and washing them carefully afterwards can do the trick.
7) Many species await the coming of the rainy season. To make sure it is the beginning of a new season, they have to experience the dry time. It is, I admit, hard to tell how dry your seeds have become, but storing them in a closed box along with salt (but not in contact with it) for several months should do it.
8) The tiniest of seeds, like orchids’ often rely on the assistance of fungi. The seeds are this small to be distributed by the wind. The downside is that they are too small to contain the necessary nutrients for the embryro. They await the hyfe of a fungus, but rather than the fungus feeding on the seed, the seed feeds on the fungus. The tiny seed sucks out nutrition from the fungus until it has obtained sufficient size.
You might achieve this by adding fungi spores to the soil or re-using the soil from the mother plant. With the right equipment, sterile growth can be done on agar.
9) While some seeds are restricted by light, others require it. This has an impact on how deep the seeds have to be sown. Some seeds have to be exposed to red light (700nm), to start.
10) Time is a factor as well. While some seeds die real fast, others can live for millenniums. If none of the above treatments work, it might just be a question of time – and patience.
11) Maintaining the moisture, clearing the shell and stabilising the sprout, the seeds have to be sown in the right depth. In general, 3-4 times the size of the seeds is recommended. Too deep, and the seeds can be choked. They need oxygen.
By now, I believe you have some sprouts on your seeds, and you face the next hurdle: How to treat seedlings – but that's another story!