A MANUAL FOR GERMINATING SEEDS OF CHILEAN PLANTS

This is a summary of the procedures and techniques needed to successfully germinate the seeds and establish plants. The information here is based on three major sources: our own experiments, observation of the habitat and weather conditions, and literature. We will discuss the general aspects of germination and then there is also a list of genera and families and the corresponding treatments (under construction right now).

If you look on the world map the location of Chile, you may think that Chile is a very warm country having subtropical climate – the central parts it is at the same latitude as Northern Africa or Florida. Partially it is true, the temperatures in summer in central zone may reach as high as +35º C and in winter it rarely falls below 0º C. However, Chile is a country of high mountains, and the climate there is radically different – while the summer highs may still be warm reaching +25º C, the winter is long, and cold, with snow staying for several months, and temperatures dropping down to -20ºC. And about 70 % of all seed species we sell come from the mountains.

So there is a hot, dry season, followed by a transitional season, where it may be wet, but still warm, followed by wet, cold or very cold season, and finally the wet, warm spring. The seeds of plants “know” this weather pattern, and most germinate at the beginning of the wet, warm season when they have the best chances to survive. And they figure it out by “analyzing” the two environmental factors – humidity and temperature.   In simple terms, the time to germinate is after it has been wet and cold (+3º C+5º C) for a while (months)...

Rule 1: Most Species Need Cold Stratification Treatment

So the first rule is that most of species coming from Central and Southern Chile need cold stratification. Most species from the Northern mountains (Altiplano) also need cold stratification. Virtually all High Andean species from Central and Southern Chile need cold stratification. That is about 80% of all Chilean species. If a species does not need cold stratification, it will not be damaged by it. Therefore, if it is not explicitly stated otherwise, you have to do cold stratification!

There are many ways to do it.

The general procedure is to soak the seeds for 24 – 48 hours in cold water, ideally changing the water several times (if the water changes color, then it should be changed). The change of water may be necessary in order to wash out the germination inhibitors which may be present in the coating. Some species may benefit, if the water contains Gibberelic Acid (See rule 4 below). The seeds should be then placed into something which will preserve humidity. That can be humid sand, a towel or similar. Important point to bear in mind is that it must not be too wet (dripping wet; in that case the seeds may rot very easily), but humid, and it must not be sealed, because the seeds need to breathe. It is OK to use plastic bags with sand, provided you open them every few days. Volume wise, one part of seeds should go in three parts of sand.

For small quantities you can use small pots/plastic cups which you fill up with the growing substrate, then poor a layer of sand, place the seeds, then another layer of sand, and then cover the sand with a thin layer of sphagnum/peat moss or even with a humid paper towel. The sand is needed to prevent direct contact between the seeds and the possibly contaminated substrate, and the peat moss/paper towel will keep the sand moist. The thickness of the sand layer should be about 2 – 3 diameters of seeds. If it is too shallow, the seeds will end up in the substrate or on the surface, and if it is too thick, the roots may not be able to penetrate it. Place it in the fridge and check it about once a week for germination and for correct humidity (fridge tends to dry out the substrate). With this method, once the seeds germinate, you have the option to take them out of the fridge and keep them in the cup for a while, without risking loosing them, as is often the case with pure sand.

The duration of the cold treatment varies widely, and can be anywhere from 10 days to 3 months.  The plants coming from higher mountains usually need longer periods of cold stratification.

After cold stratification the seeds are (usually) ready to germinate at room temperature of about +20ºC and should be planted in the definite substrate.

Rule 2: Desert Species Germinate at Moderate Temperatures of +12 º C

There is a considerable number of species (about 20 %) which come from the coastal desert. In our database these are the plants which are earmarked as Region I, II, III, IV, Coastal Areas. Another earmark – Coastal fog.

It is a very special habitat, and requires a completely different germination strategy. The main environmental features of this area are: very stable temperature regime, with summer temperatures around + 14º C +20º C, and winter temperatures of +8º C + 18º C, high relative humidity, often foggy, and very rare precipitations.

Many seeds of plants from this area require the emulation of these conditions by the gardener. So...

First, the germination temperature must be kept at around +10º C +14º C. The germination occurs naturally in winter (rainy season) when the temperature is on the lower side. Some species simply will not germinate when above +16º C.

Second, the germination may take time. The seeds are adapted to wait for years, even up to a decade to germinate. The seeds “fear” germinating too fast, because germinating due to a stray rain shower at the height of the summer (dry season) will definitively kill any hope to survive. So there should be a continuous exposure to humidity, maybe with some drying in-between.

Therefore, the seeds should be watered profusely for about 15 days. In fact, this process can be started by letting the seeds to soak in water for several days before planting (at least two and up to four days). There is an excellent article (in Spanish), Abiotic factors effects influencing the germination of six herbaceous species of Chilean arid zone, where the authors demonstrate this for five of the six species they have tested. For instance, if no soaking at all was used, the germination was between 5% and 15%, whereas for soaking over 96 hours, the germination rate was between 25% and 60%, depending on the species. The response to temperature was more variable, and two out of five species had a slighly better germination at 25ºC (30%) than at 10ºC (15%), however, three species which had 35-70% germination at 10ºC had 10%, 15%, and 30% germination at 25ºC and less than 20% at 30ºC. To put it short: low temperature is much safer for geminating desert species, although some species might have slightly better response to warmer temperatures. Presoaking the seeds improves drastically the results.

If the seeds do not germinate, give them a break, let them dry a little bit (but not over drying, cover the pots with plastic or similar to preserve high environmental humidity), then continue watering from time to time.  If it still does not work, play with the temperature, making it oscillate in the range of + 8º C and +18º C. Some seeds, even under the ideal conditions, may take as long as 12 months to germinate. Especially the plants of II Region are known to be very difficult to germinate.

Rule 3: Some Seeds Require Scarification

All seeds of the fabaceae family (in Chile, mainly Adesmia, Astragalus, Caesalpinia, Lathyrus, Prosopis, Sophora, Vicia) and some other species have very hard coats (testa) which protect the embryon. The positive side of this is that the seeds retain viability for decades, some species even up to half a century (for instance, Sophora cassioides). The downside is that unless you break this coating, the seeds will not  germinate. It may take up to several years in nature to break this coating.

There are three ways to do: mechanically, chemically, and by heat.

For small quantities of seeds we recommend doing it mechanically. Although it may be slow, it is very safe (both for humans and seeds). You have to use nail clippers or scissors to cut away a piece of seed coating. Choose an area on the “back” of the seed, away form the embryon, and chafe away the superficial skin. You should not cut into the seed (applying pressure may damage it), just scrape it. Ideally, a very thin coating flake should come off. To see if you are doing right, put the seeds into water. If you have scraped off enough, the seeds will bloat up in about 24 hours. The bloated seeds after 24 hours in water are ready for planting.

For larger quantities of seeds, the manual scarification is not really feasible, and one can use the sulphuric concentrated acid. The procedure is straightforward – the seeds should be placed in concentrated sulphuric acid; the immersion time may vary considerably from a few minutes to two hours. Then the seeds should be rinsed in running water for about 30 minutes. This is dangerous, because if water is poured into acid, it will boil up and splatter! The length of the exposure must be determined experimentally, by germinating or soaking (quick method) the treated seeds. Overexposing may result in damage to embryos (seeds will still swell in water, but they may be dead).

We do not recommend heat as a means of breaking the seed dormancy. Australian Fabaceae species are known to be exposed naturally to fires. In Chile, there are no natural fires, so that the species of the fabaceae family are not used to be baked. If you still want to proceed with this method, the times and temperatures necessary to break up the testa may vary considerably and require experimentation.

Rule 4: Some Seeds May Benefit from GA (Gibberellic Acid)

Many species which have dormancy may benefit from exposure to Gibberellic Acid. Nothofagus, Fitzroya, Austrocedrus, Peumus genera are explicitly known to benefit from it.  Also, any other hard to germinate seeds, including the seeds from coastal desert may benefit from exposure to it. However, there is no hard data available for most of the Chilean plant species.

Prepare a solution containing about 300 to 500ppm of GA.

First, prepare a stock solution of 1000ppm. If you use pure (100 %) GA, then use 1 g/1 liter or 100 mg per 100 ml. You can often buy tablets which have only 20 % or 40 % of the ingredient (see label). In that case you simply have to increase the weight of the tablets, 5 g/l for 20 % and 2.5 g/l for 40 % tablets. To obtain a 500ppm solution, dilute the resulting solution  by half (i.e. add same amount of water, for 100 ml stock solution add 100 ml of water). For 330ppm, add 2 parts of distilled water to one part of stock solution.

Soak the seeds for up to 24 hours in this solution. Then continue with the normal cold stratification if applicable or sow directly in case of desert species.

Rule 6: Depth of Sowing is Very Important

Most seeds should be sown at a depth equivalent 2 to 3 times their diameter. However, there are many species which germinate better or germinate exclusively under light conditions. So...

All small, powder-like seeds must be sown superficially. This includes especially Calceolarias, Nicotiana, and Hydrangea.

In addition, Puyas also need light for germination.

Rule 7: Recalcitrant Seeds Must be Sown Immediately

Some species are recalcitrant, meaning that they can not be dried out and stored. Fortunately, Chile has few species which belong to this group due to its dry climate (the recalcitrant plants could not survive these dry conditions). The seeds of this group are partially dried for shipping, but retain enough humidity to continue to be viable.

Once you receive such seeds they must be planted immediately. It is a good idea to let them soak in water for a few hours before planting.

All Myrtaceae seeds (Amomyrtus, Luma, Myrceugenia, Ugni) belong to this group, also parasite Tristerix, Drymis,  and partially Philesiaceae, which include Lapageria rosea, Philesia magellanica, Luzuriaga. The latter group can still be germinated when dried, but it is much more lengthy and complicated process. When fresh, the Philesiaceae seeds have about 80 % germination rate.

Rule 8: Orchid Seeds Need In-Vitro Propagation Techniques

There are many beautiful orchid species in Chile. However, unless you are familiar with the general procedures and have successfully grown orchids from seeds, do not try them. The success rate when sown like normal seeds is a guaranteed 0 %. You will need sterile working environment (laminar flow hood) and procedures to obtain results. Compared to other orchids, the Chilean orchids are not especially difficult, and standard Murashige and Skoog solution seems to work well.