Friday, 28 September 2012

carob tree // st john's bread

order: fabales
family: fabaceae
genus: ceratonia
species: siliqua (is there any possibility that it's a C. oreothauma?)
cultivar: from seeds obtained from a wild parent tree


When a friend of mine returned from the trip to South Africa earlier this year, he gave me different seeds he collected during expeditions in the wilderness including a seed pod collected from a carob tree. I have seen carob seed pods sold in supermarkets as food, but I don't know if there are still viable seeds in them. I have my seeds, so I probably don't ever have to find out.

On one fine day in July, I opened up the very hard pod and strained a lot of energy doing it. Since I didn't want to do damage to the seeds, I didn't want to use a knife. Instead I cracked it to bits with my bare hands. Seeds could then be knocked out from the pod. Next, I soaked the seeds in water for over 24 hours until they swelled. After that the seeds were sown in a pot of a standard potting compost. They sprouted in a couple of days, all of them. Since it belongs to the pea family or the legumes (fabaceae) -- a popular family of plants including acacia, mimosa and wisteria -- you can expect pinnate leaves on the plant. So far there are only two leaflets on each leaf. Young shoots are bronze in colour and turn dark green afterwards. The stems of the new shoots are thinly winged. The foliage is rather stiff and shiny. If you want to have any fruit at all, keep at least one male and one female plants. Yes, they are dioecious. I read that the flowers are initially bisexual or hermaphrodite. One sex will be suppressed in later development. So it's a good idea to keep several seedlings until the sexes have been determined.

As always I do things at the wrong time of year. Only two months after germination those sunny summer days are all over. Now we are already getting into autumn. Average temperature dropped down to 10°C in my area. So I brought the seedlings into my studies so they can continue to grow a bit more before the days get too short.

Carob trees grow best in calcareous soils. They should be kept above freezing temperature at all time. Water moderately and let dry out almost completely in between. It's unclear whether carob tree is able to fix nitrogen from the atmosphere. However it seems like they do not have the nitrogen fixing nodules present on some other leguminous plants. Assuming that its ability to fix nitrogen is weak, I believe it will be beneficial to give potted plants some weak balanced fertiliser occasionally. This should give the plant sufficient nitrogen and thus eliminate the need to use mycorrhizal fungi, which probably drains more energy from the tree than the tree can produce in low light condition in the winter, especially if the overwinter temperature is high enough for the fungi to stay active. As a rule I'd only use mycorrhizal fungi on plants that stay outdoors year round.

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