November 2012


Most people know of the tomato tree, but there is also a plant called the cucumber tree, which is endemic on the island of Socotra which belongs to Yemen, but lies closer to Somalia than to the Arabian Peninsula. It was discovered by Sir Isaac Bayley Balfour in 1882. It is extremely rare in cultivation with very few nurseries offering it for sale. It is a monotypic genus in the family of Cucurbitaceae and the only tree in the family, the rest being climbers. The temperature on the island is always more than 20°C, also at night, therefore this plant requires a high temperature in the greenhouse to grow. It can survive at lower temperatures, 15°C minimum, but it won’t grow well. It also prefers bright light, but will tolerate some shade. It can take a lot more water in the growing season, but be careful not to overwater it in the winter. If you keep the winter temperatures high enough (20°C or more), the plant will keep its green leaves, but will drop most of them them when kept cool (15°C). It can grow to a height of six metres, producing a whitish bark which contrast with the green leaves.
The flowers are produced after about five years from seed; the flowers are yellow as with most Cucurbitaceae and unisexual and monoecious (growing on the same plant). The fruit is orange, but fairly small and mainly eaten by the sheep and goats on the island. Traditionally, it is also used for medicine.
Propagation is mainly from seed, but a few exeperiments that I have done prove that it is possible to propagate the plant from cuttings. One needs tip-cuttings put it a high humidity propagation unit, so that the cuttings will not dry out. I do not yet know, however, if the plants will form a caudex if grown from cuttings. Experiments are ongoing.

For a more complete description of this interesting plant, see here.

Dendrosicyos socotrana

Dendrosicyos socotrana


 

This perennial climber comes originally from South-America, but has now spread over most of the the warmer parts of the world. It is also known as Madeira or Potato vine. Growers in Europe have this as a collector’s plant in their greenhouse, whereas in the warmer parts of the world, they are trying to get rid of it. In some countries is has even become an invasive weed that is difficult to eradicate, because it is almost impossible to get rid of all the small tubercles. When you dig up the plant, the small tubercles that have formed on the stems fall off very easily.
Cutting the stems and leaving the branches lying around does not help to kill the plant, because there is enough energy left in the stems to produce the small tubers. If you really want to get rid off the plant, you need to burn the stems (make sure you gather up all the tubercles that have fallen off) or poison the plant with Glyphosate. You need to do the latter by scraping the bark and putting the poison on the wound so it will be taken into the plant. A bit harsh, but it is the only way unless you happen to live in a country where the temperatures fall below zero, because they cannot take any frost.
Anredera can grow to up to 9 metres long and has bright green heart-shaped leaves. In the autumn, it produces large numbers of small fragrant flowers in racemes. It can grow in semi-shade or full sun and can take a lot of drought. It is propagated mostly by tubercles, rarely by seed. Because it is such a rampant grower, it can be cut back almost to the tuber and it will come back and flower the following year – an ideal beginners plant.

Anredera cordifolia

Anredera cordifolia


 
Anredera cordifolia raceme

Anredera cordifolia raceme


 
Anredera cordifolia tubercle

Anredera cordifolia tubercle

Biophytum sensitivum comes from Africa and India and grows to about 20cm high in a rosette which gives the impression of a small palm tree. As with other similar plants, such as the Maranta, the leaves shut at night. It does not require special soil, but keep it moist at all times. Most people know the plant Mimosa pudica, the sensitive plant, but another plant, less well-known, is the Biophytum sensitivum which also has similar properties of being able to close up its leaves for protection. However, in this case, the leaves are folded downwards whereas on the Mimosa they are folded upwards. The only pests that may attack the plant are fungus gnats whose larvae gnaw away at the base of the stem. In the wild, other plant-eating insects will try to feed on this plant, but to combat this, the plant folds its leaves and the insect falls off. As the leaves also contain the poison oxalate, it is not clear why the plant has this additional leaf-folding protection.

The Biophytum was first described in 1753 as Oxalis sensitivum, possibly because Oxalis and Biophytum shoot out their seeds in similar ways. This is a sure way of reproducing itself as at least some of seeds fall onto good soil and will germinate quite quickly. Watch out for this phenomenon in your greenhouse, as you may end up with Biophytums all over the place. This only happens if you keep the temperatures above 16° C. at all times, as they do not like cold. It is an ideal plant for terrariums with their high humidity and low light, because that imitates their natural conditions. It is an annual, but it will live for more than one year. Make certain to save some seed while it is available, because the plant may suddenly die and you would be left with nothing. The flowers do not have to be cross-polinated, so one plant is enough to produce seed. When the seedpod is ripe, it will open up into a star-like structure in which you can clearly see the seeds. It opens up in the morning and by the afternoon, all the seeds have sprung, so make sure to collect them in time.

Biophytum sensitivum

Biophytum sensitivum


Biophytum sensitivum seed pod

Biophytum sensitivum seed pod