Urginea maritima (sea squill, medicinal squill) is a common plant that stands out in the landscape. It blooms at the end of the summer and in the autumn. It has a unique phenology and shape: in its bulb, its leaves, its inflorescence and its (toxic) natural materials.
The annual course of the sea squill's life is divided into two separate seasons: in November it grows leaves and the vegetative stage of the plant's life begins, which continues throughout the winter and early spring. In April the leaves wilt, and all above-ground parts of the plant die. At the end of the summer (August-September) the inflorescence stalk begins to grow, and the generative stage begins for several weeks, after which the sea squill again has no live above-ground parts.
The inflorescence stalk is tall (70 to 180 cm), single and not branched, with dozens of flowers (50 to 250) arranged along its length on short pedicels in an elongated spike. Blooming begins from the bottom, and every day another group of about 30 flowers opens above the previous ones, and the flowers that opened the day before wilt.
The single flower is small, with a diameter of approximately 10 mm, and its structure is typical for the Liliaceaeae family: 6 tepals - the 3 outer ones may originate from the sepals and the 3 inner ones originate from the petals, but all belong to the corolla. They all look alike, so we will call them tepals, i.e. petals and/or sepals. These leaves are white on the inside, whereas on the outside there is a longitudinal green band that passes through their center. They reflect ultraviolet radiation.
There are 6 stamens inside the tepals and further inside is a triangular ovary. The sea squill is a typical representative of a group of 25 geophytes in Israel, which bloom in autumn, and were therefore given the name "the squill group". Blooming in autumn has advantages as well as disadvantages: Its advantage is in that most other flowers do not bloom in this season and the squill thus avoids competition over the pollinators. The disadvantage is that most flowers know why they prefer to bloom in the spring, when pollinating insects are numerous, whereas fewer are active in autumn. Perhaps this is why the sea squill did not evolve refined adaptation to a specific pollinator.
The flower is filled with plenty of nectar and it is wide open, and has no mechanisms for preventing nectar robbery. It therefore visited by a large variety of insects, and is open to all, including insects which are not effective as pollinators at all, such as wasps and flies that can be regarded as "nectar robbers", which do not benefit the flower.
In a study performed by Reuven Dukas and Amotz Dafni it was found that the sea squill employs the principle of "hedging its bets" in pollination. In addition to pollination by insects, it employs wind pollination to some extent, as well as some self-pollination, even though a certain extent of self-incompatibility was found. Among the different insects that were found on sea squill flowers, the important pollinators are the honey bees, the European paper wasp (Polistes dominula), the Oriental hornet (Vespa orientalis), and perhaps also the cotton bollworm (Helicoverpa armigera) (a type of moth). Other visitors are more appropriately called "nectar robbers", and are not beneficial for pollination. These include ants, flies (the housefly, the flesh fly) and single small bees that are unable to pollinate due to their small size, because they do not reach the stigma when drinking nectar or collecting pollen.
The flower opens at 01:00 AM, and remains open for approximately 18 hours, until 07:00 PM. Even though it opens at night, and its white color is compatible with pollination by nocturnal insects, only few such insects have been observed on the flowers. Immediately upon opening of the flower, its pollen ripens, and nectar is secreted from 3 nectaries that are located in the ovary wall. The nectar is produced only until 05:00 AM, and as time goes by the nectar thickens due to evaporation.
The bulb is by far the largest of all bulbs of wild flowers in Israel. Its diameter may reach 25 cm. The bulb is a group of underground leaf bases which store food and swell. The sea squill bulb is composed of imbricate leaf bases, i.e. they only partially cover each other, and it is therefore considered to be a scaly bulb. Every year the outer scales empty and become scarious shells, whereas the new leaf bases that develop in the center of the bulb store food and are added onto the bulb from the inside.
A bulb is essentially a store of nutrients. Such a store has many advantages, but also a disadvantage - it attaracts animals to enjoy the food it contains, and eat it, and an ongoing battle takes place between the plant and the animals that eat it. In order to protect the bulb against the animals, the plant has buried the food store in the soil, as did others in its family, as well as the other geophytes in several families. However, there are many animals, such as the boar and the deer, the mole rat, the porcupine and other rodents, which are able to dig in the soil in search of food. The sea squill therefore evolved the ability to produce a repelling toxin, which harms animals but not plants, and disperses it in its tissues, in the bulb and in the leaves. The toxin contains cardiac glycosides and skin irritants.
However, there are animals that are able to pass the food through their guts and absorb the nutrients without absorbing the toxins into their tissues. What did the sea squill do? It also evolved tiny needles in its tissues, which are composed of calcium oxalate. These needles damage the intestinal wall and blood vessels in this wall, and the toxin thus penetrates into the blood. It seems that in this war, the sea squill is usually the victor, but in some cases it is still eaten.
In the Middle Ages the toxin was used as a cardiac stimulant, and hanging the bulb of a sea squill on the doorway was regarded as an attribute for fertility in ancient Egypt and Greece.
A few parallel roots (fibrous root system) descend from the bulb downwards, and leaves and the inflorescence stalk ascend upwards. Some claim erroneously that even if the bulb is uprooted, and only the roots remain, they can rehabilitate the plant and grow a new bulb in the same place. This explains the tradition of the Sages of Blessed Memory that the sea squill is suitable for marking the boundaries between the plots of neighboring farmers, and that Joshua marked the borders of the Land of Israel with sea squills. A plant called hatzuv is mentioned a few times in the Rabbinic literature, but it is not always clear whether it refers to this plant, and which of its properties it tries to describe.
The sea squill bulb does not tend to split, but if it is split by an external factor, a human or some other animal, the bulb parts can reproduce vegetatively.
An experiment was performed in which a sea squill bulb was kept outside the soil, and the food and water store that it contained was enough to enable the plant to bloom, albeit modestly, for 10 years.
Due to the food and water store in its huge bulb, the sea squill can afford to put out leaves even before the first rain, and can thus carry out photosynthesis and produce new food without competition from other plants. Indeed, in November the green sea squill leaves are prominent as fresh islands in a landscape of wilted plants. The leaves are fleshy-leathery, broad ensiform. They are covered by a layer of wax that affords them a bluish hue. Raindrops on sea squill leaves, which this layer emphasizes, are known among nature photographers as an attraction. All leaf eaters will of course pounce on this sole greenery. Here the toxin saves the sea squill leaves from those who would eat them, although once in a while some deer or rabbit or hare overcome their fear of the toxin, and we will be able to see some sea squill leaves with their tip bitten off. Perhaps when the leaves just begin to sprout, when only the tip protrudes out of the ground, the toxicity is not so high? And how does the animal know this?
There is no "absolute solution" and there are animals that eat the sea squill in spite of its toxicity. These include snails that eat the margins of the leaves and a mirid bug (Capsodes infuscatus) which sticks its thin trunk into the leaf tissue and sucks it, perhaps avoiding harming the toxin containing cells.
At the end of spring, after the leaves have wilted, they no longer contain toxin, and young cattle chew the dry leaves enthusiastically, or perhaps they enjoy the rustle, as they enthusiastically chew paper. At this stage there is no harm to the plant, the one benefits and the other does not suffer.
A careful look at the exact location where the inflorescence stalk begins relative to the position of the (wilted) leaves indicates that the flowering belongs to the leaves that wilted, and not to those about to sprout. Thus, flowering does not begin the annual life cycle, but rather ends it. The sea squill is not an early bloomer, but rather is a late bloomer relative to the leaves.
The fruit of the sea squill has a triangular cross section, and contains seeds enveloped with a spongy-corky lightweight cover, which is surrounded by a water-impermeable membrane. It appears as if the seeds are intended to be dispersed by floating on water (and indeed, the German name of the plant is "sea onion"). However, the origin of the cover and it purpose are not clear. In any case it is clear that the seeds effectively fulfill their purpose of increasing the sea squill population.
The distribution of the sea squill in Israel is broad, and it is very common in the entire Mediterranean region, on the mountains and the plains. It also grows in the desert, where it is rarer.
The species is common in the countries surrounding the Mediterranean Sea. The genus contains 100 species, whose distribution ranges from the Mediterranean region southwards to the desert and even to the margins of the tropical region. Only one additional species, Urginea undulata, which is more modest and rarer, grows in Israel.
Written by Mike Livne
