The Mishna (12a) taught that not all types of natural growth can be used as skhakh – roofing – for the sukka. Straw or branches that are tied into bundles are examples of growth that cannot be used unless they are untied.
The Gemara on our daf quotes a baraita which says that thorny plants can be used for skhakh, even though they grow twisted together and might appear to be bundles. As we will see, growing as a bundle will not be an impediment for use as skhakh, although there might be other problems with such plants.
Rav Hanan bar Rava teaches that the thorny plants hizmei and higei are both appropriate for use as skhakh on Sukkot. Abaye disagrees with the ruling regarding higei, explaining that its leaves fall off easily and will disturb the people eating in the sukka, likely inducing them to leave.
Hizmei can be identified with Ononis antiquorum L. of the Papilinaceae family. It is a thorny plant that grows to about 75cm (2.5ft), which is found growing wild in fields and valleys.
The scientific name for Higei is Alhagi maurorum Medik. It, too, is a thorny plant with smooth, non-serrated leaves. Ordinarily it grows to a height of 30cm (1ft), although it occasionally grows as high as one meter (3ft).
Another plant discussed on our daf is the eizov. The Sages did not come to a clear conclusion about the identification of this plant, which is mentioned not only in the Talmud, but in the Torah, as well (see, for example, Bamidbar 19:6 where it is translated as hyssop). From the descriptions given it appears that the eizov is likely Majorana syriaca, a fragrant shrub that rises to a height of about 50-100cm. The plant is commonly found throughout Israel and in neighboring countries. Its dried leaves are a primary ingredient in the popular local spice mixture za’atar.