Plant Genus: Sarracenia

Common Name: The North America Pitcher Plant
 
Number of Species: 8
 
Places found naturally: Canada & The U.S.A.

Sarracenia (sarraceniaceae)

The North American Pitcher Plant or Sarracenia are native to the south eastern coastal areas of North America with the exception of one species (S. purpurea ssp purpurea) that grows in the northern regions of the USA and Canada reaching as far north as Newfoundland where it is the province’s national flower!

Most species form tall upright pitchers that look like organ pipes and they are difficult to miss when seen in any collection! Other species form recumbent pitchers that are more ground hugging. For the purposes of simplicity the species will be divided into those that collect rainwater and those that do not.

Most Sarracenia species form tall upright pitchers. Colouration differs according to the species and in some instances even differs among the species! All share the characteristic of having a lid that shelters the tube from rainwater. The morphology of the pitchers is similar among all species. Nectar is produced by all parts of the pitcher but the greatest amounts of nectar is produced around the rim of the pitcher and along the column that forms the inside part of the lid. The plant advertises the presence of the nectar by the colouration of the pitcher. Red line in particular act as nectar guides to visiting insects directing them to richer supplies of nectar. In this respect the pitchers can be considered to be imitating flowers!

As the victims move towards the richest supplies of nectar they inevitable move to the rim of the pitcher. Inside the pitcher the surface rapidly changes from one with a firm foothold to a very slippery one with no grip whatsoever. As the insect moves down it almost inevitably loses its foothold and falls inside the pitcher. From observations this can happen to a flying insect several times and it will still be able to fly out. However, the plant has another secret weapon up its metaphorical sleeve! The nectar also contains a mild narcotic that reduces the reaction times of the insect. Once it had fed enough the insect loses its footing for a final time and this time plunges into the depths of the pitcher.

Inside the pitcher the smooth walled section changes to one with downward pointing hairs. The hairs server two purposes. First in combination with the smooth section, the walls of the pitcher make it virtually impossible for any insect to crawl out. Second and more importantly, the downward pointing hairs mean travel down the pitcher is much easier for the trapped victim than it is to move upwards. In its attempts to struggle the insect inevitably moves down the pitcher as far as it can. This has the rather convenient result that the trapped insects effectively compact themselves making the pitcher capable of containing a greater quantity of insects.

Inside the pitcher glands in the inner wall secrete a digestive enzyme which breaks down the soft tissues of the insect into a liquid that is readily absorbed by the pitcher walls.

Examples of this type of pitcher are S. alata, S. flava and S. leucophylla.

Two other species of Sarracenia are sufficiently specialised to be dealt with separately.

S. psittacina forms small prostrate pitchers that grow close to the ground. In habitat the pitchers are usually completely covered with grasses and it is likely that this species specialises in trapping crawling ground and soil borne insects. The pitchers are closed at the end except for a small opening near to the end of the pitcher. This opening is shaped much like a lobster pot making it extremely easy for the insect to find it’s way in but much more difficult to find it’s way out. The inside of the pitcher is lit by the white window-like areas (fenestrations) that cover most of the pitcher. These appear to serve two purposes. First the fenestrations light up the inside of the chamber. An insect is far more likely to go into a well lit area than once that is relatively dark. Once inside, the fenestrations act to camouflage the entrance to the pitcher. As with most other Sarracenia nectar is produced by the pitchers to attract the insect prey.

Once inside the insects eventually find their way to the lower reaches of the pitcher. Here the same downward pointing hairs are present which coax the insect further down the tube. The hairs have a far more important job in this species in preventing the insect’s return, gravity having a less important role. Once inside the pitcher digestion occurs as with the other species.

The other species that differs radically is S. purpurea. Largely there are two sub-species, one found in the southern USA, the other occurring in the northern parts of the continent.

This species differs in both the form of its pitchers and the way it traps and digests its prey. The pitchers are usually squat ground hugging and most importantly, the pitcher ends are open to rain and in fact actually form receptacles that collect rainwater. Insects are still attracted to the pitcher by nectar as with other Sarracenia species but an additional attraction is sunlight reflected in the water contained in the pitcher. This is a strong attraction for all sorts of insects.

Once the insects land in the water there is little or no prospect of escape! The water contains a wetting agent that causes the insect to sink rapidly and drown almost as quickly. The plant produces no digestive enzymes but instead relies on naturally present bacteria to break down the soft tissues of the insects, the nutrients being eventually absorbed by the cell walls of the pitcher.

The plant is particularly common in the extreme north of the continent and this almost certainly due to certain adaptive features that suit the climate. First, because the pitchers sit on the ground they are virtually immune to wind damage. The toughness of the pitchers and the fact that they are well insulated from cold winter winds means that the pitchers are far more likely to survive winter conditions intact. This gives the plant a huge evolutionary advantage. Any trapped insects in the water are frozen when winter arrives. This effectively holds the insects, nutrients and all in deep freeze through the entire winter. When the thaw arrives in spring the pitcher is ready to go and can not only supply nutrients from the insects trapped from the previous year but it can even trap new insects right away. This must give the pitchers a significant advantage in an area where the summers can be very short indeed because while the plant is producing new pitchers, the ones from the previous year are still productive.

Contrary to popular opinion no parts of the pitcher plant is able to move – especially the lids!

Cultivation: This is very straightforward. Most species can be grown outside in the UK, particularly so in the southern counties. However, an unheated greenhouse will significantly improve growth rates and pitcher colouration. The genus can be considered totally hardy and so no heating is required.

Watering is by the tray method with watering reduced during the winter months. The growing season is roughly from April through to September with flowers produced in the spring. It is important that these plants receive no calcium in either their growing medium or the water as this is the most effective poison known to man! The best soil mix is two parts sphagnum moss peat to one part perlite. Some peat free mixes have also been used with considerable success.