Marsh Meanderings III. Ice (a)

Posted by:

2 December 2019

Ice – Information

Ice Flowers (b)

There’s much to marvel about as low temperature changes the state of water from liquid to solid.  Ice is amazing!  My purpose here is to encourage you to look more closely at the ice that appears at the edges of marsh waterways and with enough cold, the entirety of Spring Lake as well as the various nearby marsh and tidal areas.  Look, too, at puddles that form when snow melts and nights are cold.  Regardless of where you look, timing is key.  Get out before the sun warms the ground and causes the ice to melt.

In my experience, the best time to see tidal ice is when high tide occurs between 2-4 a.m.  Ice likely forms during slack tide, the time before the tide changes from incoming to ebbing and there is the least water movement.  Then when the tide ebbs, the ice is gently deposited on the marsh surface and is there when the sun is up and you’re there to see it. (This is my suggestion regarding tidal ice formation, but I’ve not done a systematic study, and haven’t run across any information about this).  Check the marsh website for the link to current tides.

On any given day ‘good’ ice, ice that has photographic possibilities, can be challenging to find.  There are no guarantees.  It depends on, most obviously, low temperatures, available water, and good light.  These conditions may be quite transitory.  Frost and thin ice can be changed back to liquid water by midmorning.  Snow, even a dusting, can cover details and fuse with ice destroying interesting features. Yet interesting ice patterns can be found along stream edges even when the ground is snow covered.  Following rain or snowmelt, water can accumulate and freeze in shallow puddles.  High winds can create waves that reach tree branches, transforming them, but once freeze-up occurs, splash ice no longer forms.

Part of the magic is finding what nature has unpredictably arranged, and adding to the allure are sounds of ice cracking and moaning, and the challenge of avoiding missteps.

Tidal Ice – with unusual crystals on the bottom.

I first really saw ice on a Christmas bird count on Duck Island near the Delaware River on January 1, 1995; that was my first three-dimensional ice.  Since then, most ice sightings have been within 20 miles of home – our patio, Plainsboro Preserve, the Millstone floodplain near Griggstown, and the Abbott Marshlands, including the banks of the Delaware River, and Crosswicks and Watson’s creeks.  I have ventured farther afield with a few forays along the Wickecheoke Creek near Stockton, NJ, the cliffs near Frenchtown, NJ and Easton, PA, and streams in the Pinelands.

ICE — At the Interface of Life and Art

The molecular composition of water, two atoms of hydrogen and one of oxygen (H2O), is known to virtually everyone.  Key to its properties that make life as we know it possible is the bonding between hydrogen and oxygen atoms. While the actual molecular arrangement of liquid water is unknown to scientists, that of ice is.

The special properties of water that affect the Earth’s biosphere include:

–water is transparent to light, allowing light to penetrate, for example, our eye for vision and plant cells for photosynthesis.

–a great amount of heat is involved in changing state – 80 calories per gram of water must be gained or lost for the transition from ice to / from liquid at 32ºF (0ºC) and 540 calories from liquid to / from steam at 212ºF (100ºC).  This ability to absorb and give up energy is important in moderating the Earth’s temperature.

-the greatest density of water is at 39ºF (4ºC); as water cools below that point it expands and floats.  Freezing of a lake, therefore, is a top down process, permitting organisms to survive at the unfrozen bottom.

What happens to water to create ice?

Loss of heat energy with cooling results in an increase in the number of hydrogen bonds between molecules.  In water at 32ºF only 15% of molecules will be bonded together, while in ice at 32ºF, 100% will be. As the temperature falls below 32ºF, the bonds between the hydrogen atoms of one molecule and the oxygen of another molecules become ‘stronger’, locking molecules together.  In ice, the attraction of molecules causes a lattice to form.

To begin the freezing process, water needs to collect around a nucleus to ‘learn how’ to position its molecules in the crystal lattice.  The nucleating material can be a foreign particle, a bit of dust, vegetation, or bacteria, or a salt grain.  These cause orderliness to occur amid the randomness of molecules found in liquid.

As water freezes, crystals form.  They may take the form of needles or plates and both may occur at the same time.  Crystals one to two feet long and three feet wide (!) have been observed in lakes.

Effects of ice on organisms


The damaging effect on tissue is the rupture of cell organelles and membranes by enlarging ice crystals or by the unwinding of enzymes that then lose their ability to catalyze metabolic reactions.

Ice in soil, e.g., needle ice, can dislodge seedlings and tear plants apart.


For organisms in bodies of water, ice may insulate, preventing too low temperatures from developing.

Among plants and animals there are tolerators and avoiders. Avoiders may migrate (vertically into the soil or to more moderate climates) or, in the case of plants, produce seeds with low moisture content that are not affected by low winter temperatures.  Tolerators may change cell contents, e.g, by increasing the amount of sugars and other materials that act like antifreeze, or by producing nucleating proteins that reduce the size of ice crystals that develop.

Kinds of ice

Ice may be called, for example, fraizel slush, candle ice, needle ice, segregation ice, or splash ice.  Each has its own characteristics and method of formation. Eskimos have more than a dozen words for ice.

Spring Lake Bubbles – Bubbles are likely of methane gas produced by anaerobic methanogenic bacteria that live in the lake bottom sediments

Ice as art

If water freezes slowly, ice is clear, the air having had time to diffuse away into the surrounding water.  If it freezes quickly, air bubbles can be trapped.  Ice with few bubbles is clear; that with many is white.  The patterns that develop in ice are likely related to what triggers ice formation (air, impurity within the water, a twig), but under apparently identical conditions of temperature, air pressure, environment, etc., many diverse types of ice crystals can form and grow (witness snowflakes) at the same time in a given body of water.

Water can also freeze when it splashes onto trees, rocks, or other cold objects along the sides of ponds, lakes, or waterfalls or when it drips off a roof.  It can condense out of the air to create frost feathers and lace on windows, or roses on the surface of ice.

Splash ice – edge of  Delaware River.

Pancake ice, Delaware River.

 Ice jam, Delaware River at Trenton Boat Launch

The beauty of ice is related to random and varied crystal forms, to bubbles, and to the way light is dispersed, reflected, and transmitted through it.

Suggested Reading / References:

Ball, P.  2001.  Life’s Matrix: A Biography of Water.  University of California Press, Berkeley.

Gosell, M.  2005.  Ice: The Nature, the History, and the Uses of an Astonishing Substance.   Alfred A. Knopf, New York.

Pielou, E.C. 1998.  Fresh Water, University of Chicago Press, Chicago.

The web:  search for ‘ice forms’. reports (from Physics Mar 24, 06) discovery of two new ice forms at –160ºC.

All photographs are the property of the photographer, MA Leck; please address questions to:

Exploring Ice Flowers


Marsh Meanderings II. Jewelweed

Posted by:

22 August 2019

Jewelweed flower with honey bee.

Jewelweed flower with honey bee.

Jewelweed, a common Abbott Marshlands plant, is found in marsh and swamp as well as moist upland locations. In the tidal marsh it can reach 6 feet in length; in other places it may be only a few inches tall when it flowers. In late summer into September in moist areas, its orange flowers with red spots can be conspicuous. Look for them along stream and pond edges and wet road sides. Plants are killed by frost.

This is a species with many names, each tells a little about it:

Common names:
Jewelweed & Silverleaf – leaves held under water appear silver because of a thin film of air trapped on the surface by microscopic hairs. Leaves are not wetable; water beads on surfaces as if they’re covered with oil. This is especially obvious on the undersides of leaves. The adaptive value of this waterproofing is not known.

Touch-me-not & Snapweed -refers to the explosive ripe fruits. Ask an unsuspecting person to ‘pick’ seeds from a mature fruit!

Spotted Jewelweed & Spotted Touch-me-not – flowers have red spots on petals.

Lady’s Eardrops – refers to the shape of the flower.


Scientific names:
Impatiens – refers to the impatient, explosive nature of seedpods, which can disperse seeds two feet or more away from the parent plant.

Impatiens capensis, actually a native North American species, was mistakenly thought by Nicolass Meerburgh to be native to the Cape of Good Hope, in southern Africa. Africa is home to many Impatiens species, but not this one or Impatiens pallida that can also be found in the Abbott Marshlands, especially along Lamberton Road on Duck Island.

The name Impatiens biflora, found in some older reference books, is superseded by I. capensis. The ‘biflora’ refers to the two types of flowers a plant can produce. These are showy orange flowers with an elongated spur, often with red spots, and small inconspicuous flowers. The showy flowers require a pollinator, while the small ones are self-pollinated.

The technical name for the large, showy cross-pollinated flowers is ‘chasmogamous’.

The other type is small, green, and inconspicuous; these never open, self-pollinate, and are called ‘cleistogamous’ flowers.

Top flower is in the male phase; bottom is in the female phase

The showy flower has a landing platform for insects formed by the two lateral petals, and a tubular nectar spur, which is a sepal. The showy flowers, while having both male and female parts, assure that cross-pollination occurs by an extraordinary process. When a showy flower opens, it is functionally male because the anthers are united around the stigma and form a covering over it. After the male phase, which lasts for ~ 24 hours, the anther cap falls off exposing the female stigma. The flower is in the female phase for ~5 hours. It is during the female phase that pollination, leading to seed production, can happen. During the male phase, pollen is picked up when a visiting insect or hummingbird is dusted with pollen from the anthers. The pollen is carried to a flower on another plant that’s in the female phase. Cross-pollination appears essential for the production of seeds in showy flowers.

Female phase, with dislodged anther cap resting on the landing platform.

The anther cap is dislodged by elongation of the ovary. Nectar is produced in the spur and is about 40% sugar and contains 25 amino acids. The mix of amino acids contains all but one of the 16 considered essential for insect nutrition.

How do pollinators locate flowers? Insects can ‘see’ ultraviolet light; and reflection patterns show that the spur, the inner surface of the petals, and the anthers reflect UV light. The principal insect visitors in a Delaware study were of four types: pollinators (10 species), primary nectar thieves (6 species), and secondary thieves (21 species; some of these take nectar from a hole made by a primary thief, and others are small enough to pass under the anther cap or stigma while taking nectar). The most abundant pollinators were bees (Bombus vagans, B. impatiens, Apis mellifera) and the yellow jacket (Vespula maculifrons). The only bird visitor was the Ruby-throated Hummingbird, which is attracted to flowers by color and sees the red dots on the petals.

Two tiny cleistogamous flowers.

Compared with the showy chasmogamous flowers, the inconspicuous cleistogamous flowers, are reduced in size, as is the number of pollen grains. The pollen apparently begins to germinate while on the anther, and because the parts are so close together, the pollen tube grows and penetrates the stigma. Fruits produced by both types of flowers are similar, but those from the cleistogamous flowers are usually smaller and contain fewer, smaller seeds.

Cleistogamous fruits (note arrows).

So, why does this species produce small self-pollinating flowers? The smaller flowers are about a third to half as ‘expensive’ for a plant to produce. Therefore, even if resources are limited, plants in stressful habitats can still produce seeds for the next year. Resource-limited habitats may have low light or are places that tend to dry out during the summer. Most Jewelweed populations produce both types of flowers, but those that produce only small cleistogamous flowers retain the ability to produce showy flowers if they’re grown where conditions are optimal.

Jewelweed is an annual species, dependent on seeds for survival from one year to the next. There are virtually no seeds remaining in the soil after spring germination.

It was quite a circuitous route, but Jewelweed is the plant that led me to the Abbott Marshlands. I first noticed seedlings on the bottom of a stream in western Massachusetts in April many years ago while visiting my folks. This led me to wonder about O2 requirements for germination. Several years later I began my first germination study, which involved many treatments, including +/- light, several temperatures, scarification (nicking the seed coat), and several concentrations of gibberellic acid (a growth hormone). The oxygen concentrations came later. I had collected seeds in autumn, stored them in a glass jar, and placed them on the lab bench until the following spring semester was finished. Of hundreds of seeds, nary a one germinated, while those that I’d left with my mom in her refrigerator and that she watered when she remembered, germinated! That germination failure put me on notice; after that I set up germination studies soon after harvest or provided optimal storage conditions: seeds of this facultative wetland species cannot be dried.

Subsequent germination tests showed that seeds require oxygen for germination and, in fact, are killed if subjected to anaerobic conditions for a period of time. This is easy to test: place seeds into a small jar and, because seeds float, make a small sac of netting (a piece of an old nylon works), add a small clean stone or marble to weigh it down, fill jar to the brim with water, close the lid tightly eliminating bubbles, place it in your ‘frig’; this has little available oxygen. Compare what happens with a second set of seeds that receives oxygen: set these seeds on a piece of very moist paper towel in a small jar, loosely cover the jar and remember to add water to the paper from time to time. After about 4 months remove the lid of the first jar and dump off most of the water; check the second jar. The seeds in the anaerobic jar will not have germinated in contrast to those in the second jar with oxygen.


Jewelweed seeds have some apparent peculiarities:

Jewelweed seeds: brown with seed coat intact; others with seed coat removed showing the blue color of the seed itself.

Below the brown seed coat, there is a turquoise blue layer. Reports indicate that white-footed mice feeding on Jewelweed seeds have blue tummies. (I personally have not seen this, but Charlie Leck has).

Seeds can float for more than 2 months. Evidence for this ability to float, can be seen where seeds have drifted and collect along the edge of a log where they germinate in dense groups. (See photo).

Jewelweed seedlings from floating seeds caught by marsh debris.

Seed dispersal is also from the explosive fruits.  Studies have shown that energy storage is greater than of elastin (elastic protein in connective tissue) and spring steel. Video studies have documented that the process of dispersal is very rapid.

Fig. 1 Sequential video tracings of an I. capensis seedpod before and during dehiscence. The numbers how the time in milliseconds fro the start of dehiscence. (from Hayashi et al. 2009)

Seeds need to experience moist cold storage, called stratification, for 3-4 months. This allows chemical changes necessary for germination even in a refrigerator. The process can be halted by storing just at freezing and then germination can be timed to coincide with a desired planting time. A test showed that after stratification at 41 F (5C), germination was more than 85%, but at 50 F (10 C) it was only 25%.

Seeds do not tolerate prolonged inundation and low oxygen levels; they die. My observation of seedlings in a stream was probably a fluke; the seeds may have germinated along the stream edge and then seedlings fell into the water.

Seeds do not tolerate drying.

Light is not required for germination.

Seeds from the Abbott Marshlands tidal marsh were 4.2 times larger than those from a low light environment (in a study that compared eight populations from central NJ); seedlings were also larger. The large size of seedlings is an advantage in a habitat where growth is rapid.

Germinating seeds produce a ring of roots rather than one main root; this feature, noted in many mudflat species, provides anchorage and stability in a ‘liquid’ substrate and allows root development at the aerobic mud surface. The tips of the roots are red; the adaptive value of this is not known.

Seedlings from a cache of seeds stored by a white-footed mouse.

Seeds are edible and reportedly taste like walnuts. Groups of seedlings can be found in the spring where seeds collected by mice were cached, and then left uneaten.


Jewelweed Uses:
Jewelweed stems can be crushed and sap used as an antidote for poison ivy, insect bites, and nettle stings. As noted, seeds can be eaten; the showy uncooked flowers can be eaten in salads or cooked in stir-fry. Some websites indicate that stems and leaves can be eaten if boiled for 15-20 minutes with two changes of water.  Frankly, I’m leery of plants that need to be boiled and water changed twice to remove high amounts of calcium oxalate and selenium!

Photographer Lucas Foglia reports that some people use flowers for making soap (pers. communication, Aug. 2019).



Eastman, J. & A. Hansen (Illustrator). 1995. The Book of Swamp and Bog. Trees, Shrubs, and Wildflowers of Eastern Freshwater Wetlands. Stackpole Books. Mechanicsburg, PA.

Hayashi, M, KL Feilich, and DJ Ellerby. 2009,  The mechanics of explosive seed dispersal in orange jewelweed Impatiens capensis). Journal of Experimental Botany 60: 2045-2053,

Leck, MA. 1979. Germination behavior of Impatiens capensis Meerb. (Balsaminaceae). Bartonia 46: 1-14.

Rust, RW. 1977. Pollination in Impatiens capensis and Impatiens pallida (Balsaminaceae). Bulletin of the Torrey Botanical Club 104: 361- 367.

RL Simpson, MA Leck, VT Parker. 1985. The comparative ecology of Impatiens capensis Meerb. (Balsaminaceae) in central New Jersey. Bulletin of the Torrey Botanical Club 112:295-311.

Mary Allessio Leck
August 22, 2019


Marsh Meandering  I.  Wild Rice
7 June 2019

A walk along the D&R Canal Towpath trail at low tide revealed small sandbar islands that are now well vegetated with wild rice (Zizania aquatica) seedlings already more than a foot tall.  It’s the only grass growing in that habitat.

This annual, an obligate wetland species, can grow to more than 10 feet by the end of the growing season. After flowering in August and setting seed, it will die. Its seeds are a favored food of many birds including black birds, such as Red-winged Blackbirds and Grackles, and migrant ducks.

Interestingly, there is no evidence of use of Wild Rice by Native Americans in the Delaware River Valley although northern tribes used it extensively.  Much of what’s sold commercially is grown in Minnesota and California.

Arrow shows Wild Rice seed from which the seedling at the left grew. The white root-like structure is the hypocoty (Greenhouse) (c MA Leck)

The slender seeds are more than one inch long with a needle-like extension, called an awn, making up part of its length. From this seed first emerges a seed structure, known as the hypocotyl, and then the shoot. Roots take a bit more time. As human food, they are gluten free, and provide fiber and various nutrients.

Seeds cannot be dried. Early colonists were not successful in bringing them to Kew Gardens in England until it was discovered that seeds needed to be stored in water.

Wild Rice can be found in wetlands throughout the Abbott Marshlands. Young plants can tolerate being inundated. Look for them in mucky, muddy places, the bottoms of small tidal streams, shallow ponds, and in the abandoned canal along the towpath trail where in spring there are often dense grouping of light-green grass plants.

Wild Rice seedlings

Wild Rice seedlings (May 25) in a tidal channel at low tide.

When Wild Rice flowers, male flowers are below the female ones. The yellow male flowers make the plants conspicuous.  Flowering is from late July to September.


Wild Rice

Wild Rice inflorescence. Female flowers are at the top, male flowers below. (Aug. 26).

Wild Rice along Crosswicks Creek (Aug. 26).

This is one of the food plants for caterpillars of the Broad-winged Skipper. Adults (~0.8 inch) obtain nectar from dogbane, swamp milkweed, pickerelweed, thistles, etc.

Broad-winged Skipper (Wikipedia)

Broad-winged Skipper (Wikipedia)

Botanical facts: The Wild Rice species found in the marsh is Zizania aquatica a member of the grass family (Poaceae) like corn or your lawn grass. There are three other Zizania species: Z. palustris is found in northern areas (Minnesota, Wisconsin, Canada) and Z. texana, a perennial species now endangered, occurs in central Texas; Z. latifolia, Manchurian Wild Rice, now rare in nature is native to Asia, where it is cultivated for its stems that are eaten as a vegetable.

Like corn, Wild Rice is monoecious, with both male and female flowers on the same plant, but in Wild Rice, the male flowers, where pollen is produced, are located below female ones.  Male flowers are typically yellow, but may sometimes are reddish.

Because of the economic value of wild rice for human consumption, much research has been focused on learning how to germinate seeds. Early work showed that seed dormancy can be broken by prolonged cold treatment (e.g., 3-6 mo at 1-3 C; 21-37 F) at low oxygen levels, as would occur if submersed in water or in mud at the bottom of a tidal stream. (Although many factors can influence the actual amount of oxygen in water such as temperature and wind, the content of air is 20%, while that of water is 1%, which is why people drown).

Seeds can remain dormant for more than a year. This can account for field observations that some years in some locations in the Abbott Marshlands there may be few or no Wild Rice plants. Long seed dormancy poses problems for plant breeders who desire multiple crops per year, and for growers who wish to change varieties in established fields.  However, freshly harvested seed can be germinated, if first dehulled by scraping and stored 1-4 weeks at 1.5 C (35 F).

Red-winged Blackbird feeding on Wild Rice (Sept., c MA Leck).



Warren Libensperger showing height of Wild Rice (Sept. 1).

For tides, consult the marsh website ( -Tides) or local newspapers.

Background and for use of Wild Rice by Native Americans and other background see

For use in the Delaware River Valley:
Messner, Timothy. 2011, Acorns and Bitter Roots: Starch Grain Research in the Prehistoric Eastern Woodlands. University of Alabama Press, Tuscaloosa. (p. 21).

Also: Personal Communication, Michael Stewart, June 10, 2019.

Germination and growth
Cardwell, V.B., E.A. Oelke, and W.A. Elliott. 1978. Seed dormancy mechanisms in Wild Rice (Zizania aquatica). Agronomy Journal 70 (3): 481-484.

Whigham, D.F. and R.L. Simpson. 1977. Growth, mortality, and biomass partitioning in freshwater tidal populations of wild rice (Zizania aquatica var aquatica). Bulletin Torrey Botanical Club 104: 347-351.


Mary A Leck,
Emeritus Professor of Biology, Rider University
Friends for the Abbott Marshlands

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