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Submitted by: Esther Shigezawa
University of Hawaii - Manoa
Honolulu, HI

Limu is the Hawaiian term for algae or seaweed. All limu in Hawaii are edible but flavors and textures vary greatly. Scientists collect and press plant specimens to use for reference and study. Scientists have a procedure for pressing and identifying plants. A collection of pressed specimens is called an herbarium.

Algae are aquatic plants, therefore, the pressing process requires that the specimens be submerged in water. Pressing and drying can be done easily, even at home with readily available resources such as newspaper, waxed paper, and several heavy books.

This activity uses the basic algae pressing techniques but, instead of selecting only one type of algae per sheet, you may create a collage of seaweeds by arranging a few different types on one sheet. This, then, can become a notecard, a paperweight, or can be framed.


  1. To learn algae (seaweed) pressing
  2. To create decorative cards using pressed algae

  • pan with water
  • paper (index cards, botany paper or heavy cardstock)
  • waxed paper (cut into pieces to fit the card/paper; need one piece per card)
  • old newspaper (to absorb the moisture)
  • pieces of cloth/old sheets (cut into pieces to fit over the cards/paper)
  • brushes (to work the specimens)


  1. Spread newspaper on counter top to keep area dry.
  2. Fill pan with water,about 1/2 inch deep.
  3. Select algae to be used.
  4. Place algae in pan of water.
  5. Place card/paper on bottom of pan, under algae.
  6. Spread, trim, arrange algae on paper while under water. You may use the brush for this.
  7. Gently lift paper from water with the arranged algae.
  8. Carefully drain as much water off as possible.
  9. Place the card/paper with arranged algae on a folded section of newspaper.
  10. Place a piece of waxed paper over the arranged algae.
  11. Place a piece of cloth over the waxed paper.
  12. Place another layer of folded newspaper over the cloth.
  13. Gently place entire bundle into plant press.
  14. Check bundle after 24 hours. Newspaper and cloth may need to be changed if much water has been absorbed. If you do not removed wet cloth and newspaper, arrangement may become moldy.
  15. After three to four days, remove arrangements and glue card/sheet onto construction paper cut about 1/4 to 1/2 inches wider and longer than arrangement sheet (this will frame the arrangement).
  16. If available, domed clear glass paperweights could be fit over the algae arrangements. Another idea is to place these arrangements in lucite frames.

A. Identifying algae

  1. If you intend to identify the seaweeds, instruct students to press only one seaweed on a sheet.
    a. Use a seaweed key to classify them.
    b. Label appropriately with seaweed name, location collected, depth, substrate, date and collector's name. Glue this label on the lower right corner of the sheet holding the seaweed.
  2. Create a class herbarium by combing all specimens mounted by students.
B. Questions related to seaweed pressing process
  1. How might you rehydrate a pressed specimen? Compare the appearance of a rehydrated specimen and a fresh specimen.
  2. Why do seaweeds stick to the paper when they are pressed?
C. Library research
  1. Research one or a number of products of algae and how they are used.
  2. Find as many products on the market today that contain algin (a product of algae).
  3. Learn what carrageenan is and how it is useful.
  4. Find out what agar is, how it is used and why it is important to scientist.
D. Cooking algae:
    Find out the various ways seaweed is prepared as food by different cultures. Try some recipes and share with your classmates. Consider holding an "ALGAE COOKFEST".

Klemm, E. Barbara, et al, The Living Ocean, Biology and Technology of the Marine Environment , HMSS, Hawaii Marine Science Studies, Third Edition, University of Hawaii's Curriculum Research & Development Group, Honolulu, Hawaii, 1995, pp. 293-312.

This is one of six lessons in "MIXED-PLATE BIOLOGY, HAWAIIAN STYLE", a collection of biological activities that values the cultures of modern Hawaii's multicultural population. The collection includes:

Hawaii is a land of immigrants. The Hawaiians are believed to have arrived around 1000 AD from the Marquesas Islands in the South Pacific. Starting in the 18th century, Europeans and Americans arrived usually involved in missionary work or seafaring trades. Once agricultural plantations of sugar and pineapple were established in the 20th century, workers arrived from China, Japan, Puerto Rico, Portugal, and the Philippines.

Since the plantation days, immigration has been largely from Southeast Asian nations of Vietnam, Laos, Cambodia, and Thailand; Korea; the South Pacific nations of Samoa and Tonga; the Philippines; as well as the US mainland. As ethnic diversity increases in our classrooms, let's draw from the various cultures to personalize the concepts of biology.

(About the title: a Mixed Plate is a unique lunch that evolved as new immigrant populations arrived in Hawaii and can include pork adobo from the Philippines, teriyaki beef from Japan, kim chee from Korea, bean soup from Portugal, chow mein from China, traditional Hawaiian foods such as lau lau and poi and of course two scoops of rice.)

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