This critical thinking activity is really more about learning plant vocabulary and traits than searching for items. It also works for all age levels by adapting the vocabulary. You can develop your own list by touring your schoolyard to see what is available.
Below are 10 suggested things that can be adapted for your plant hunt. This version includes the list with the appropriate vocabulary for three age levels: 2-3, 4-6, 7-adult. Make sure to describe the exact area within which they can hunt for the objects. Also, obviously no one can collect a tree, so tell them that if the object is too big (or will hurt the plant to collect it), they can just name or draw it on their answer sheet.
When you research information you must cite the reference. Citing for websites is different from citing from books, magazines and periodicals. The style of citing shown here is from the MLA Style Citations (Modern Language Association).
When citing a WEBSITE the general format is as follows.
Author Last Name, First Name(s). "Title: Subtitle of Part of Web Page, if appropriate." Title: Subtitle: Section of Page if appropriate. Sponsoring/Publishing Agency, If Given. Additional significant descriptive information. Date of Electronic Publication or other Date, such as Last Updated. Day Month Year of access < URL >.
Amsel, Sheri. "Learning About Plants - Scavenger Hunt" Exploring Nature Educational Resource ©2005-2019. January 22, 2019
< http://www.exploringnature.org/db/view/Learning-About-Plants-Scavenger-Hunt >