A complete collection typically includes either flowers or fruit and underground portions of the plant. Certain groups of plants have more specific collection guidelines (such as sedges and woody plants). When a rare plant population appears to be secure, a collection is made of all or part of the plant. For conservation purposes, the roots of rare species are often not collected and only the portion of the plant required to make positive identification is collected. Occasionally only a photographic record is made of a rare species if it is adequate for positive identification.
The freshly collected specimen is placed within a sheet of folded newspaper with the leaves, flowers, etc, arranged in a natural position but clearly showing the diagnostic features. The sheet is placed between blotters and ventilators, then put in a press and compressed by tightening straps around the press. The press typically accommodates many plants. It is placed in a warm and dry environment soon after collections are pressed to ensure proper drying and preservation. After several days of drying, the plants are removed from the press and stored in a dry place until identification can be verified.