Plant collecting

Proper pressing and mounting techniques are critical to the longevity of a collected plant sample. Properly preserved plant samples can last for hundreds of years.[5] The New York Botanical Garden itself holds plant samples that date back to the Lewis and Clark expedition of 1804–1806.

A book with a weighted object on top of it can be used to press plants

After cleaning the sample of any mud or dirt, the next step is to press the sample. Some samples may press better if they have been left to wilt for a few days. However plants should never be allowed to spoil or decompose before pressing, as this will impact the quality of the dried product. Plant presses are most commonly constructed with two flat smooth pieces of wood, and some type of compression mechanism. Compression may be accomplished with tightened nuts and bolts on the corners of the press, with tightened straps around the press, or by placing weights on top of the press. A book with a weighted object on top of it can also act as a press.[6] When placing in the press, plant samples should be sandwiched between a few layers of absorbent blotter. Newspaper and cardboard are two common choices for blotter material. When arranging the plant in the press it is important to remember that the dried plant product will be fragile and inflexible, so position the plant exactly as you wish the final product to appear. Tighten the press and wait approximately a day to check up on the plant. The blotter should be taken out and replaced with dry blotter roughly every 24 hours. Complete drying time will vary depending on the type of plant, but is generally 7–10 days. Fleshier plants such as succulents will take longer.[7][5][4]

After the plant sample has been sufficiently dried and pressed, it must be mounted. The quality of mounting not only impacts the appearance of the plant sample, but also determines the rate of deterioration the sample will experience. Herbarium quality mounts use specialized paper for the best protection against deterioration.[8] This paper can either be 100% alpha cellulose paper or cotton “rag” paper. These types of paper are ideal for preserving plant samples because they are acid free and pH neutral. Samples can be strapped to the paper with linen tape, or glued onto the sheet. If glue is needed, it is recommended that Grade A methyl cellulose mixed with water be used for optimal deterioration resistance.[3]

In order for plant specimens to be kept in good condition for future reference, adequate storage conditions are needed. The storage space should be kept in a low light, low humidity environment. The temperature of the storage space should be kept cool, between 50 – 65 degrees Fahrenheit or 10 – 20 degrees Celsius.[9]

It is important to keep the storage space free of harmful pest. It is recommended to protect the specimens by sheathing the sheets in sealed plastic bags. Various pesticides may also be used to protect the storage space from pest infestation. If pest infestation has already occurred, the samples should be frozen for three to four days. Freezing new additions of plant samples is a suggested preventative measure against the introduction of pest to the storage space.[8][3]

Some specimens cannot be compressed, degrade when dried, or require other techniques for preservation and storage.

Large seeds or fruits may be stored in boxes without compression. Aquatic plants and delicate plants may be stored in a liquid preservative. Cacti may be stored in ethanol.

Voucher specimens are select herbarium specimens. What distinguishes these specimens from others is that a voucher specimen is a "representative sample of an expertly identified organism." These specimens are usually associated with a professional research article and are considered to be more official references than a typical herbarium specimen. Voucher specimens can be useful in many ways such as use for comparison when scientists think they have found a new species or when dichotomous keys have narrowed the possible species down to a few that have minute differences.[12]

Huntington Library Desert Garden Plant Theft Prevention Sign

The hobby and practice of plant collecting is known to have been the cause of declines in certain plant populations.[15] This can be the result of hobbyists being oblivious to the status of a particular species, collectors of valuable species for profit, or researchers over collecting to fill slots in herbaria. This issue can be solved with proper research on the status of species before a plant is collected and taking the smallest sample possible. Threatened species may be listed in databases, such as the Cites (Convention on International Trade in Endangered Species) database,[16] though poachers have been known to use these resources to identify potentially valuable species.[17] Additionally, botanical gardens themselves can raise awareness of plant poaching. The Huntington Library, Art Museum, and Botanical Gardens introduced a sign to deter plant theft in their Desert Garden.

There are some historical examples of widespread plant collecting that have led to extinction or near extinction of species. Many of these instances have further led to an increase in modern theft of these species, given their rarity in the modern day.

An early example includes the Victorian Fern Craze, also known as Pteridomania or Fern-Fever, which, beginning in the 1830s, drastically reduced the numbers of various fern species in the UK. In particular, many in the Woodsia genus as well as the Killarney species.

Another Victorian craze known as Orchidelirium similarly led to extinction of several species. The Lady Slipper Orchid was declared extinct in the UK in 1917 and later rediscovered in 1930 as a single wild plant in the Yorkshire Dales, the only remaining site in the UK for these plants.[18][19] Once found, the plant was guarded 24 hours a day.[20]

In 1956, the UK's last remaining plants of the Spiranthes aestivalis, Summer Lady's-tresses orchid, were stolen.[20] The orchid is still classified as extinct in the UK.[21]

Many botanical gardens have been the target of plant theft, given the nature of their collections, which often house rare and valuable plants.

In March 2021, the San Diego Botanic Gardens faced an incident of attempted plant theft when a woman was seen taking a clipping from one of the gardens’ collections. When confronted, she returned the clipping, but left before authorities arrived. Garden staff members believed that she got away with other clippings as well. In an interview, the president and CEO of the gardens attributed an increase in theft to “the surge in houseplant interest, which is driving plant prices higher and leading to less ethical plant-sourcing behavior.”[22]

In 2014, Kew Royal Botanic Gardens saw the theft of one of twenty-four of their Nymphaea thermarum, the world's smallest water lily ever discovered. There are about 100 of these species left, which survive solely in botanical gardens, last seen in the wild in 2008.[23][24]

In 2014 in two separate incidents, a total of twenty four cycads were taken from the Kirstenbosch National Botanical Garden in Cape Town, South Africa. Twenty-two of those twenty-four were Albany cycads, a species on the critically endangered list with only an estimate of 80 left in the wild. The total cost of the theft amounted to an estimated 700,000 rand, or just over $45,000.[25]

In September 2020, Christchurch Botanic Gardens in New Zealand had a variegated monstera stolen from its orchid house.[26]

Plant theft is not solely limited to botanical gardens with rare collections. It extends to private property and local businesses. The practice of taking fallen plant leaves or clippings for the purpose of later propagating from those pieces is known as Prop-lifting and is known to be discouraged or even unethical. CA Penal Code § 384a prohibits cutting of plants from both private and public property, stating “A person shall not willfully or negligently cut, destroy, mutilate, or remove plant material that is growing upon state or county highway rights-of-way” and “A person shall not willfully or negligently cut, destroy, mutilate, or remove plant material that is growing upon public land or upon land that is not his or hers without a written permit from the owner of the land, signed by the owner of the land or the owner’s authorized agent, as provided in subdivision.”[27]