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Making Plant Collections
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Introduction
Plant specimens that are pressed, dried rapidly and then stored in the dark away from insect pests under normal levels of humidity found in temperate countries will remain in good condition for hundreds of years. Such specimens, from the early 1700s, have served as vouchers, commonly called type specimens, of plants that served as the basis for many of the scientific names presently in use. Such collections of dried plants, whether small and stored within a scrap book or box or large and occupying many rows of specially constructed metal cases within a room or building of a research institution, constitute a herbarium - a hortus sicus - or dried garden. Some of the earliest such collections were made of specimens from the gardens of nobility and wealthy merchants.
No specialty equipment is required for making good plant collections. Much of the equipment and supplies are usually available within the home or can be obtained and assembled at minimal cost.
Collecting Plants
Precautions
Novice plant collectors should be aware that permission is required for anyone wishing to collect on private property. In the case of parks, nature reserves and conservation areas on public lands, special permits are invariably required. Collecting permits may only be granted, however, to those involved in serious studies that contribute to the better understanding of the flora of such special lands.
Collectors should also become familiar with what species are considered to be provincially or nationally rare and possibly at risk so that their collecting activities do not contribute to the decline of populations at risk. Information on such species can be obtained by contacting the Secretariat of the Committee on the Status of Endangered Wildlife in Canada (COSEWIC 1997) for species at risk nationally and for contacts within the various provincial addresses of wildlife agencies that participate in COSEWIC. Six provincial Conservation Data Centres and Natural Heritage Information Centres have also been established (AB, BC, MB, ON, QC, SK). These agencies can provide comprehensive listings of species that are at risk in their provinces (CDCs 1997).
When to Collect
Although plants and plant parts can be collected at all seasons and under all weather conditions, it is best to collect plants during dry sunny weather. Plants collected when there is no surface water present will dry more quickly and retain their colour better and there is less chance of moulds developing.
How to Collect
Uproot
small specimens carefully with a large blunt hunting knife or trowel and remove soil and debris. Root systems and underground stem modifications such as rhizomes and tubers should be included because they may be diagnostically important. Tall herbaceous specimens should be uprooted and, if necessary for ease of pressing, a portion of the stem may be discarded as long as the total height and any pertinent features are recorded in the field notes. The stems and leaves of tall herbs can generally be folded one or more times so that they will fit within the field storage container being used. Collections from shrubs and trees may be made by cutting off a suitable portion of a branch about 30 cm long. Notes on the size and growth habit of the plant should be made in a field record book. This should be done in pencil or waterproof ink or on a slip of paper that is kept with the specimen until the data are recorded at the time of pressing.
Unless required as vouchers for ecological or other detailed survey projects, only plants or portions of large specimens with reproductive structures should be collected. Reproductive structures include flowers, fruits, cones, and the fertile leaves or shoots of ferns. Bulky structures, such as cones, should be placed in paper bags and numbered to correspond with the leafy branchlets taken from the same specimens.
One of the simplest and most effective means of carrying plants that have been collected is to place them into plastic bags. Freezer bags of a size normally used for turkeys or chickens are convenient for collecting purposes. However, any reasonably-sized bags that are readily available, such as grocery store packing bags, can be used. For convenience in seeing the contents, clear bags are preferable. If large numbers of plants are to be collected at one site, the delicate plants should be placed in a separate bag. Similarly, plants from different habitats or from different monitoring plots should be stored in separate bags. A brief note with the locality and habitat description and other pertinent data placed in the bag is an easy means of recording such field data and avoiding later confusion. Groups of plants or replicate samples from a shrub or tree can be held together with commercially available tags with a looped string attached. This is used to fasten the stems or plants into a small bundle. Pertinent information is written on the label in pencil or waterproof ink.
If separate bags are used for grouping specimens from different habitats or from different monitoring plots, a number of them can be conveniently carried within a larger plastic bag, preferably white or light-coloured to minimize overheating within the bags as they are carried about in the sun during the course of the day. Plastic bags containing specimens should be kept shaded as much as possible while in the field to avoid undue heat stress and wilting. Plants are easier to arrange for pressing and make better specimens when they are still quite fresh. If delicate submersed aquatic plants are collected, these can be kept separately in small clear bags. If flowers are present on the aquatic plants, care should be taken that they do not get wet from contact with the submersed parts.
Pressing
The outer covers of a traditional press are 30 x 45 cm and consist of a rectangular latticework of thin hardwood slats riveted together to form rigid lightweight surfaces that permit the layers of press materials and plants to be firmly strapped together for drying. However, two pieces of 6 mm plywood, cut to size, also make suitable press covers. The press materials consists of a stack of alternating layers of thick blotting felts or sheets of 6 mm thick polyurethane foam and cardboard ventilators, with about 25-30 of these felt or foam units making up a complete press.
The
standard press size was based roughly on the traditional size of one half of a fully opened sheet of newspaper cut in half and folded in half at right angles to its length. Such a folded sheet made a convenient size for drying and storing a specimen that would be mounted on a stiff mounting sheet of paper that measured around 29 x 42 cm. Mounting sheet standards, however, vary somewhat between institutions. As well, presses for work in alpine or arctic areas were made smaller to take into account that tundra plants tend to be shorter in stature. Current newspaper page sizes also tend to be smaller. Any convenient size of press will do.
The cardboard ventilators in professional presses used by institutions have continuous open channels running between the short dimensions of the cardboard. This allows heated air to travel through the press as it lies on one of its open sides over a source of heat. Such ventilators can be made from large discarded packing boxes. Sheets of felt driers were once the commonly used absorbents in presses. They also help to flatten plant parts so that they do not wrinkle excessively in drying. Sheets of foam obtained from upholstery supply companies, however, are superior for flattening plant parts and allowing fast drying. Unlike the felts or additional layers of newsprint that can be used to absorb the moisture from the plants as they dry, foam sheets do not absorb the moisture and do not have to be replaced during drying as was once the case with felt driers, especially when no artificial heat was used.
Specimens should be pressed as soon as possible after they have been collected. They are prepared for pressing and drying by arranging each neatly between a folded sheet of newsprint of suitable size to fit the press. Several small specimens can be pressed within a single sheet. The print from a newspaper will not come off during the drying process. Plants with fleshy bases or with thick bulbs or root systems may be dried best by cutting these unwieldy structures in half lengthwise or into thin sections as an aid to drying. Delicate aqautic plants may need to be placed in a tray of water in order to separate the parts. A sheet of wax paper is then submersed under the plants and the leaves and stems of the aquatic are spread out to minimize overlap that would hinder examination of critical parts for identification. The wax paper with the fragile aquatic is then placed within a newsprint folder and placed in the press.
A unique collection number should be written on the outside of each newsprint folder and this same number, and data on flower colour or growth habit that will likely change in drying, should also be entered into a record book or the field notebook. Flower colours will fade or change on drying and should be recorded as aids to identification. Other pertinent notes on the locality and habitat should also be written in the field book. If the identity of the plant is known, the name can be written on the outside of the newsprint folder.
The newsprint folder containing the suitably arranged specimen with leaves separated and examples of both upper and lower leaf surfaces evident is placed on a cardboard ventilator followed by a drier felt or foam sheet. If the felts are relatively thin or the foam sheets are old and compressed, felts or foam may be required on either side of the newsprint folder containing the plant. The overall dimensions of the press materials are of a size slightly larger than that of the newsprint folder. When a manageable bundle has been stacked up the press is cinched tightly with straps ready for drying.
Drying
When in the field, the press may be placed in the sun for drying or on the roof rack of an auto with the open end facing the direction of movement so that air is forced through the press. It is preferable, however, to use a source of flameless heat such as a tent heater or, where electricity is available, a low wattage hot plate or 2-100 watt light bulbs in shallow fixtures. The press is supported on a frame at least 20-30 cm above the heat source, depending on intensity, to avoid scorching the lower side of the press and the plants within. The frame and heat source are enclosed by a cloth to create a vertical draft through the press. Thumb tacks or velcro strips fixed to the frame and cloth can be used to attach the cloth. The edge of the cloth can also be fitted along the top edge of the press to enclose both the sides of the press, or presses, and the drier stand. This extends the chimney effect in maintaining the heat within the press. This is particularly advantageous in keeping the entire press warm when in the field and nights have become cool. If only one portion of the top of the drier frame is used, the portion not covered by a press should be closed with a piece of cardboard to keep the heat in.
To
promote efficient drying, the corrugations of the cardboard ventilators must run between the short width of the press. The press is placed on its side with the corrugations vertical to allow the warm air to rise through its centre. The straps should be tightened periodically because the press becomes loose as the plants dry, especially when felt driers are used. When foam sheets are used, they tend to expand as plants shrink and dry, thereby maintaining tension in the press. It is generally good practice to rotate the press 180 during the drying process if the heat source is relatively weak.
Presses can be elevated above the heat source in many improvised ways. A simple wooden frame with rigid or folding legs can be constructed with a cotton skirt around its bottom. Two chairs can be used to support the edges of the press with a blanket used to form a skirt enclosing the chairs and press with the electric heat source in the centre. The main requirement is that there should be ample heat and it should be directed through the corrugated channels of the press. Trial and error will quickly indicate how far from the heat source the bottom of the press should be positioned so as to avoid scorching but still provide adequate heat to dry the plants within about 24 hours. Care must always be taken that the heat source is not too strong and that no paper or other inflammable materials are close to or in contact with the heat source.
Most thin-textured plants or plant parts dry within 24-48 hours. More succulent specimens may require a longer period of time. When suitably dry, most plants become rigid. Excessive drying should be avoided because the plants become overly brittle and will tend to crumble more readily. Plants are then removed and stored in a dry location within their newsprint folders, ready for identification and mounting or storage, loose within the folders.
Mounting and Storage
To
be useful as reference material for a personal collection, dried specimens need not be mounted. They can be stored simply within their newsprint folders, with the plant name and other pertinent data written on the outside, and kept in closed cardboard boxes in a dry location. Another form of simple storage and preparation of a reference collection is that of gluing specimens or portions of plants on sheets within a three-ring binder or scrap book organized in some particular manner that is useful for the collector.
For
more professional results, dried specimens are mounted on a sheet of stiff, white, acid-free mounting paper, about 30 by 42 cm, having a 100% rag content. They are fastened by applying narrow beads of white (polypropylene) glue over stems and leaf stalks. Delicate structures, especially features required for identification, should not be covered with glue. Alternatively, narrow strips of gummed paper can be used. Cellophane tape is not suitable for mounting because it deteriorates rapidly with age. While the bands of glue are drying, plant parts are weighted down with metal washers of sufficient weight to hold the parts flat to the surface of the paper. Washers can be purchased in bulk at larger hardware stores. If mounted specimens are placed on cardboard ventilators and small uniform blocks of wood are placed at each corner, the mounting sheets can be stacked vertically to minimize space needed to store them overnight while the glue is drying.
The addition of a label in the bottom right hand corner of the sheet, recording such information as the name of the plant, collection locality, habitat, collector, collection number, collection date, and the name of the person having identified the plant, completes the process of preparing a specimen as a properly documented voucher. It is generally best to include only a single species from a given locality on one sheet.
Example of a specimen label. The year of the North American Datum (NAD) used in deriving the map projection and preparing the topographic maps and instructions on how to determine UTM easting and northing values are given on the National Topographic System (NTS) map sheets.
Selected References
COSEWIC. 1997. Mailing list. The Committee on the Status of Endangered Wildlife in Canada. COSEWIC Secretariat, c/o Canadian Wildlife Service, Environment Canada, Ottawa. K1A 0H3.
Brayshaw, T.C. 1996. Plant collecting for the amateur. The Royal British Columbia Museum. 44 pp.
Saville, D.B.O. 1962. Collection and care of botanical specimens. Research Branch, Canada Department of Agriculture, Ottawa. Publ. No. 1113. 124 pp.
Plants of Canada
Province:
County:
Ecozone:
Map No.: Lat: Long:
Zone: UTM: __________E __________N
NAD:
Locality:
Habitat:
Collector: Date:
Coll. No.: |
Example of a mounted voucher specimen with label.
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