Agriculture and Agri-Food Canada's (AAFC) National Collection of Vascular Plants (DAO) starts with the most primitive vascular plants that existed with the early dinosaurs and proceeds to those that evolved more recently along the major lines of evolution. For example the collection begins with ferns and fern allies, continues to conifer trees, pondweeds, grasses and sedges, then lilies and orchids. Willows and buttercups begin another series of branches which ends with mints and sunflowers. This traditional sequence is the same as that used in many botany textbooks.
The evolutionary or relationship sequence is useful for finding things in some complex groups. For example, the sedges are given MacKenzie's numbers reflecting relationships. A particular species can have many names but only one number so all synonyms are filed together. This forces all related material together more so than an alphabetical system which results in related specimens with different names being widely scattered. Within each species the specimens are organized into geographically coded folders:
- Canada (Manila folders)
- United States (Orange folders)
- Europe, Australia, Asia, Africa (Blue folders)
- Mexico, Central America, South America, West Indies, Bermuda, Bahamas (Gold folders)
- Cultivated Plants (Green folders)
- Associated information including sight records, letters, and photos, is filed in red folders within the appropriate coloured folder.
- Hybrids are filed after the parental species name which comes first alphabetically.
- Type specimens are wrapped in protective manila folders with hatched edges and filed within the geographic colour system.
- Vouchers for chromosome number determinations have a red stripe visible on the end of the sheet near the label.
There is a particularly good representation of crops, crop relatives, and horticultural plants. Among the vouchers for cultivated plants are many examples of important cereal cultivars (Avena, Hordeum, Triticum) including Triticum aestivum "Marquis", the short-season Marquis Wheat developed by AAFC researcher Charles Saunders in 1906. This famous cultivar promoted the development of agriculture in the Canadian Prairie Provinces and became a major crop in the Canadian agricultural economy. It also supplied food for much of Europe during the First World War. Many other collections of cultivated plants are maintained and include:
- Vegetables (such as carrots (Daucus carota var. sativa), squash (Cucurbita spp.) and tomatoes (Lycopersicon esculentum)
- Some fruits such as examples of many of the strawberry plants maintained in the AAFC clonal genebank
- Fodders including the world's largest collection of native and cultivated alfalfa (Medicago sativa)
- Ornamentals including Shasta Daisy (Leucanthemum vulgare) and Barberry (Berberis sp.) cultivars developed to prevent transmission of the rust pathogen that attacks cereals. The collection also includes representatives of most of the ornamental trees and shrubs growing in the National Arboretum on the Central Experimental Farm.
The voucher specimens for major published work on the flora of Canada (such as the recently published "Flora of the Yukon Territory," NRC Press, 643 pp.) are contained in the collection where they are available for checking and as a foundation for future research on the native.