Many plants may enter the United States from foreign countries, provided they meet certain entry requirements. Entry requirements vary by plant, but the following requirements universally apply:
If you bring back 12 or fewer plants that are not prohibited and have no special restrictions, you do not need a USDA-issued import permit. Special restrictions apply to certain plants and may include requirements such as a permit, post-entry quarantine, treatment, or Endangered Species Act or Convention on International Trade in Endangered Species of Wild Fauna and Flora documentation.
Plants and seeds must be accompanied by a phytosanitary certificate from the country of origin showing the plants meet entry requirements for the United States.
Plant roots should be completely free from soil and other growing media. They should be bare-rooted (no soil or other growing media attached to the roots).
Select plants that look healthy. Plants must be free of pests, including disease symptoms and insect damage.
Wrap plants in damp newspaper or similar material to prevent them from drying out. Roots may be secured in a plastic bag.
Twelve or fewer plants are inspected by CBP at the first port of entry. Cut flowers are also subject to inspection. Thirteen or more plants must be inspected by USDA personnel at the nearest plant inspection station. Plants requiring USDA inspection must be mailed directly to a plant inspection station. If the inspector finds plant pests that could cause harm to other plants, or if the plants do not meet entry requirements, they will be refused entry. This means that the plants will either be destroyed or you must return them to the country of origin at your expense.
You can contact a plant inspection station nearest to you and ask whether the plant material you wish to import (including live plants, bulbs, corms, cuttings, root crowns, seeds, etc.) is allowed. For a list of inspection stations, visit http://www.aphis.usda.gov/import_export/plants/plant_imports/