Herbarium is a collection of plants. So I don't think it is one specific plant. What the nurse may be trying to say is that you are allergic to certain plants that they tested you for, such as grass and/or trees and/or weeds and/or fungi (mold)...but it is best if you try to ask the doctor and I would also ask for a copy of the test results yourself, so you can see what all you were tested for.
Gluten & Sulfite Sensitivity, Many Food/Inhalant/Medication Allergies & Intolerances, Asthma, Gut issues (dysmotility, non-specific inflammation), UCTD (Lupus?), Osteoporosis, Anemia, T- & B-Cell Lymphopenia, malabsorption/malnutrition, Lyme Disease (Igenex Lab IgM WesternBlot positive/CDC negative), etc.
Meds: Pulmicort, Injectable Vitamin B12, Herbs, Nutritional Supplements, Homeopathy.