Cones that are used a lot in cooler zones to protect newly planted seedlings from cold weather and birds. Usually made of plastic or a very heavy translucent waxed paper.
The sweet and sticky syrup secreted by aphids and other sap-sucking insects. It then sometimes gets mouldy fungus on it. Should be washed off with a soapy water rinse.
Annual vegetables or flowers that grow quickly to flowering stage, at the expense of their best overall development, and go to seed (i.e. dill in hot weather).
Any plant material that will support a parasite. Oak trees will host mistletoe that will create damage and oaks can also host Spanish moss that does no harm.