<P> Rime is a type of ice deposition that occurs quickly, often under conditions of heavily saturated air and windy conditions . Technically speaking, it is not a type of frost, since usually supercooled water drops are involved, in contrast to the formation of hoar frost, in which water vapour desublimates slowly and directly . Ships travelling through Arctic seas may accumulate large quantities of rime on the rigging . Unlike hoar frost, which has a feathery appearance, rime generally has an icy solid appearance . </P> <P> Black frost (or "killing frost") is not strictly speaking frost at all, because it is the condition seen in crops when the humidity is too low for frost to form, but the temperature falls so low that plant tissues freeze and die, becoming blackened, hence the term "black frost". Black frost often is called "killing frost" because white frost tends to be less cold, partly because the latent heat of freezing of the water reduces the temperature drop . </P> <P> Many plants can be damaged or killed by freezing temperatures or frost . This varies with the type of plant, the tissue exposed, and how low temperatures get: a "light frost" of − 2 to 0 ° C (28 to 32 ° F) will damage fewer types of plants than a "hard frost" below − 2 ° C (28 ° F). </P> <P> Plants likely to be damaged even by a light frost include vines--such as beans, grapes, squashes, melons--along with nightshades such as tomatoes, eggplants and peppers . Plants that may tolerate (or even benefit) from frosts include: </P>

How cold does it have to be to frost plants