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A: Unfortunately, there are no reliable sources for this information. The best place to start is to find a similar plant already in the plant database.
If you cannot find a similar plant, consider the frost hardiness of the plant. For example, most hardy perennials can be safely planted outside before the last Spring frost. The next category of plants are usually considered hardy annuals; these are best planted out shortly after your projected last frost date. Finally, there are a number of half-hardy or tender plants which don't tolerate frost at all; these should be planted out well after your last frost date (usually at least three weeks) to avoid frost damage.