You can use the information and link on our Spring Frost or Freeze Dates page to look up typical last-frost dates for spring in your area. (These are always averages...every year's date will be different based on weather patterns, so it can't be predicted with high accurately.) How far in advance of a frost something should be planted (either indoors or outdoors) will depend on the plant in question, and should be listed on the seed packet or in the plant catalog. It's safe to plant lots of species now, but that will depend on how frost-tolerant they are. For example, tomatoes might want to wait one or two more weeks because they like warm soil in addition to mild air temperatures, but a location in the city isn't as cool as the suburbs, so you are probably fine even for warm-season veggies to put them in the ground now (or very soon). Historically, Mother's Day weekend (a date chosen as an easy way to remember the timing) has been the "safe" date for just about all of Maryland for planting tender plants outside.

If you are moving out plants from indoors (like a houseplant or veggie seedlings you started inside), be sure to give the plants a few days in shade first to acclimate before gradually introducing them to any direct sun. Otherwise, putting them into sun immediately may damage the leaves and shock the plant, and it can take them a few weeks to recover with new growth.

Miri