|I am always confused about when it's best to put plants in the ground for the summer garden. Is it a certain day in the spring or is it a matter of ground temperature|
|It's a matter of ground temperature and that can vary from year to year. In the Bronx, your last frost of the season is usually in mid- to late-April. This means in April you can plant cool season crops. These include lettuce, peas, and most of the cabbage and onion families. They grow best when the weather is cool -- in spring and fall -- and most can take at least a light frost. In much of New York, you usually plant them through the spring for early summer harvests, then again in midsummer for fall harvests. The plants are usually compact, their root systems are relatively small, and they are more sensitive to nutrient deficiencies.
About 3 weeks after your last frost the soil will have warmed up and you can plant warm-season crops. These include tomatoes, peppers, eggplant, beans, corn, and the family of vine crops that includes squash, cucumbers, melons, and pumpkins. Many are tropical plants, and they grow best when the weather is warm.
The same rules apply to flowering annuals and perennials. Some grow well in cool soils, others perform best in warm soils. You can take your cue from the types of plants that are available in garden centers. Cool season plants such as primroses, pansies and snapdragons will be available in April; warm season plants are typically available after Mother's Day.
Hope this helps clarify things for you!