Monday, March 5, 2012

Seed Starting/Frost Dates for Philadelphia

By Lois Fischer

The times, they are a’changing…. particularly when it comes to the frost date in Philadelphia. With the recent changes in our climate zone number, the average frost-free date has been pushed back from May 15 to April 20 or so. Spring frost date is the average date of the last frost. The operative word here is average. As we all know, the weather can confound even the meteorologists.  So I wouldn’t be in a rush to set out my tender basil, tomato, eggplant and pepper plants. In fact, I don’t start planting tomatoes until the second week in May. One unexpected cold night can turn those lovely green leaves to black, wasting all of your time and energy spent raising those little beauties from seed. At the nursery where I work, I advise folks not to rush the planting of cold sensitive vegetables. Waiting an extra week to two will not dramatically change your harvest time and may save a trip to the garden center for replacement plants. However, if you just cannot wait to put those babies in the soil, I have two bits of advice. Keep your eye on the daily weather forecast for the nighttime temperatures and have floating row covers ready in case the thermometer drops into the upper 30’s to low 40’s. Vegetables that are cold tolerant – lettuces, peas, arugula, spinach, kale, broccoli, collards, mustard greens and the like – can be planted in early spring as soon as the soil can be worked. “As soon as the soil can be worked”… what does that mean? During most winters, Philadelphia will receive a fair amount of rainfall or snowfall, making the soil wet and heavy. The soil needs to dry out so it can be easily turned. Seeds and seedlings planted in soggy, cold soil will rot. So, ignore the old adage of planting peas on St. Patrick’s Day unless it has been a dry and warm winter. Waiting an extra week for the soil to dry out and warm up a bit will mean better seed germination and happier seedlings. 

Seed Starting Chart from

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  1. To encourage butterflies to hang out in your garden as long as possible, provide food sources for the larvae (caterpillars) as well as nectar plants for the adults (butterflies). philadelphia car accident

  2. I advise folks not to rush the planting of cold sensitive vegetables.