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 organicgardening.com

Timing is everything. To start your seeds on time, you need to know when in relation to the frost-free date in spring to plant them. If you need help determining your spring frost-free date, call your county extension agent who can tell you for certain.
Creating Your Seed-Starting Plan

Print the seed starting chart below.
Write your frost-free date in the blank space at the top of the chart.
Get a calendar and add or subtract the number of weeks in the "Safe to Set Out Time" column. This is the "Setting Out Date" when you can safely plant the crop to the garden. Write it in the last column.
Take each date from Column 5 ("Setting Out Date"), subtract the number of weeks shown for that crop in column 3 ("Weeks from Sowing") and record that date in column 2 ("When to Start Inside").

YOUR SEED-STARTING PLAN
The Spring Frost-Free Date in My Garden is_______________
CROP	WHEN TO START INSIDE	WEEKS FROM SOWING	SAFE TO SET OUT TIME (RELATIVE TO FROST-FREE DATE)	SETTING OUT DATE
Basil		6	1 week after
Beets*		4-6	2 weeks before
Broccoli		4-6	2 weeks before
Cabbage		4-6	4 weeks before
Cauliflower		4-6	2 weeks before
Collards		4-6	4 weeks before
Corn*		2-4	0 to 2 weeks after
Cucumber		3-4	1 to 2 weeks after
Eggplant		8-10	2 to 3 weeks after
Kale		4-6	4 weeks before
Kohlrabi*		4-6	4 weeks before
Lettuce		4-5	3 to 4 weeks before
Melons		3-4	2 weeks after
Mustard*		4-6	4 weeks before
Okra*		4-6	2 to 4 weeks after
Onions		6-8	4 weeks before
Parsley		9-10	2 to 3 weeks before
Peas*		3-4	6 to 8 weeks before
Peppers		6-14	2 weeks after
Pumpkins		3-4	2 weeks after
Spinach		4-6	3 to 6 weeks before
Squash		3-4	2 weeks after
Swiss chard		4-6	2 weeks before
Tomatoes		6-8	1 to 2 weeks after
* These crops are usually direct-seeded outdoors, but they can be started inside.