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Indoor Seed Starting Calendar

When to start seeds inside is calculated backwards from the time it is safe to plant the seedlings outdoors.  This is determined by the last frost date, which varies by plant hardiness zones.  Pittsburgh is USDA Plant Hardiness Zone 6, so the average last frost date in spring is around May 15, and first frost date in fall is around October 15. 

The dates listed below are for earliest harvests, but many can also be planted or re-planted later in the season.  Some varieties can also be direct-sown, unless indicated.

Vegetable

# Weeks to start seeds before   set-out date

When to start inside

Safe time to plant outside   (relative to frost-free date)

Plant outside dates

From

To

From

To

Basil

6

April 10

 May 1

1 week after

May 15

 June 30

Beets*

4-6

March 20

April 3

4 weeks before

April 17

 Aug 15

Cabbage

4-6

March 6

April 17

4 weeks before

April 17

May 15

Collards

4-6

March 6

March 20

4 weeks before

April 17

 Aug 15

Cucumber

3-4

April 24

May 8

1-2 weeks after

May 22

May 29

Eggplant

8-10

March 20

April 10

2-3 weeks after

May 29

June 5

Kale

4-6

March 6

March 20

4 weeks before

April 17

 Aug 15

Peppers**

8

March 20

 April 3

2 weeks after

May 29

 July 4

Squash

3-4

May 1

May 8

2 weeks after

May 29

 July 15

Swiss chard

4-6

March 20

April 3

2 weeks before

May 1

 Aug 15

Tomatoes**

6-8

March 27

April 17

1-2 weeks after

May 22

May 29

*Usually direct-sown, but can be started indoors.

**Must be started indoors; the outdoor growing season isn’t long enough for fruit production.

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