One of the biggest challenges I face with a large garden is keeping track of when to start my seeds indoors and when to plant the seedlings outside. If I start them too early, then the plants can become huge and root bound weeks before it is time to move the plants outdoors. If I start them too late, then I end up with smaller plants than I had intended for planting outside, or even missing the optimum sowing dates completely.
This seed starting chart is for Plant Hardiness Zone 6B and assumes good weather for the “start outdoors” options. It also assumes planting out from mid-April to mid-May, as the “last frost” in my area is at the 50% chance there are no late frosts in May. (Hah). I adjust as needed for warmer or colder than usual spring weather and am updating it regularly.
For my area:
The average last frost in Spring is by April 30th, but there is still a small chance of frost between May 1st and May 10th.
The average first frost in Autumn is between October 20th and November 1st.
The frost-free growing season is around 170 days.
With this timetable, I start plants that need a longer growing season indoors and under lights, as this gives me a head start.
I move my more cold-tolerant varieties to the garden in mid to late April and plant out the heat lovers like tomatoes and peppers by mid to late May, after the ground has warmed up.
It’s a good idea to keep a journal of your seed starting dates, along with when the plants germinate and how they grow. This will make it easier to find and adjust your schedule to the dates that work best for your area and setup. I’ve moved some of my own start dates a little later because the plants were getting too big too soon for the space and pot sizes I have.
Treat the charts as a general guideline: the time for germination and growth rates can vary widely depending on your individual seed-starting setup and growing conditions. For example, using a heating mat will speed up the number of days to germination, and the temperatures in your seed-starting area can impact the growth rate of seedlings. Good lighting is important for getting your plants off to a healthy start.
This is the evolving schedule I use for starting seeds and transplanting seedlings. It is a work in progress and will be updated regularly to include more vegetable and flower varieties and occasionally to tweak the start and transplant dates.
Winter and Spring Seed Starting Schedule for Zone 6
Weeks before last frost (April 30th)
Start Seeds Indoors
Start Seeds Outdoors
celery, celeriac leeks
leeks broccoli eggplant ground cherries
leeks Hot Peppers broccoli Sweet Potato slips eggplant ground cherries
Vegetable and flower seed starting and planting schedule for Zone 6
Garden planning and preparation, seed sowing and starting… with gardening, timing is everything, and knowing how many weeks you are before the first and last frost dates is important in determining when to start your seeds indoors, sow seeds outdoors, and transplant seedlings outside. Even so, the dates are averages and can vary depending on the weather on any given year. Watch the weather reports closely when preparing to plant outdoors.
Know your garden zone and your first and last frost dates.
This seed starting calendar below is set up for plant hardiness zone 6 but can be adapted to your zone. To calculate when it is time to start your seeds and when to move your plants outdoors, you will need to know the first and last frost dates for your area and the length of your growing season. You can find this information by entering your zip code at plantmaps.com .
More detailed information on freeze and frost dates with temperature ranges can be found on garden.org.
Knowing the dates for your zipcode is helpful because even a few miles can change the local environment significantly.
For my area in the suburbs west of Cleveland, Ohio:
The average last frost is between May 1st and May 10th.
The average first frost is between October 20th and November 1st.
The frost dates are not a guarantee, they are an average. For my area, there is a 50% chance that the last frost will be by April 30th, and a 10% chance that the last frost will happen as late as May 15th. By way of example, here are the last freeze dates and the lows on that date here in my suburb of Cleveland for recent years. From these results I can tell that I’m fairly safe if I plant things out any time in May, provided I am prepared to provide protection to my plants just in case. I will note that while these were the last frost days, there were in many of these years more than a few nights even in early May in that came close, with lows reaching 34 degrees.
Temperatures shown in Fahrenheit.
2021 – while much of April was warm, we had 7 inches of wet snow on April 21st, a low of 31 degrees on April 22nd, and a light frost with a low of 37 on April 30th. On May 9th we had 35 degrees with brief period of sleet and freezing rain, and on May 10th it hit a low of 34 degrees.
2020 – a low of 30 degrees on May 9th and 32 degrees on May 12th
2019 – an amazingly early April 2nd with a low of 32 degrees
2018 – April 29th at 30 degrees.
2017 – April 8th: 30 degrees.
2016 – April 10th – 23 degrees.
2015 – April 24th – 28 degrees.
2014 – April 15th – 25 degrees
2013 – April 26th – 30 degrees
2012 – April 29th – 28 degrees
2011 – April 3rd – 32 degrees
2010 – April 10th – 32 degrees
When determining the best dates for seed starting and transplanting out for your area, consider your local growing conditions. For Ohio the recommendations for planting some seeds or transplants outside can read “as soon as the ground can be worked, in March or April”. It’s possible that the ground can be worked in March in other parts of Ohio, but here in my backyard it’s still cold and muddy, so I usually don’t start planting anything until April.
With a 50% chance that the last 32-degree day is at the end of April and a 90% chance that there will be no more frosts by May 12th, I stagger my plant-out days, with more cold tolerant varieties hardened off and planted outside in late April and early May and waiting to plant the fussier plants like tomatoes and peppers until mid-May. This also benefits the tender plants, as the ground is warmer by that time.
First Frost Dates and Your Growing Season
The number of days between the first and last frost dates is the length of your growing season. This helps in deciding what you can grow that will ripen and be ready for harvest before the first frost in the fall, as well as the best time for fall planting. It also helps for planning when to start your fall season crops, as some vegetables are best started late so that they don’t bolt during the hottest days of summer.
What garden zone am I in? This information will tell you what plants are hardy in your area and therefore can be grown with assurance that they will have the best chance of surviving and even thriving in your local environment. By starting with your garden zone and then evaluating for the micro-climates in your yard, you can identify areas where individual plants will do better… you may even find a sunny spot against a south-facing wall where you can grow a plant variety that is normally rated for a warmer zone.
The USDA published its updated plant hardiness zone map in 2012, in which they incorporates improved accuracy and detail, along with recent warming trends. Many areas were shifted an entire zone from the 1990 map, and even more from what I have come across in old gardening books from the 60’s and early 70’s.