May, 2021 | Ohio Kitchen Garden

Ohio Vegetable and Flower Seed Starting and Planting Calendar

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 30^th, 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)	Approximate Date	Start Seeds Indoors	Start Seeds Outdoors	Transplant Outdoors
12	Feb 5th	celery
11	Feb 12th	celery leeks
10	Feb 17th	celery, celeriac leeks
9	Feb 26th	leeks broccoli eggplant ground cherries
8	March 5th	leeks Hot Peppers broccoli Sweet Potato slips eggplant ground cherries
7	March 12th	Peppers Sweet Potato slips eggplant ground cherries
6	March 19th	sweet potato slips onions Peppers Tomatoes Potato seeds cotton collards
5	March 26th	onions Tomatoes lettuce sunflower Potato Seeds cotton collards	chard – Soak overnight first
4	April 2nd	onions bunching onions Tomatoes lettuce sunflower Potato Seeds cotton collards	chard – winter sow or in ground
3	April 9th	bunching onions	beets chard – winter sow or in ground
2	April 16th	okra	beets chard – winter sow or in ground
1	April 23rd	okra	beets lettuce chard – winter sow or in ground	lettuce
0	April 30th	okra	beets lettuce Swiss Chard	lettuce onions Broccoli

Summer and Autumn Seed Starting and Planting Schedule for Zone 6

Weeks before first frost (Nov. 1st)	Approximate Date	Start Seeds Indoors	Start Seeds Outdoors	Transplant Outdoors
26	May 3rd	Brussel Sprouts		onions Broccoli sunflower
25	May 10th	Brussel Sprouts		onions Broccoli sunflower
24	May17th			Peppers Okra sunflower
23	May 24th		Okra	Peppers Tomatoes Okra eggplant
22	May 31st		Okra	Peppers Tomatoes Okra eggplant
21	June 7th		Okra	Tomatoes Okra
20	June 14th			Okra
19	June 21st			Brussel Sprouts
18	June 28th			Brussel Sprouts
17	July 5th			Brussel Sprouts
16	July 12th
15	July 19th
14	July 26th
13	August 2nd
12	August 9th		beets
11	August 16th		beets
10	August 23rd		beets
9	August 30th		beets
8	Sept 6th		beets
7	Sept 13th
6	Sept 20th
5	Sept 27th
4	Oct 4th		garlic
3	Oct 11th		garlic
2	Oct 18nd		garlic
1	Oct 25th		garlic
0	Nov 1st		garlic

How to Use First and Last Frost Dates to Plan Your Seed Starting Schedule

Garden Almanac, Garden Planning

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-free growing season is around 170 days.

Last Frost Date (Cleveland, Ohio)

°F	90%	50%	10%
36°	Apr 25	May 11	May 27
32°	Apr 18	Apr 30	May 12
28°	Apr 4	Apr 16	Apr 29

First Frost Date (Cleveland, Ohio)

°F	10%	50%	90%
36°	Sep 25	Oct 7	Oct 18
32°	Oct 6	Oct 20	Nov 3
28°	Oct 23	Nov 4	Nov 15

*Data provided by the National Centers for Environmental Information.

Recent Last Frost Dates and Temperatures

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 30^th, and a 10% chance that the last frost will happen as late as May 15^th. 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 21^st,a low of 31 degrees on April 22^nd, and a light frost with a low of 37 on April 30^th. 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 9^th and 32 degrees on May 12^th
2019 – an amazingly early April 2^nd with a low of 32 degrees
2018 – April 29^th at 30 degrees.
2017 – April 8^th: 30 degrees.
2016 – April 10^th – 23 degrees.
2015 – April 24^th – 28 degrees.
2014 – April 15^th – 25 degrees
2013 – April 26^th – 30 degrees
2012 – April 29^th – 28 degrees
2011 – April 3^rd – 32 degrees
2010 – April 10^th – 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.