Sue from Ohio recently requested that I post a time line for my seed starting dates. What a great idea! Knowing when to plant each vegetable is often difficult to determine, but it’s key to success. And it just happens to be one of the things I talked about last spring when I put on my Master Gardener hat at our Spring Demo Day event. So I dusted off the notes from my talk and tweaked them a bit for the following.
Let me say right up front that all the date ranges I am going to throw out here are for gardeners with climates similar to our own USDA zone 6B, and with a similar length growing season. For example, here in southern Indiana there is less than a 10% chance of having a frost after the last week of April. If you wait until May 1st, there is pretty much a zero chance of frost. In fall our first frost usually occurs around the last week of October. So that gives us around 180 frost free growing days each year.
Many state universities have free gardening resources available online, and I urge people to use them – it’s your tax dollars at work! Purdue University has a publication called Indiana Vegetable Planting Calender (HO-186W) that I use to develop my own planting schedule. Ohio has some good ones too, and you can find links to many of them on this web page.
In the table that follows ‘sow’ refers to direct seeding outdoors, and is usually done for peas, carrot, corn, radish, spinach, beans, and turnip. ‘Start’ means starting seeds indoors in pots, soil blocks, flats, trays or cell packs, and is usually done for broccoli, cabbage, cauliflower, tomato, pepper and eggplant. Things like beet, Swiss chard, lettuce, arugula, endive, kohlrabi, kale, squash, melons, pumpkin, cucumber and many of the Asian greens can either be direct seeded outdoors -or- started inside. I often start these vegetables inside under lights to get a jump on the growing season. ‘Plant’ means to plant transplants outside or to directly plant things like onion sets, sweet potato slips or seed potato pieces.
- Start broccoli, cabbage, cauliflower, Florence fennel, kale, kohlrabi, lettuce, parsley
- Sow arugula, mache, spinach
- Sow peas, radish, spinach, arugula, endive
- Plant onion(sets or transplants)
- Start lettuce, pak choi, early tomatoes
- Start eggplant, tomato, pepper
- Sow beet, carrot, chard, lettuce, radish, turnip
- Plant broccoli, cabbage, cauliflower, chard, Florence fennel, kale, kohlrabi, lettuce, onion, potato
- Start lettuce
- Sow beet, carrot, chard, lettuce
- Plant broccoli, chard, Florence fennel, kohlrabi, lettuce, onion, potato
- Sow green bean
- Start cucumber, melon, pumpkins, squash
- Plant lettuce
- Sow corn, cucumbers, green bean, melons, pumpkin, squash
- Plant cucumber, lettuce, melon, pumpkin, squash, tomato
- Plant pepper, eggplant, okra
- Plant sweet potato
- Start fall broccoli, cabbage, cauliflower, collard greens, kale
LATE JULY/EARLY AUGUST
- Sow beans (snap), beets, carrot, chard, peas, turnip, kohlrabi
- Plant fall broccoli, cabbage, cauliflower, collard greens, kale, kohlrabi
MID AUGUST-LATE SEPTEMBER
- Sow arugula, Asian greens, endive, lettuce, mache, radish, spinach
- Plant Asian greens, endive, lettuce
LATE OCTOBER/EARLY NOVEMBER
- plant garlic
I have to emphasize that the above dates for sowing and planting are guidelines only! Last year was a great example. We had record rains, and a cool wet spring, which made it difficult to get the soil prepared. It also made the ground slower to warm up. Another way to decide when to plant certain vegetables is to use soil temperature.
You can find soil thermometers at many garden centers, but you can use any type thermometer as long as it registers in the necessary range. Take the soil temperature by inserting the thermometer in the soil where you intend to plant the specific crop. An instant read thermometer is also good to monitor the temperature of your seed starting mix. Following is a table listing the minimum soil temperatures preferred by certain vegetables. Seed packets and catalogs are a good source of information regarding germination temperatures (Johnny’s Selected Seeds is one of my favorite sources).
- 45°F – potato, onion, peas, spinach, arugula, lettuce
- 50°F – broccoli, cabbage, cauliflower
- 60°F – tomato, corn, beet
- 65°F – cantaloupe, cucumber, green bean, pepper, pumpkin, squash
- 70°F – lima bean, okra
For instance, if you plant your tomatoes when the soil is below 60°F, they’re just going to sit there and sulk. If you plant seeds when the soil is too cold, they are likely to rot. Some seeds (like lettuce and spinach) won’t germinate when the soil is too hot. Of course there are ways to warm up soil faster in spring, like using black plastic or raised beds, but that’s a subject for another article! I also plan on doing a few more posts in the near future regarding some of the specifics about my seed starting techniques, including soil mixes, lights, heating mats, and so on. So stay tuned if you are interested!
Ultimately, I use a combination of the calendar, soil thermometer and the weather report when making the decision of when to plant. My above lists don’t include all vegetables by any means, but do include most of the ones I grow regularly. I hope this information will be helpful. If anyone has any questions, I’m always happy to try and answer them.
I can see it is time for me be starting some seeds of the cabbage family here ASAP, along with some petunias and parsley. So I better break out the seeds and soil mix and get growing!
For more about growing plants from seed, see my page on Seed Starting Information.
For more information about specific fruits and vegetables, see Variety Spotlights.