Start hardy Asian greens such as bok choy, mizuna and tatsoi outdoors around Indiana’s spring frost band, April 9 to April 21, and sow them again in late summer so they finish before the fall frost band of October 21 to October 30. Spring crops race the heat. Fall crops usually get the easier ride. The reasoning below shows how to set your own dates.
The short answer for Indiana
Indiana’s spring sowing window opens in the April 9 to April 21 band and runs until warm weather pushes the plants to bolt. Fall sowing runs from late summer, timed so the crop reaches harvest size before October 21 to October 30. Both bands come from the NOAA NCEI 1991-2020 Climate Normals for the Indianapolis station, and they describe 32°F freeze probabilities in a 30 to 70 percent band. They are odds of a freeze, not a guarantee that one will or won’t arrive.
Spring: the early edge is a bet
Purdue adds a caution worth taking seriously: roughly a 10% chance of a 32°F event remains after the published spring date. Seeds in the ground can sit through a late freeze, and hardy greens often shrug off a light one. Transplants on the early edge of the band are another matter, so keep a floating row cover or old bedsheets ready. If you want a reliable crop, the later part of the band is the safer bet. Sowing earlier is a gamble that pays off in some years and costs you a re-sow in others.
Fall: count backward from the frost band
Fall planning works in reverse. Take the days to maturity on the seed packet and subtract them from October 21. A packet that says 45 days points to a sowing around early September, and that is an example of the method, not a rule for every variety. Add a week or two, because growth slows as days shorten. The gap between the two frost bands is roughly half a year, about 26 to 29 weeks, so Indiana gives you room for both seasons. Only the fall sowing needs this backward arithmetic.
Which types suit these windows is a separate question, covered in The Best Asian Greens for Indiana. For the bigger picture of growing them here, see Growing Asian Greens in Indiana.
What will not work here
The calendar above leaves out a few plans that look sensible on paper and fail in practice.
Sowing on the earliest date and walking away
The April 9 edge of the band carries real freeze risk. Tender seedlings uncovered on a clear night in that window are the classic casualty. Treat the early date as a date to be ready, not a date to be confident.
Sowing in July and expecting a spring result
Greens planted in midsummer heat germinate poorly in hot soil and often bolt before they size up. A late-spring sowing has the same problem in reverse: the later it goes in after the frost band, the less time it has before warm weather ends the crop. Spring sowings that slip into May are the usual reason people decide Asian greens are “hard.” The plants were fine. The calendar was the problem.
Counting on the open bed through winter
The mean daily minimum of Indiana’s coldest month is 20.9°F (NOAA NCEI Climate Normals 1991-2020, Indianapolis reference). That is an average of the lows, so plenty of nights run colder. Hardy Asian greens take light frosts well. Sustained nights in the low 20s, with colder spells mixed in, will finish most of them in an uncovered bed. Plan fall crops as something you harvest before or just after the frost band, with a cover extending the season by a few weeks, not as winter vegetables.
Tight spacing in a humid summer
Indiana summers are humid, and crowded leafy plants hold moisture, which invites disease. Thin seedlings to the spacing on the packet, even if it feels wasteful. Watering once a week in a hot spell is a similar trap, since shallow-rooted greens dry out fast and turn bitter.
What changes across Indiana
Indiana does not have one climate. The USDA Plant Hardiness Zone Map (2023, built on 1991-2020 normals) places the state in 5b to 7a, which means there is no single zone and no single answer. The frost dates on this page use Indianapolis as the reference point. Southern Indiana runs earlier in spring and later in autumn than the north by a fortnight or more.
That fortnight matters in both directions. A gardener in the southern part of the state can reasonably move spring sowing earlier and push fall sowing later. A gardener in the northern part should do the opposite: wait longer in spring, and sow fall crops sooner, since the frost band arrives sooner there. The Indianapolis dates are the middle of the road, and the state is not a middle-of-the-road place.
One limit to keep in mind: a hardiness zone is built on a single variable, the average annual extreme minimum. It tells you whether a perennial survives winter. It does not set your sowing date, which depends on frost probabilities. Use the zone to understand your region, and the frost dates to schedule seed.
To find where you fall, look up your location on the USDA Plant Hardiness Zone Map instead of guessing from a neighbor’s advice. Garden centers and seed packets quote zones loosely, so the map is the reliable source.
Where to check this for your own county
A county recommendation beats a state one, and this page is the state one. For anything more precise, go to Purdue Extension, the land-grant university’s service, which has an office reaching every county in Indiana.
When you get there, look for two things. The first is the local planting calendar for your county, or the nearest one it publishes, because dates for a county near the Ohio River differ from those near Lake Michigan. The second is the list of varieties trialed in your county or close to it. Trial results tell you which cultivars held up through local heat, rain and disease, which a seed catalog cannot.
This page does not have a Purdue calendar written specifically for Asian greens, so it does not claim one. The calendar on hand from another state’s extension service covers a tall fescue lawn, which has nothing to do with these crops. The lesson is still useful: extension services usually publish by crop, not by state, so search for the vegetable or the leafy-greens category and check that the document matches what you are growing.
If your county office offers a Master Gardener helpline, it is a good source for how the last few springs have behaved locally. Bring your zip code and the crop you plan to sow.
Checking this against your own garden
Your garden’s own signals outrank every date on this page. Three are worth watching, and none needs a tool.
Soil warmth by feel. Push your hand a few inches into the bed in the morning. If the soil feels cold enough to ache, it is slow for germination. A bed that feels cool but not painful is ready for hardy greens. A south-facing bed beside a wall will warm days ahead of an open lawn corner, and that difference is your microclimate speaking.
The first male flowers on squash. Squash and cucumber plants produce male flowers first, and their arrival tells you warm-season conditions have settled in. For spring greens, that is a sign the cool window is closing, so stop sowing and start harvesting. If neighbors’ squash flower earlier than yours, your site runs cooler.
The first true leaves. The first pair after the seed leaves shows how fast a bed is moving. Note how many days it took from sowing, and keep that number for next year. Slow, pale or purple-tinged seedlings point to cold soil or a shaded spot, and a faster result than a friend’s garden down the road is worth knowing before you plan the fall sowing.
Common questions
Can I sow Asian greens in Indiana before the last frost?
Hardy types can be sown as the April 9 to April 21 band begins, but there is roughly a 10% chance of a 32°F freeze after the published date, so keep a cover ready. The earlier you sow, the more the outcome depends on that year’s weather.
When should I sow Asian greens for fall in Indiana?
Work backward from the October 21 to October 30 fall frost band, using the days to maturity on the packet and adding a week or two for shorter days. Use the Indianapolis dates as a reference and shift for your part of the state.
Do Indiana’s frost dates apply statewide?
They are Indianapolis dates. Southern Indiana runs earlier in spring and later in autumn than the north by a fortnight or more, so adjust accordingly.
Where can I find a county-level calendar?
Start with Purdue Extension and look for your county’s planting calendar and trialed varieties. A county source is more reliable than this state-level page.