Maryland gardeners get two sowing windows for turnips each year, not one. The spring window opens as soil dries out in mid-March and the fall window opens in late July, and which one produces the better root depends on what the Maryland calendar actually measures.
The short answer for Maryland
Turnips are a cool-season crop, and Maryland’s frost dates set both ends of the calendar. The state’s last spring frost falls between April 3 and April 16, and the first fall frost lands between October 26 and November 5, according to NOAA’s 1991-2020 climate normals for the 30-70% probability band. That’s a probability of freezing temperatures, not a guarantee, which matters because turnip seedlings tolerate a light frost once they have true leaves.
Working from those two anchor dates gives a spring window and a fall window. In spring, turnip seed can go into the ground roughly three weeks ahead of the last frost date, since germination only needs the soil to climb into the 40s. That puts spring sowing somewhere between mid-March and the first days of April for most of the state. Roots from that sowing mature before summer heat turns them woody and bitter.
The fall window is the one Maryland growers lean on more, because turnips actually improve with a touch of cold before harvest. Counting back from the October 26 to November 5 frost window, and allowing turnip roots the 40 to 60 days most varieties need to size up, the fall sowing window runs from late July through the first week of September. Sow earlier in that range if you want mature roots, later if you’re growing turnip greens, which are ready in half the time.
Neither window is fixed to a single day, and that’s the point. A frost date from a 30-year climate average tells you when freezing is likely, not when it will happen this particular year. Treat the dates above as the center of a range, not a deadline.
What’s missing from this page, and worth saying plainly: nothing in the available data pins these windows to a specific soil temperature reading for Maryland, so the ranges above come from the frost dates and standard turnip maturity windows, not from a local soil-temperature study.
What will not work here
Rutabaga is the first casualty of Maryland’s calendar, and it’s a timing problem, not a hardiness one. Rutabaga needs 90 days or more to size up, well beyond the turnip’s 40 to 60. Sow it at the same time as a fall turnip crop, in early August, and you’re asking it to finish by early November, right against the first fall frost of October 26 to November 5. There’s no cushion left for a slow week of weather. Rutabaga sown after mid-July in most of Maryland runs out of season before the roots reach a usable size.
Summer sowing is the second trap, and it catches people trying to bridge the gap between spring and fall crops. Maryland summers push well past turnip germination’s comfort zone, and dry topsoil in July kills a seed bed faster than most people expect. A turnip seed sown a half-inch deep in cracked, hot soil either fails to sprout or comes up so weak it bolts to flower within weeks instead of building a root. Watering once a week doesn’t fix this. Turnip seed beds in Maryland’s mid-summer heat need moisture held at the surface daily until germination, which is why most local guidance treats June and early July as a dead zone for turnip seed, not a shoulder season.
Tight spacing is the third failure point, and it’s a humidity problem specific to a state where summer air holds onto moisture for weeks at a stretch. Turnip foliage planted at close spacing traps that moisture at leaf level, and fungal leaf spot moves through a dense stand fast. The fix isn’t a fungicide schedule, it’s air movement between plants from the start, which matters more here than it would in a drier climate where the same spacing causes no trouble at all.
Finally, an early spring gamble backfires more often than gardeners expect. Sowing weeks ahead of the mid-March opening, into cold wet soil, doesn’t get you an earlier crop. It gets you rotted seed, because turnip seed sitting in soil below the 40s simply sits there decaying instead of germinating.
What changes across Maryland
Maryland’s USDA hardiness zone range runs from 5b to 8a, and that spread alone tells you this state has no single sowing calendar. The USDA map is built on one number, the average annual extreme minimum temperature, and a jump from zone 5b to zone 8a is a difference of roughly 15 degrees on that measure. Baltimore sits inside that range as the reference point for the frost dates used above, but it does not represent the whole state.
Western Maryland, Garrett and Allegany counties in particular, is mountainous terrain that runs weeks behind the rest of the state on both ends of the season. Spring arrives later there and fall frost arrives earlier, which shortens the whole growing window from both directions at once. A gardener working that terrain should expect to shift the entire sowing calendar back by two to three weeks in spring and pull the fall sowing date forward by the same margin, since the frost-free stretch in between is genuinely shorter.
The Eastern Shore runs the opposite way. Milder winters and a longer buffer before the first fall frost mean gardeners there can push the spring sowing date earlier and stretch the fall sowing window later into September without the same risk of running out of season. That’s the advantage of growing in the warmer end of a 5b-8a spread instead of the colder end.
None of this tells an individual reader which zone applies to their own yard, and it shouldn’t. Hardiness zones shift with elevation and local terrain in ways a state-level map can’t resolve. The USDA Plant Hardiness Zone Map, built on the 1991-2020 normals, is the tool for finding that answer at the address level, and it’s worth checking before locking in a date from any state-wide calendar, including this one.
Where to check this for your own county
Everything above is a state average, and Maryland is large enough that a county recommendation will beat it every time. The University of Maryland Extension, the state’s land-grant extension service, publishes exactly that kind of local detail at extension.umd.edu, and it’s the next stop for anyone trying to tighten these dates to their own address.
Two things are worth pulling from that site specifically. The first is a county-level or regional planting calendar, which will reflect microclimate differences, coastal versus inland, mountain versus valley, that a statewide frost-date range can’t capture. The second is any list of turnip and rutabaga varieties that extension agents have actually trialed in Maryland conditions, since variety performance shifts with humidity and season length in ways a seed packet’s national averages won’t show.
This page works from statewide frost data because that’s the level at which the source data exists. A county extension office works from field trials and local grower reports, which is a finer grain of information than any climate normal can provide. When the two disagree, defer to the county source, not this one.
It’s also worth checking whether your county extension office runs a soil testing program, since turnips are sensitive to soil pH and boron deficiency in ways that show up as hollow or cracked roots, a problem no sowing date will fix on its own.
The Moon calendar is a separate, older custom: see when to plant turnips by the moon, written as tradition rather than fact.
Checking this against your own garden
Every date on this page is a starting estimate, and your own garden will correct it faster than any calendar can. Three signals matter more than the calendar once seed is in the ground.
Soil warmth by feel comes first. Push a finger two inches into the bed before sowing. Cold and sticky soil means germination will stall no matter what the calendar says; crumbly soil that’s lost its winter chill means the spring window has genuinely opened in your yard, regardless of what date it is on the wall calendar.
First true leaves are the second signal. The rounded seed leaves that appear first don’t tell you much, but the jagged true leaves that follow, usually within a week or two, confirm the seedling has moved past its most vulnerable stage. If true leaves are slow to show up, the soil was likely still too cold when you sowed, and that’s useful information for next year’s timing in that same bed.
The third signal is an early flowering stalk, which in turnips almost always means bolting, not maturity. A turnip that throws a flower stalk within a few weeks of sowing is responding to heat stress or a cold snap right after germination, and it’s telling you that particular sowing date didn’t suit your yard’s microclimate this year. Note the date the flower stalk appears and shift next season’s sowing a week or two away from it, in whichever direction the stress came from. That single observation, repeated over a season or two, will outperform any statewide date range for your specific patch of ground.