When to Plant Tulips

The rule: wait for cool soil, finish before hard freeze

Tulips are planted in fall, not spring, because the bulbs need a long cold period in the ground before they can flower. The trigger for planting is soil temperature rather than the calendar. Rutgers and Nebraska Extension both say to plant once the soil falls below 60°F; Wisconsin Extension suggests waiting until it is around 50 to 55°F.

Bulbs then need several weeks to grow roots before the ground freezes. South Dakota State asks for 4 to 6 weeks of rooting time; Illinois Extension sets its target at 4 to 6 weeks before freeze-up as well. Put together, the practical window runs from about six weeks before your average first fall frost to about two weeks after it. The dates for your zone above are calculated from that rule and your local frost records.

If you have a soil thermometer, check at planting depth, 6 to 8 inches down. Without one, South Dakota State’s rule of thumb works well: start when nighttime temperatures settle into the 40s and low 50s °F.

Typical timing by region

• Upper Midwest, northern Plains and mountain West (zones 3-5): mid-September to mid-October in South Dakota, where the extension service says the sooner the better. Oregon State plants from late September through October in cold central and eastern Oregon.
• Mid-Atlantic, Ohio Valley and lower Midwest (zones 6-7): Rutgers gives mid-September through October for New Jersey, Penn State September to October for western Pennsylvania, and Illinois Extension mid-October to early November for central Illinois.
• Upper South (zones 7-8): Clemson waits until the soil at planting depth stays below 60°F, which in the upper Piedmont of South Carolina is usually late October or November. Many gardeners here chill bulbs anyway, because winters are too short for reliable bloom.
• Coastal South, Florida, south Texas and mild-winter California (zones 8b-10): winters are too mild to chill bulbs in the ground. Refrigerate them first (UF/IFAS asks for two to four months, Texas A&M AgriLife in San Antonio 45 to 60 days, UC Master Gardeners in Solano County at least 6 to 8 weeks), then plant in late November or December. Clemson gives November to late December for refrigerated bulbs in central and coastal South Carolina. Plant them as soon as they come out of the cold.

Planting too early or too late

Too early. Warm soil pushes bulbs into growth before winter. For a related reason, Oregon State Extension tells Central Oregon gardeners to avoid south-facing foundations, where warm soil triggers premature growth that frost can damage. Buy bulbs when selection is good, but store them somewhere cool and dry, about 60 to 65°F (Nebraska), until the soil cools. Keep them away from ripening fruit, which gives off ethylene that damages the flower bud.

Too late. Iowa State notes tulips can go in as late as late November or early December if the ground is not frozen. As long as you can dig, plant: a bulb in cold ground is far more likely to flower than one left in a bag all winter, as Illinois Extension puts it. After a late planting, water the bed and spread 2 to 3 inches of mulch to slow freezing and give roots a little more time.

Missed it entirely? Bulbs that sat unplanted all winter have missed their chill. If they are still firm, plant them as soon as the ground can be worked, but expect short-stemmed flowers or none in the first spring; Clemson notes that under-chilled bulbs bloom close to the ground on very short stems.

Timing pots and forced tulips

For outdoor containers, plant at the same time as garden bulbs.

To force tulips for indoor bloom, pot them in October or November and hold them at 35 to 48°F for at least 12 to 13 weeks (Rutgers, Nebraska). Count back from when you want flowers: after chilling, they bloom in about three to four weeks in a bright, cool room, so pots started in mid-October can flower around mid-February.

When tulips bloom

Fall-planted tulips flower from mid to late spring. In South Dakota, peak bloom comes between late April and mid-May, and South Dakota State notes that tulips by a warm building wall open first. Iowa State notes that Fosteriana tulips open early in spring and Darwin hybrids in midseason. Planting a mix of classes stretches the season.