Zone 6a Planting Calendar
In zone 6a, the median last spring frost falls around Apr 18 and the first fall frost around Oct 20, giving roughly 184 frost-free days. Average annual minimum temperature is -10°F to -5°F. Every date in the table below is calculated from those two frost dates.
Comparable areas: Chicago, IL, Columbus, OH, Denver, CO. Anchored on NWS 1991-2020 normals for Chicago O'Hare (last spring 32F April 21, first fall 32F October 19, ~181 frost-free days). Denver is also 6a but is a high-elevation continental site with a much shorter and more erratic frost-free window and frequent hard late-spring freezes - a clear illustration that a shared zone does not imply a shared frost calendar.
What to plant and when in zone 6a
Sorted by when you start each crop. Dates are calculated from a median last frost of Apr 18 and a first frost of Oct 20.
| Crop | Start indoors | Plant outside | Fall sowing | Harvest from |
|---|---|---|---|---|
| Celery | Jan 24 – Feb 7 | May 2 – May 15 | — | Aug 10 – Sep 9 |
| Leek | Jan 24 – Feb 21 | Mar 21 – Apr 3 | — | Jun 19 – Aug 18 |
| Onion | Jan 24 – Feb 7 | Mar 28 – Apr 10 | — | Jul 6 – Jul 26 |
| Rosemary | Jan 24 – Feb 7 | May 2 – May 15 | — | Jul 21 – Aug 10 |
| Kale | Jan 31 – Feb 21 | Mar 21 – Apr 3 | Jul 28 – Aug 10 | May 10 – Jun 11 |
| Broccoli | Feb 7 – Feb 28 | Mar 28 – Apr 10 | Jul 21 – Aug 3 | May 17 – Jun 26 |
| Cabbage | Feb 7 – Feb 28 | Mar 28 – Apr 10 | Jul 21 – Aug 3 | May 27 – Jul 6 |
| Pepper (sweet/bell) | Feb 7 – Mar 7 | May 9 – May 22 | — | Jul 18 – Aug 2 |
| Chives | Feb 7 – Feb 21 | Apr 18 – May 1 | — | Jul 7 – Jul 17 |
| Common Thyme | Feb 7 – Feb 21 | Apr 18 – May 1 | — | Jun 17 – Jul 17 |
| Greek Oregano | Feb 7 – Feb 21 | Apr 18 – May 1 | — | Jul 7 – Jul 17 |
| Cauliflower | Feb 14 – Mar 7 | Apr 4 – Apr 17 | Jul 21 – Aug 3 | May 24 – Jun 23 |
| Eggplant | Feb 21 – Mar 7 | May 2 – May 15 | — | Jun 26 – Jul 21 |
| Sweet Potato | Feb 21 – Mar 7 | May 9 – May 22 | — | Aug 7 – Sep 6 |
| Basil | Feb 21 – Mar 7 | Apr 25 – May 8 | — | Jul 1 – Jul 31 |
| Garden Sage | Feb 21 – Mar 7 | Apr 18 – May 1 | — | Jun 27 – Jul 7 |
| Parsley | Feb 21 – Mar 7 | Apr 18 – May 1 | Aug 11 – Aug 24 | Jun 27 – Jul 7 |
| Spearmint | Feb 21 – Mar 7 | Apr 18 – May 1 | — | Jun 17 – Jul 17 |
| Calendula / Pot Marigold | Feb 21 – Mar 7 | Apr 4 – Apr 17 | Aug 25 – Sep 7 | May 24 – Jun 3 |
| French Marigold | Feb 21 – Mar 21 | Apr 25 – May 8 | — | Jun 9 – Jun 24 |
| Sweet Alyssum | Feb 21 – Mar 7 | Apr 4 – Apr 17 | Aug 25 – Sep 7 | May 16 – May 30 |
| Tomato | Feb 28 – Mar 14 | Apr 25 – May 8 | — | Jun 19 – Jul 24 |
| Bok Choy | Mar 7 – Mar 21 | Apr 4 – Apr 17 | Aug 25 – Sep 7 | May 4 – Jun 3 |
| Collard Greens | Mar 7 – Mar 21 | Apr 4 – Apr 17 | Jul 28 – Aug 10 | Jun 3 – Jun 23 |
| Kohlrabi | Mar 7 – Mar 21 | Mar 28 – Apr 10 | Aug 18 – Aug 31 | May 24 – Jun 3 |
| Lettuce | Mar 7 – Mar 21 | Mar 28 – Apr 10 | Aug 11 – Aug 24 | May 24 – Jun 13 |
| Spinach | Mar 7 – Mar 14 | Mar 28 – Apr 10 | Sep 1 – Sep 14 | May 25 – Jun 5 |
| Swiss Chard | Mar 7 – Mar 21 | Apr 4 – Apr 17 | Sep 22 – Oct 5 | May 14 – May 29 |
| Pea | — | Mar 14 – Mar 27 | Aug 18 – Aug 31 | May 8 – May 28 |
| Rhubarb | — | Mar 14 – Mar 27 | — | Mar 13 |
| Watermelon | Mar 14 – Apr 4 | May 2 – May 15 | — | Jul 11 – Aug 5 |
| Arugula | — | Mar 21 – Apr 3 | Sep 8 – Sep 21 | Apr 20 – May 10 |
| Asparagus | — | Mar 21 – Apr 3 | — | Mar 20 |
| Cucumber | Mar 21 – Apr 4 | May 2 – May 15 | — | Jun 21 – Jul 11 |
| Pumpkin | Mar 21 – Mar 28 | May 2 – May 15 | — | Jul 26 – Aug 30 |
| Turnip | — | Mar 21 – Apr 3 | Aug 18 – Aug 31 | Apr 30 – Jun 4 |
| Nasturtium | Mar 21 – Mar 28 | Apr 25 – May 8 | — | Jun 19 – Jun 29 |
| Beet | — | Mar 28 – Apr 10 | Aug 11 – Aug 24 | May 17 – Jun 6 |
| Carrot | — | Mar 28 – Apr 10 | Aug 4 – Aug 17 | May 27 – Jun 16 |
| Potato | — | Mar 28 – Apr 10 | — | Jun 6 – Jul 26 |
| Radish | — | Mar 28 – Apr 10 | Sep 8 – Sep 21 | Apr 18 – May 12 |
| Sunflower | Mar 28 – Apr 4 | Apr 25 – May 8 | — | Jul 4 – Aug 3 |
| Parsnip | — | Apr 4 – Apr 17 | — | Jul 23 – Aug 12 |
| Winter Squash (Butternut) | Apr 4 – Apr 11 | May 2 – May 15 | — | Jul 21 – Aug 10 |
| Cantaloupe (Muskmelon) | Apr 4 – Apr 11 | May 2 – May 15 | — | Jul 9 – Jul 26 |
| Strawberry | — | Apr 4 – Apr 17 | — | May 2 – May 4 |
| Dill | — | Apr 11 – Apr 24 | Aug 11 – Aug 24 | May 21 – Jun 5 |
| Bush bean | — | Apr 18 – May 1 | Aug 11 – Aug 24 | Jun 7 – Jun 17 |
| Pole bean | — | Apr 18 – May 1 | — | Jun 15 – Jun 20 |
| Sweet corn | — | Apr 18 – May 1 | — | Jun 17 – Jul 27 |
| Borage | — | Apr 18 – May 1 | — | Jun 7 – Jun 17 |
| Cilantro / Coriander | — | Apr 18 – May 1 | Aug 25 – Sep 7 | Jun 2 – Jun 27 |
| Summer squash / zucchini | — | Apr 25 – May 8 | — | May 30 – Jun 19 |
| Okra | — | May 2 – May 15 | — | Jul 1 – Jul 11 |
| Brussels Sprouts | — | Jun 27 – Jul 10 | Jul 14 – Jul 27 | Sep 20 – Oct 15 |
| Garlic | — | — | Oct 20 – Nov 2 | — |
Print this page for a calendar you can pin up in the shed.
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One zone is not one climate. USDA hardiness zones are drawn from average winter minimum temperature and nothing else, so they do not determine frost dates. Two gardens in zone 6a can differ by two or three weeks depending on elevation, distance from water, and local topography. Treat this page as a starting schedule and adjust it to what your own garden has actually done. How these dates were derived →
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