Frost Dates for Rockville, MD 20851
Rockville has 4 ZIP codes. The Rockville, MD frost page lists all of them with their dates.
Last spring frost April 16 · First fall frost October 22 · 189 frost-free days · USDA Zone 7b
ZIP 20851 has about 14,900 people, one of 4 ZIP codes in Rockville.
Long season: 189 frost-free days. Spring frost risk spans March 27–May 4 (38 days). Fall frost risk spans October 6–November 8 (33 days).
Frost probability for 20851
| Frost | 10% | 50% | 90% |
|---|---|---|---|
| Spring (last frost) | May 4 | April 16 | March 27 |
| Fall (first frost) | October 6 | October 22 | November 8 |
Dates come from NOAA 1971–2000 freeze probabilities at ROCKVILLE 1 NE (3.5 km away); the 50% date is the median year.
Which crops fit a 189-day season in Rockville
In Rockville (189 frost-free days, a long season), 30 of 56 planner crops fit outright, 25 get two plantings, 1 crop is perennial.
| Crop | Start indoors | Plant out / sow | Days you have | Verdict | Last sow date |
|---|---|---|---|---|---|
| Tomato | Mar 12 | Apr 30–May 7 | 147 | fits: 80 days to maturity, 147 available after Apr 30. | Jun 22 |
| Pepper | Mar 5 | Apr 30–May 7 | 147 | fits: 75 days to maturity, 147 available after Apr 30. | Jun 27 |
| Lettuce | Feb 19 | Mar 19–Mar 26 | 224 | two-plantings: Plant Mar 19 and again by Aug 31; both mature before Oct 29. | Aug 31 |
| Carrots | — | Mar 26–Apr 2 | 231 | fits: 70 days to maturity, 231 available after Mar 26. | Aug 20 |
| Cucumber | Mar 26 | Apr 30–May 7 | 161 | two-plantings: Plant Apr 30 and again by Jul 26; both mature before Oct 8. | Jul 26 |
| Beans | — | Apr 23–May 7 | 175 | two-plantings: Plant Apr 23 and again by Aug 2; both mature before Oct 15. | Aug 2 |
| Peas | — | Feb 19–Apr 30 | 252 | fits: 65 days to maturity, 252 available after Feb 19. | Aug 11 |
| Zucchini | Apr 2 | Apr 30–May 7 | 161 | two-plantings: Plant Apr 30 and again by Jul 31; both mature before Oct 8. | Jul 31 |
| Onion | Jan 22 | Mar 19–Apr 2 | 224 | fits: 100 days to maturity, 224 available after Mar 19. | — |
| Spinach | — | Feb 19–Apr 9 | 266 | two-plantings: Plant Feb 19 and again by Sep 19; both mature before Nov 12. | Sep 19 |
| Kale | Feb 5 | Mar 19–Apr 2 | 238 | two-plantings: Plant Mar 19 and again by Sep 4; both mature before Nov 12. | Sep 4 |
| Broccoli | Feb 19 | Mar 19–Apr 2 | 224 | fits: 80 days to maturity, 224 available after Mar 19. | Jul 27 |
| Cabbage | Feb 19 | Mar 19–Apr 2 | 238 | fits: 70 days to maturity, 238 available after Mar 19. | Aug 20 |
| Radish | — | Feb 19–May 14 | 252 | two-plantings: Plant Feb 19 and again by Sep 20; both mature before Oct 29. | Sep 20 |
| Beets | — | Feb 19–May 14 | 252 | two-plantings: Plant Feb 19 and again by Aug 21; both mature before Oct 29. | Aug 21 |
| Potatoes | — | Apr 2–Apr 9 | 210 | fits: 90 days to maturity, 210 available after Apr 2. | — |
| Garlic | — | Oct 22 | 294 | overwinter: Plant Oct 22 to Nov 12; harvest the following summer. | Nov 12 |
| Strawberry | — | Mar 12–May 7 | 245 | perennial: A perennial: plant Mar 12; it fruits from the following year and keeps producing for several years. | — |
| Corn | Mar 19 | Apr 23–Apr 30 | 161 | fits: 75 days to maturity, 161 available after Apr 23. | Jul 4 |
| Pumpkin | Apr 2 | Apr 30–Apr 30 | 154 | fits: 100 days to maturity, 154 available after Apr 30. | Jun 9 |
| Cauliflower | Mar 5 | Apr 9–Apr 23 | 203 | fits: 75 days to maturity, 203 available after Apr 9. | Aug 1 |
| Swiss Chard | Feb 19 | Apr 2–Apr 2 | 210 | two-plantings: Plant Apr 2 and again by Aug 21; both mature before Oct 29. | Aug 21 |
| Arugula | — | Feb 19–May 14 | 266 | two-plantings: Plant Feb 19 and again by Sep 19; both mature before Nov 12. | Sep 19 |
| Brussel Sprouts | Feb 19 | Mar 19–Apr 2 | 238 | fits: 100 days to maturity, 238 available after Mar 19. | Jul 21 |
| Butternut Squash | Apr 2 | Apr 30–May 7 | 154 | fits: 100 days to maturity, 154 available after Apr 30. | Jun 9 |
| Eggplant | Feb 26 | Apr 30–May 7 | 147 | fits: 70 days to maturity, 147 available after Apr 30. | Jul 2 |
| Okra | Mar 19 | Apr 23–Apr 30 | 168 | two-plantings: Plant Apr 23 and again by Jul 31; both mature before Oct 8. | Jul 31 |
| Basil | Mar 12 | May 7–May 7 | 154 | two-plantings: Plant May 7 and again by Jul 26; both mature before Oct 8. | Jul 26 |
| Cilantro | — | Mar 19–Apr 9 | 224 | two-plantings: Plant Mar 19 and again by Aug 26; both mature before Oct 29. | Aug 26 |
| Parsley | Feb 5 | Apr 23–Apr 30 | 189 | fits: 70 days to maturity, 189 available after Apr 23. | Aug 6 |
| Celery | Feb 5 | Apr 23–May 7 | 189 | fits: 120 days to maturity, 189 available after Apr 23. | Jun 17 |
| Scallions | Feb 5 | Mar 19–Apr 2 | 238 | two-plantings: Plant Mar 19 and again by Aug 30; both mature before Nov 12. | Aug 30 |
| Turnip | — | Mar 19–Apr 2 | 238 | two-plantings: Plant Mar 19 and again by Sep 9; both mature before Nov 12. | Sep 9 |
| Kohlrabi | — | Mar 5–Mar 19 | 252 | two-plantings: Plant Mar 5 and again by Sep 4; both mature before Nov 12. | Sep 4 |
| Bok Choy | Mar 19 | Apr 9–Apr 16 | 203 | two-plantings: Plant Apr 9 and again by Aug 31; both mature before Oct 29. | Aug 31 |
| Collards | Feb 5 | Mar 19–Apr 2 | 238 | two-plantings: Plant Mar 19 and again by Aug 30; both mature before Nov 12. | Aug 30 |
| Cantaloupe | Apr 2 | Apr 30–May 7 | 147 | fits: 85 days to maturity, 147 available after Apr 30. | Jun 17 |
| Chives | Jan 22 | Apr 23–Apr 30 | 203 | fits: 90 days to maturity, 203 available after Apr 23. | — |
| Dill | — | Feb 19–May 14 | 252 | two-plantings: Plant Feb 19 and again by Aug 21; both mature before Oct 29. | Aug 21 |
| Oregano | Feb 5 | Apr 23–Apr 30 | 203 | fits: 80 days to maturity, 203 available after Apr 23. | — |
| Rosemary | Jan 22 | Apr 23–Apr 30 | 189 | fits: 80 days to maturity, 189 available after Apr 23. | — |
| Sage | Feb 19 | Apr 23–Apr 30 | 203 | fits: 75 days to maturity, 203 available after Apr 23. | — |
| Thyme | Feb 5 | Apr 23–Apr 30 | 203 | fits: 90 days to maturity, 203 available after Apr 23. | — |
| Calendula | Mar 5 | Apr 2–Apr 16 | 210 | two-plantings: Plant Apr 2 and again by Aug 26; both mature before Oct 29. | Aug 26 |
| Cosmos | Mar 19 | Apr 16–Apr 30 | 175 | two-plantings: Plant Apr 16 and again by Jul 26; both mature before Oct 8. | Jul 26 |
| Lavender | Jan 22 | Apr 16–Apr 30 | 210 | fits: 90 days to maturity, 210 available after Apr 16. | — |
| Marigolds | Mar 5 | Apr 16–Apr 23 | 175 | two-plantings: Plant Apr 16 and again by Aug 5; both mature before Oct 8. | Aug 5 |
| Melons | Apr 2 | Apr 30–May 7 | 147 | fits: 85 days to maturity, 147 available after Apr 30. | Jun 17 |
| Mint | — | Apr 16–Apr 30 | 210 | fits: 90 days to maturity, 210 available after Apr 16. | — |
| Nasturtiums | Mar 19 | Apr 16–Apr 23 | 175 | two-plantings: Plant Apr 16 and again by Jul 31; both mature before Oct 8. | Jul 31 |
| Pole Beans | — | Apr 23–May 7 | 168 | fits: 65 days to maturity, 168 available after Apr 23. | Jul 21 |
| Spaghetti Squash | Apr 2 | Apr 30–May 7 | 154 | fits: 90 days to maturity, 154 available after Apr 30. | Jun 19 |
| Sunflowers | — | Apr 16–Apr 30 | 175 | fits: 70 days to maturity, 175 available after Apr 16. | Jul 16 |
| Tomatillos | Feb 19 | Apr 23–Apr 30 | 154 | fits: 75 days to maturity, 154 available after Apr 23. | Jun 27 |
| Watermelon | Apr 2 | Apr 23–Apr 30 | 154 | fits: 80 days to maturity, 154 available after Apr 23. | Jun 22 |
| Yellow Squash | Apr 2 | Apr 30–May 7 | 161 | two-plantings: Plant Apr 30 and again by Jul 31; both mature before Oct 8. | Jul 31 |
| Zinnias | Mar 19 | Apr 16–Apr 30 | 175 | two-plantings: Plant Apr 16 and again by Jul 26; both mature before Oct 8. | Jul 26 |
Month by month in Rockville
| Month | What to do |
|---|---|
| January | Start indoors: Chives (Jan 22), Lavender (Jan 22), Onion (Jan 22), Rosemary (Jan 22). |
| February | Start indoors: Celery (Feb 5), Collards (Feb 5), Kale (Feb 5), Oregano (Feb 5), Parsley (Feb 5), Scallions (Feb 5), +9 more. Direct sow from: Arugula (Feb 19), Beets (Feb 19), Dill (Feb 19), Peas (Feb 19), Radish (Feb 19), Spinach (Feb 19). |
| March | Start indoors: Calendula (Mar 5), Cauliflower (Mar 5), Marigolds (Mar 5), Pepper (Mar 5), Basil (Mar 12), Tomato (Mar 12), +7 more. Direct sow from: Kohlrabi (Mar 5), Cilantro (Mar 19), Turnip (Mar 19), Carrots (Mar 26). Transplant from: Broccoli (Mar 19), Brussel Sprouts (Mar 19), Cabbage (Mar 19), Collards (Mar 19), Kale (Mar 19), Lettuce (Mar 19), +2 more. Plant: Strawberry (Mar 12). |
| April | Start indoors: Butternut Squash (Apr 2), Cantaloupe (Apr 2), Melons (Apr 2), Pumpkin (Apr 2), Spaghetti Squash (Apr 2), Watermelon (Apr 2), +2 more. Direct sow from: Potatoes (Apr 2), Sunflowers (Apr 16), Beans (Apr 23), Pole Beans (Apr 23). Transplant from: Calendula (Apr 2), Swiss Chard (Apr 2), Bok Choy (Apr 9), Cauliflower (Apr 9), Cosmos (Apr 16), Lavender (Apr 16), +26 more. Last frost around April 16. |
| May | Transplant from: Basil (May 7). |
| June | Last sowing dates: Butternut Squash (Jun 9), Pumpkin (Jun 9), Cantaloupe (Jun 17), Celery (Jun 17), Melons (Jun 17), Spaghetti Squash (Jun 19), +4 more. |
| July | Last sowing dates: Eggplant (Jul 2), Corn (Jul 4), Sunflowers (Jul 16), Brussel Sprouts (Jul 21), Pole Beans (Jul 21), Basil (Jul 26), +8 more. |
| August | Last sowing dates: Cauliflower (Aug 1), Beans (Aug 2), Marigolds (Aug 5), Parsley (Aug 6), Peas (Aug 11), Cabbage (Aug 20), +10 more. |
| September | Last sowing dates: Kale (Sep 4), Kohlrabi (Sep 4), Turnip (Sep 9), Arugula (Sep 19), Spinach (Sep 19), Radish (Sep 20). |
| October | Direct sow from: Garlic (Oct 22). First frost around October 22. |
| November | Last sowing dates: Garlic (Nov 12). |
| December | Clean up spent plants. Add compost to beds. Rest, review, and plan next year's garden. |
Frequently Asked Questions
What is the last frost date for Rockville, MD (ZIP 20851)?
The median last spring frost date for Rockville, MD (ZIP code 20851) is around April 16. This is the 50th-percentile date — meaning half of all years see frost end before this date. Use the 10% and 90% dates to understand the full range of risk in your area. One year in ten frost ends before March 27; one in ten it runs past May 4.
What is the first fall frost date in Rockville, MD?
The median first fall frost date for Rockville, MD is around October 22. Plan to harvest or protect frost-sensitive crops like tomatoes and peppers at least a week before this date to avoid losses. The first frost arrives around October 6 in the earliest one-in-ten years, so cover tomatoes and peppers from then.
How long is the growing season in Rockville, MD?
The frost-free growing season in Rockville is about 189 days. This window — from your last spring frost to your first fall frost — is when warm-season vegetables thrive. Cold-hardy crops like kale, spinach, and peas can extend your season by weeks on either side. In Rockville (189 frost-free days, a long season), 30 of 56 planner crops fit outright, 25 get two plantings, 1 crop is perennial.
What USDA hardiness zone is Rockville, MD?
Rockville, MD is in USDA hardiness zone 7b (2023 USDA Plant Hardiness Zone Map). Zones come from the average coldest winter temperature, so they tell you which perennials survive the winter; the frost dates on this page tell you when to plant.
When should I start tomatoes indoors in Rockville, MD?
Start tomatoes indoors Mar 12 and plant out Apr 30 in Rockville. The planner uses the local median last frost and this crop's indoor-start and transplant offsets.
How many plantings of lettuce fit in Rockville?
Two: plant Mar 19 and again by Aug 31; both mature before Oct 29.
When do I plant garlic in Rockville?
Oct 22 to Nov 12; it overwinters and is ready the following summer.
Can I get two tomato crops in Rockville?
Yes: plant out Apr 30 for a summer crop, and set out a second round of transplants by Jun 22 for a fall crop.
Nearby and related
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