Diamond Bar, California planting calendar and frost dates
Diamond Bar is in USDA hardiness zone 10a. The last spring frost typically comes around January 8 and the first fall frost around December 28, giving about 354 frost-free days a year.
- Hardiness zone
- Zone 10a
- Typical last frost
- January 8
- Typical first frost
- December 28
- Frost-free season
- 354 days
Frost dates in Diamond Bar
Last spring frost
- December 14Risky: frost later than this in 9 years out of 10
- January 8Typical: a later frost in half of years
- February 18Safe: a later frost only 1 year in 10
First fall frost
- December 5Risky: frost earlier than this 1 year in 10
- December 28Typical: an earlier frost in half of years
- New yearLate: in about 1 year in 10, the first frost waits until after December 31
The growing season between the typical last and first frosts is about 354 days. Frost here means a low of 32°F at the weather station.
NOAA U.S. Climate Normals 1991-2020 for Pomona/Fairplex, 2 miles NNW of the city center and 150 feet higher. Low-lying and rural spots often frost later in spring and earlier in fall than airports and city centers. Diamond Bar shares this station with Pomona, so the two cities have the same frost dates and planting calendar.
What to plant each month in Diamond Bar
January
Start indoors: basil, eggplants, peppers, tomatoes
Plant or sow outdoors: asparagus, avocados, beets, carrots, cauliflower, chives, cilantro, dahlias, dill, figs, garden mums, ginger, gladioli, grapes, green onions, lavenders, leeks, lettuce, lilies, marigolds, mints, nasturtiums, oregano, parsley, peppers, petunias, ranunculus, rosemary, roses, sage, snapdragons, spinach, sunflowers, sweet corn, swiss chard, thyme
Plant for fall: crocuses, garlic, hyacinths, ornamental alliums, tulips
February
Start indoors: basil, cantaloupes, celery, cucumbers, pumpkins, tomatoes, watermelons, winter squash, zucchini
Plant or sow outdoors: avocados, garden mums, green onions, st. augustinegrass
March
Start indoors: cosmos, cucumbers, okra, pumpkins, winter squash, zucchini
Plant or sow outdoors: basil, cantaloupes, cucumbers, eggplants, green beans, peppers, pumpkins, st. augustinegrass, tomatoes, watermelons, winter squash, zucchini
April
Plant or sow outdoors: cantaloupes, cucumbers, eggplants, green beans, peppers, pumpkins, tomatoes, watermelons, winter squash, zucchini
May
Start indoors: zinnias
Plant or sow outdoors: bermudagrass, celery, centipedegrass, cosmos, okra, peanuts, sweet potatoes, zoysiagrass
June
Plant or sow outdoors: bermudagrass, centipedegrass, zinnias, zoysiagrass
September
Start indoors: onions
Plant for fall: brussels sprouts, collard greens, cucumbers, lettuce, peppers, potatoes, sweet corn, swiss chard, tomatoes
October
Start indoors: broccoli, cabbages, cauliflower, collard greens, kale, leeks, onions, oregano, parsley, petunias, ranunculus, rosemary, snapdragons
Plant for fall: bearded irises, beets, broccoli, cabbages, carrots, cauliflower, collard greens, cucumbers, daylilies, green beans, kale, lettuce, peas, peppers, radishes, snapdragons, spinach, sweet corn, swiss chard, turnips, zucchini
November
Start indoors: black-eyed susans, broccoli, cabbages, cauliflower, chives, cilantro, collard greens, ginger, kale, leeks, lettuce, marigolds, nasturtiums, oregano, parsley, petunias, ranunculus, rosemary, sage, snapdragons, spinach, swiss chard
Plant or sow outdoors: asparagus, black-eyed susans, blueberries, garlic, grapes, grass seed, green onions, hollyhocks, kentucky bluegrass, onions, peas, poppies, raspberries, rhubarb, strawberries, sweet peas, tall fescue, turnips, wildflowers
Plant for fall: azaleas, bearded irises, beets, broccoli, cabbages, cauliflower, clematis, coneflowers, crocuses, daffodils, daylilies, grass seed, hostas, hyacinths, hydrangeas, kale, kentucky bluegrass, lettuce, lilies, ornamental alliums, peonies, perennial ryegrass, radishes, roses, saffron, snapdragons, spinach, tall fescue, tulips, turnips
December
Start indoors: cilantro, marigolds, nasturtiums, ranunculus, spinach, swiss chard
Plant or sow outdoors: asparagus, beets, black-eyed susans, blackberries, blueberries, broccoli, cabbages, carrots, cauliflower, chives, cilantro, collard greens, dahlias, dill, figs, garlic, gladioli, grapes, grass seed, green onions, hollyhocks, kale, kentucky bluegrass, leeks, lettuce, onions, parsley, peas, peppers, poppies, potatoes, radishes, ranunculus, raspberries, rhubarb, roses, snapdragons, spinach, strawberries, sweet peas, swiss chard, tall fescue, turnips, wildflowers
Plant for fall: crocuses, daffodils, daylilies, garlic, hyacinths, lilies, ornamental alliums, peonies, tulips
Frost dates and zones by ZIP code in Diamond Bar
All 2 of Diamond Bar's main ZIP codes take their frost dates from Pomona/Fairplex, so the dates on this page apply across the city. Every one of them is in zone 10a.
| ZIP code | Zone | Weather station | Typical last frost | Typical first frost |
|---|---|---|---|---|
| 91765 | 10a | Pomona/Fairplex, 2 mi NNW | Jan 8 | Dec 28 |
| 91789 | 10a | Pomona/Fairplex, 2 mi NNW | Jan 8 | Dec 28 |
Pomona/Fairplex also supplies the frost dates for Pomona and Chino Hills, so their planting calendars match Diamond Bar's.
Planting dates for popular crops in Diamond Bar
| Plant | Start indoors | Plant or sow outdoors | Fall planting |
|---|---|---|---|
| Tomatoes | Jan 22 to Feb 5 | Mar 19 to Apr 2 | Sep 14 to 21 |
| Strawberries | — | Nov 27 to Dec 11 | — |
| Lettuce | Nov 13 to 27 | Jan 1 to 15 | Sep 28 to Nov 2 |
| Cilantro | Nov 27 to Dec 11 | Jan 8 to 15 | — |
| Basil | Jan 29 to Feb 12 | Mar 19 to 26 | — |
| Potatoes | — | Dec 18 to 25 | Sep 7 to 14 |
| Garlic | — | Nov 27 to Dec 11 | Dec 28 to Jan 11 |
| Onions | Sep 18 to Oct 30 | Dec 11 to 25 | — |
| Cucumbers | Feb 19 to Mar 5 | Mar 19 to Apr 2 | Sep 28 to Oct 12 |
| Pumpkins | Feb 19 to Mar 5 | Mar 19 to Apr 2 | — |
| Peppers | Jan 1 to 29 | Mar 19 to Apr 2 | Sep 7 to Oct 5 |
| Carrots | — | Dec 18 to Jan 8 | Oct 5 to 26 |
| Sweet Potatoes | — | May 6 to 13 | — |
| Watermelons | Feb 12 to 26 | Mar 19 to Apr 2 | — |
| Sweet Corn | — | Jan 8 to 22 | Sep 21 to Oct 5 |
| Green Beans | — | Mar 19 to Apr 2 | Oct 5 to 12 |
| Zucchini | Feb 19 to Mar 5 | Mar 19 to Apr 2 | Oct 5 to 19 |
| Broccoli | Oct 23 to Nov 13 | Dec 11 to 25 | Oct 12 to Nov 9 |
| Peas | — | Nov 27 to Dec 11 | Oct 5 to 19 |
| Spinach | Nov 27 to Dec 4 | Jan 1 to 15 | Oct 19 to Nov 23 |
| Sunflowers | — | Jan 8 to 29 | — |
| Zinnias | May 16 to 23 | Jun 13 to 27 | — |
| Tulips | — | — | Nov 16 to Jan 11 |
| Daffodils | — | — | Nov 16 to Dec 28 |
| Grass Seed | — | Nov 27 to Dec 11 | Nov 16 to 30 |
Nearby cities
- Pomona, CA zone 10a, last frost Jan 8
- West Covina, CA zone 10a
- Chino Hills, CA zone 10a, last frost Jan 8
- Yorba Linda, CA zone 10a
- Placentia, CA zone 10b
- Chino, CA zone 10a
Planting in CaliforniaAbout zone 10aPrintable calendar for Diamond Bar
Questions
When is the last frost in Diamond Bar?
Around January 8 in a typical year, based on NOAA's 1991-2020 records for Pomona/Fairplex. There is still a 1 in 10 chance of frost after February 18.
What planting zone is Diamond Bar in?
USDA hardiness zone 10a (2023 map). The zone tells you which perennials survive the winter; planting dates depend on frost dates instead.
When should I plant tomatoes in Diamond Bar?
Start seeds indoors January 22 to February 5 and set plants out March 19 to April 2.
When is the first frost in Diamond Bar?
Around December 28 in a typical year, and before December 5 about 1 year in 10.