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California Gardening

What are your last frost dates?

15 years ago

I am in the Santa Cruz area and they list us nationally as the end of Feb. for our last frost dates. I know we have had frost overnight as late as April. In the 22 years I have been living here I have delayed planting my tender plants from March 1st to May 1st.

Does anyone know where you can find accurate information about frost dates? I find Sunset's zones not the most accurate because of all the micro climates here.

Thanks.

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Comments (8)

slo_garden
15 years ago
I'm in San Luis Obispo and our last frost date is March 15th. My mom is in Santa Cruz and she said its about the same there. I think there are always those freak, outside chances that you could get frost after that, but it is highly unlikely.
Babka NorCal 9b
15 years ago
Micro climates change everything. I'm in the Santa Clara Valley (Sunnyvale) and I go to Weather Bug and can see the difference in temps recorded from 2 miles in one direction to 2 miles in the opposite direction. I suggest you get a thermometer and record the nighttime lows in the spot where you plan to plant...but then that will also be only a yearly average. We get a killing freeze about every 9 or 10 years, and the rest of the time things are okay. Sunset paints with a broad brush, but they are much more detailed than most other maps.

I recently went looking for the chill hours for Santa Clara county, and NONE are recorded. I e-mailed the fruits and nuts at davis edu, and they don't have the info either.

I can plant tomatoes here on the south side of my house against the white stucco on April 1st. Elsewhere in my yard they won't get enough heat that early, so there are even micro climates on my little chunk of real estate.

Good Luck!

-Babka
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Conditions now have nothing to do with last frost date. LFD is calculated to give a typical idea, thus giving us gardeners the ability to estimate based on historical data for a particular area. Using conditions in January will not give you a viable reference point for the possibility of ambient temperatures dropping below the freezing point two months from now. It is not uncommon in some areas to see a frost even after spring days in the seventies, and possible almost anywhere. Your best bet is to stick with the closest available data to your exact location, adjust for microclimate if need be, and hope you don't get an unexpected cold snap. Why risk poor growth or loosing an early planting to gambling on a few extra days' head start? There are plenty of crops that can be safely planted outdoors before LFD, so you can satisfy your urge to garden without putting more tender crops at risk. If the timing is critical for some reason, you would be better served by employing some common season-extension techniques, such as heat absorbing mulches and row-covers to retain heat gained during the day. In my 20+ years of gardening, planning to beat LFD is an optimistic and more often than not failed pipe-dream.
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Hate to break this to you, Kawaiineko gardener, while there is a technical last and first frost date for Boyne City and the rest of northern Michigan, these are just averages, and ... well, as we all know, there are always outliers. Frost can and does happen every month in your part of Michigan. My uncle lives about an hour south of you near Cadillac, in a place called Tustin, and my sister lives just outside of Manistee. Both of them have had hard freezes in mid to late June and again in early September, and both have reported frost even in July and August, albeit light ones that didn't really hurt anything. It happens. Last year was especially challenging up there, with late, hard freezes in May and hard frosts in June. My uncle lost his garden twice to frosts, first around Memorial Day, and then again about 3 weeks later after he had replanted. Both of them said it was really hard to find transplants at the local greenhouses because everyone got wiped out and had to do it all over again at least one time, some people twice. The year that my sister moved up there for good, 1993, they also had 4 inches of snow on August 28th, although it melted away by 10:00 the next morning. We had it really cold, wet, and windy the same day, with a high around 48 and a low around 42, but no snowflakes, thank goodness. And, it turned around and got up to like 93 the next week. Michigan weather is just plain WIERD. I hope this year will be better. Even down here near Detroit it was COLD, COLD, COLD all summer. July had several nights where the thermometer in my backyard hovered around 38 degrees, just above the point frost could begin to form.
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I am confused by the "last frost" date. Frost occurs when temperatures are 39F or below and the night sky is clear. A frost hardly implies damage to any fruit blossoms, let alone even tropical things like bananas. You need air temperatures below 32F for blossom damage. In fact, you need 28F for apples, 30F for stone fruits. I think the last frost date in Calif. is a joke, the Central Valley around Modesto has seen plenty of blossom damaging freezes well into the March/early April time frame. Besides, in California, there is so much variation in the degree of cold, it can literally vary heavily within even a quarter mile based on terrain and distance from the ocean. The Santa Cruz mountain foothills don't usually see any hard frost after Feb. 21, but in the mountain valleys, a hard frost can occur as late as May. Speaking of light frosts, the colder canyon/valley locations around the Santa Cruz mountains get Summer light frosts. There have even been reports of windshield frost mid Summer in the colder valleys - yes, this is California. For example, the low was 39F in Santa Cruz on June 25, 1975. How about a low of 40F on July 24, 1973 or Aug 5, 1950. How about 38F an Aug 11, 1981, and another 39F reading that same year on the 24th of August. I hope you see now why we can grow such incredible Summer apples. My Gravensteins store until January thanks to the cold Summer nights. Of course, in the Central Valley, just 50 miles straight due East you would never dream of seeing anything below 50F in the Summer, the coldest records are around 48F. However, lows 32F and below occur all the way until April 1. See http://www.wrcc.dri.edu/summary/Climsmnca.html. The trick for Apricots is to keep them dormant as long as possible. I have a row of Apricots growing on a north slope, and they are just now starting to push buds. Bloom should be in full swing by the end of March. Then there is frost floating row cover - good enough to keep Spring frosts off a blooming backyard apricot tree.
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Cheyboygan's frost dates are 5-30 (last) and 9-25 (first). Traverse City's dates are 6-9 and 9-17. You are between them. Of the two, Traverse City's is the shortest season, so unless you have something that makes your area colder than that, those dates should be relatively safe for you. Just keep in mind that the frost dates listed for ANYWHERE are just averages, they aren't engraved in stone. Keep an eye on the weather report, and if a frost is expected, run out and cover your seedlings (except for cole crops, which should be okay). Or, contact your most-local Cooperative Extension Service and ask: Phone: 517-355-2308 Toll Free:1-888-MSUE-4MI (1-888-678-3464) Fax: 517-355-6473 (their email address info was having problems) Sue
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kristincarol
15 years ago
As unbelievable as it may seem, last frost dates here in Humboldt County are 5/15, although there is plenty that can be put in before that which will survive light frosts such as we get in later Spring.

Can't grow tomatoes or other hot weather veggies here AT ALL because of the proximity of the ocean and also the foggy summers (I tried beans, eggplant, corn and tomatoes early on in my time here and it was very, very sad.) Have had some luck with those crops a 1/4 mile more inland and with some altitude thrown in so, yes, micro-climates make all the difference.
calistoga_al ca 15 usda 9
15 years ago
When considering last frost dates keep in mind those are an AVERAGE last frost date. Gardeners are always taking a risk that a late frost may occur well beyond the average date. As for chilling hours, those are hours below 45 degrees and the Santa Clara valley before it was paved has a long history as a fruit growing area. You county UCCE extension can give you the average as well as the year to date of chilling hours. Al
Babka NorCal 9b
15 years ago
Al- I went there and here's what I got...no info posted since last Oct. The same outpost does the chill hours for the Pomology report. Someone must've removed their funding.

-Babka

Here is a link that might be useful: No numbers since last Oct.
Babka NorCal 9b
15 years ago
Correction: Actually there is no info since April of 2008. Someone was at least posting the "zeros"for a while. I'm just a home gardener. Where do the orchard growers (there are a few left in the Santa Clara valley, I think) go to get this info. I can get local highs and lows, but not chill hours.

-Babka
calistoga_al ca 15 usda 9
15 years ago
babka they may not be posting on a website but I think they have them at the local Santa Clara office. Have you telephoned them? Al
Babka NorCal 9b
15 years ago
Al-

Thanks. I didn't even think about calling locally as I just figured this info would be available on-line. I e-mailed the folks at the California Pomology website, and the pomology person at UC Davis responded by copying me on an e-mail to the Monterey fellow, asking why nothing is posted. I'll take your advice and do it the old fashioned way and pick up a phone and see what I can find out that way.

I don't have fruit trees, but rather a collection of hostas that need those chill hours. I thought it would be interesting to have the chill hours to compare over the years with regard to how the hostas thrive or dwindle.

Thanks,

-Babka

Here is a link that might be useful: Pomology Weather

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