Tomatoes: Vernalization

Richmond Hill, GA(Zone 8b)

Hi Carolyn and thank you for all your great posts here. :)

I have a question about tomatoes that I hope you can help me with. It's something that I've never really seen addressed on any gardening site. I'm sure this topic would apply to heirloom tomatoes and that's the vast majority of the tomatoes I'm growing this year. Could you explain vernalization as it applies to the tomato and exactly why it is necessary to induce fruit production? Thank you!


Bakersfield, CA

Some rambling comments on tomato vernalization. My habit to harden off tomato plants is to expose them to a few nights of cool air (45 to 50)F. as they are growing as transplants before they are big enough to take to the garden. I included below some more slightly out of context details that I though would enlighten the readership.

Temperature, like light, can affect plant growth both quantitatively and qualitatively. Many plants require exposure to a particular temperature before some physiological or developmental response can occur. Such temperature requirements can be important in limiting the geographic range of crop species. Tomatoes, for example, require a exposure to a minimum night temperature of approximately 15-20 oC (do the conversion to Fahrenheit yourself) in order to set fruit. This explains why tomato production is usually very poor in the tropical lowlands where night temperatures remain above this optimum.

Start seeds indoors 5 to 6 weeks before the last frost date. Do not wait too long to set the plants out; in order to set fruit, tomatoes need a period of vernalization with temperatures around the 40's. Taken loosely from Park's Seed Whopper tomato packet.

Plants grow better in alternating day and night temperatures than in a constant temperature environment. This is fairly true for tomatoes but this is not a true vernalization definition.

Vernalization. The act or process of causing a plant to blossom early by subjecting it to low temperatures.

What is the name given the scarring of tomato fruit which sometimes results from exposure to cold temperature? I know the answer, do you? This illustrates the danger of too much "vernalization" during flowering.

Certain tomato species require a vernalized period of cold temperatures of seed treatment, but unless you are growing the entire tomato collection from the Rick Tomato Center, chill out.

Tom of Bakersfield

Salem, NY(Zone 4b)


I'm sorry I wasn't able to get to the question you posed to me before now. I've been terribly busy and haven't been posting the past couple of days, as you can see from unanswered questions here in this forum that have been directed to me.

And I still don't have my tomato seeds planted. LOL

Vernalization means an exposure to certain lower temps which accelerate or promote development of flower buds which, when the plants are then grown at normal warm temps, may lead to increased earlier fruit production.

Depending on the specific plant variety, either seeds, or sprouted seeds, or plants at a certain stage, are exposed to lower temps for a certain length of time.

The word "vernum" means spring and the word vernalization was first used with repsect to the cold treatment of winter cereal sprouted seed which would then flower when plantd in the Spring. Spring sown cereal types don't need a cold treatment.

Vernalization is considered to be most important for those folks producing tomato seed on a commercial basis. In our temperate climates in most of the US such cold treatment is really not necessary. How many folks do you know of who cold treat tomato seedlings for a brief time at 50-55 degrees, which is the most commonly used temp? Very few home hobbyists do that although almost everyone knows that growing tomato seedlings at a reduced temp leads to a stronger, stockier plant. My commercial friend Charlie has special tomato greenhouses where he keeps the temps low during seedling growth. But I assure you Charlie is not knowingly vernalizing his maters. LOL If I told him that he wouldn't stop laughing. LOL And he laughs enough at my heirloom tomatoes for me to even think of talking to him about vernalization. LOL

Cold treatment with regard to tomatoes usually means to subject the seedlings to a temp of 50 to 55 degrees after the cotyledons appear and before the first set of true leaves appear, then bring the temps back up to normal. This induces flower buds which, when the plants are put outside, lead to earlier flowering with more flower clusters. If the outside temps are warm, all is well. Exposure to cold temps at the time of flowering and fruit set leads to, as I think most of you know, a condition called catfacing. Catfacing is also enhancd by high N levels and any disturbance to blossoms during pollination. There's some great pictures of catfacing in my book and Lord knows, everywhere on the web. LOL

Park Seed Co made a real boo boo at their webpage in referring to vernalization temps of about 40 re that new hybrid they are touting. That's too low and most folks reading that blurb don't have the faintest idea of what vernalization really is and it wasn't discussed.

Let me give you a reference to an excellent paper written about tomatoes and vernalization if you're really interested. I say that, because for home growers who have not done it in our temperate US climes, I can't see the sense in doing it. And how many folks have conditions where they can watch their various varieties develop, many at different rates, and be sure each variey is put at 50-55 degrees only for the period between cotyledon and first leaf time? LOL

Here's the URL:

Thats the superb website of Keith Mueller who got his MS degree with Dr. Randy Gardner at NC State. Dr. Gardner is a well known hybridizer and the developer of the Mountain series of hybrids. His own personl interest is in developing Early Blight (Alternaria solani) tolerant varieties but so far, as he says himself, he han't been very successful. He's released two such varieties but as he told me, it's of importance only to commercial growers where they may have to spray only every 8 days as opposed to every 5 days.

Any way, Keith didn't want to go to work for any major tomato company because of life style choices and moved back to the KC area several years ago. Last I knew he was working for a nursery and I really should write to him to catch up with his activities.

You can believe what you read at his site, which is really terrific. When you click in, go to seed starting and tip #1 where he's reproduced an excellent article on tomato vernalization.

Hope the above answers the question you posed.


Richmond Hill, GA(Zone 8b)

Thank you Carolyn and Tom! I first read about vernalization at the Park Seed site and I didn't know what in the heck they were talking about and tried to look it up. I couldn't really find the reason for vernalization and so I thought I'd ask you. Besides, I love to learn new things about my favorite...the tomato. :) These are the tomatoes I'm growing this year. As you can see, some are heirlooms and some are not. One thing's for sure! Lord willing, I'll have my craving for vine ripened tomatoes satisfied! LOL

1) Alicante
2) Amish Paste
3) Arkansas Traveler
4) Better Boy
5) Big Beef
6) Big Boy
7) Pink Brandywine
8) Burbank Red Slicing
9) Celebrity
10) Cherokee Purple
11) Creole
12) Georgia Streak
13) German Johnson
14) Hawaiian Pineapple
15) Hillbilly
16) Homestead
17) Isis Candy
18) Juliet
19) Mortgage Lifter
20) Mr. Stripey
21) Omar's Lebanese
22) Park's Whopper
23) Pineapple
24) Purple Brandy
25) Red Pear
26) Riesentraube
27) Roma
28) Rutgers
29) Santa
30) Sioux
31) Striped Cavern
32) Stupice
33) Sungold
34) Tigerella
35) Tommy Toe
36) Yellow Pear
37) Yellow Stuffer
38) Zapotec Pink Ribbed

Richmond Hill, GA(Zone 8b)

Oops! I forgot to thank you, Carolyn, for that great link to Keith Mueller's site. I popped over there for just a few minutes but I'm going back to read everything. It looks fabulous!


Salem, NY(Zone 4b)


You're well on your way to a serious tomato affliction. Anything I can do to aid and abet it I'll do. LOL

Just a few comments on your list.

Purple Brandy is a creation of Joe Bratka not a family heirloom. It's a cross between Marizol Purple and Pink Brandy. When he first sent it to me I named it Marizol Bratka so folks wouldn't think it was some kind of Brandy find, but both names are used and confusion abounds.

I knew Joe before he found out that making heirlooms was easier than finding new family heirlooms. LOL When he started creating them it caused a lot of confusion, and still does, with some folks trying to distinguish between the family heirlooms, like Eva Purple Ball, Marizol Gold, Zogola, and many others I got from Joe years ago, and his newer creations such as Isis Candy, Snowwhite, etc. And his father created the series of Box Car Willie, Great Divide, Lady Luck, Red Barn, Mule Team, Pasture, etc,none of which are family heirlooms despite the creative ad copy I see in many catalogs. I was as honest as could be when I entered those varieties at SSE, in terms of origin, and they've taken on a life of their own, much to my dismay.

He's still passing off some of his varieties as family heirlooms and one person in particular is entering them at SSE. But they aren't heirlooms at all. I know Joe has no living relatives back in Germany and his latest "family heirlooms" are from his "reltives" in Germany. Nope. But then he is an exceedingly creative gentleman, in many ways. LOL

Also, you list both Tigerella and Mr. Stripey. Tigerella was hybridized and selected for at the Glasshouse Research works in England and it and Tangella and Craigella came out of the same cross. Tigerella was called Mr. Stripey and to me and others still is the one and only Mr Stripey.

Enter WH who gave seeds of an ordinary large bicolor to a[person who grows heirloom tomato seeds commercially. it was named, unfortunately, Mr Stripey, because neither of these guys, although heavily involved with heirlooms,from a business standpoint, knew/know much about heirlooms. LOL

So now we have this bicolor large Mr. Stripey all over the place becasue it was promoted so heavily on the list of varieties sent out by this commercial place.

IMHO, and the opinion of many, Mr. Stripey is at the bottom of the list of good gold/red bicolors. But see how it does for you under your conditions this summer and then please report back.

Good looking list. I assume you have lots of room or the lawn and drivway are the next to go. LOL


Benton, KY(Zone 7a)

Thanks Terri for posing this question. It's been something that I've been curious about also. I knew about vernalization as a term,but needed it explained in depth by someone who understood the process.

Thanks Tom and Carolyn.

My list this season goes like this
and a local heirloom we call Uncle Mark Bagby's
This tomato was brought to the US by the great uncle of a friend of mine in 1919 (according to family lore)He immigrated from Germany and this potato leafed,large ,round,meaty pink supposedly came with him.It is grown all around west KY and has adapted well to our conditions.The tomato has a solid meat center and the few seeds are around the outside edges.It ripens late in the season(august) and I'm curious if it may be known by another name...hint ..hint

Again thanks for the link and the info on vernalization.The information is very helpful.

Salem, NY(Zone 4b)


Terri, I hope I remember to call you Terri in the future and not Pete. LOL But that blue name just sticks out there like a sore thumb.

Melody, it's about Uncle Mark. If I plant 50 large pink PL varieties in a row and you put a shotgun to my head, I still couldn't ID them by sight except for Gogosha, which is a light candy pink in color. Now as to taste, I could ID Sudduth Pink Brandy and that's about it. I've probably grown several hundred large pink PL varieties and they just aren't that different one from another. Oh, there are some that have a better plant habit, some that have less concentric cracking, some that usually are less prone to catfacing, etc., but as a group, give me the name on the seed pack and I feel more confident.

So Uncle Mark may also be Aunt Ginny or Sister Fidelma or Brother Amos, or whatever. And names do get changed.

Of the maybe 4,000 varieties listed in SSE I'd be willing to bet that no more than maybe 2500 to 3000 are unique.

It's a real problem and the only way it will ever get solved is to do DNA restriction mapping. LOL And you tell me who is going to foot the bill for that. No one, that's who.

So in my experience the large pink PL varieties have some of the best tastes around but it's almost impossible to ID them by sight or by taste.

Carolyn, who really is marching right into the other room and getting out that Jiffy mix and trying to find the seeds and planting them. Maybe.

Richmond, KY(Zone 6b)

>.....getting out that Jiffy mix.....<

Hmmmmm. Carolyn, if you don't stop procratinating I'm gonna just have to get out the whip. ;>)

Seriously, how far behind are you? Been 30 years since I lived in that neck of the woods, and have no recollection about when you would actually plant. Sometime in June, isn't it?

How many varieties are you planting this year?

Looking at those other lists, I'm beginning to feel like a slacker. I've only got 13 varieties going this year---six of which are stuffers, because I've got a project going on them.

Stuffers are: Schimmeig's Striped Hollow, Yellow Stuffer, Striped Cavern, Coursen Roy's, Brown Derby Mix, and Zapotec Pink.

Other than those, it's: German Pink, DePinto, Djena Lee, Black Krim, Old Flame, Grandma Brown's, and Tatyana's Azerbaijon. This gives me a cross section of types and colors, which is what I strive for each year. What I have is a beefsteak, a pase, a yellow, black, bi-color, and cherry. And an unknown.

The Tatyana's was collected in Azerbaijon, strictly as seed (the woman who got them never saw the actual tomatoes)and we're not sure what it will produce. The one time it was grown out was in a bad tomato year. Then it produced small to medium fruit, with a watery red or reddish orange color. Those of us growing it are kind of anxious to see what it does.

This message was edited Thursday, Apr 19th 8:42 AM

Richmond Hill, GA(Zone 8b)

Thanks Carolyn. :) I've grown some kind of Mr. Stripey before and I liked it. My DH did especially and that's the main reason I'm growing it this year. I have to say that it's not the perfect tomato in taste, for me anyway, but it was quite good. It was about as large as beefsteak, kind of orange in color with very vague shades of red scattered on the skin. The stripes were not very pronounced. The tomato was quite sweet tasting. The picture of Tigerella looks nothing like the Mr. Stripey that I grew. I'm looking forward to comparing the taste between the two tomatoes. I fear that Brandywine will not produce well for me here because of my hot, humid weather but I just had to try it. Next year I'll probably try another one of the Brandywines...Red Brandywine or OTV Brandywine maybe?

Mansfield, MO(Zone 6b)

Have you tried The Yellow Brandywine,
It yields 2 times the fruit and has a better flavor for us here in the Ozarks in Missouri....


Salem, NY(Zone 4b)


What you grew was the large bicolor Mr. Stripey which I described above. Tigerella, the original MR. Stripey is a l large cherry type with distinct gold jagged stripes. The two are completely different and no comparison is really possible.

As an alternative to Pink Brandy Jere has suggested Yellow Brandy.

I know that Red Brandywine and OTV Brandywine do quite well in your area; both of these are quite separate form Pink Brandy and you'll get none of the Pink Brandy unique taste. Same comment for the Yellow. And you might, as Jere suggested, try the Yellow Brandy. I'd get the Platfoot strain of Yellow Brandy for I find it to be very much better than the regular strain. It was sent to me by Gary Platfoot of Ohio, where Yellow Brandy was first found, and seeds are available from TGS.

Jere, did you see my post to you in the SSE thread? LOL


Richmond Hill, GA(Zone 8b)

Thanks Carolyn and Jere. I'll definitely give Yellow Brandywine a try next year.:)

Richmond Hill, GA(Zone 8b)

Carolyn, you've referred to PL varieties several times and I was wondering what that stands for? Does it stand for Pink Lycopersicon? Thanks! (sorry to be such an abbreviation dope. LOL)


This message was edited Friday, Apr 20th 11:04 AM

Salem, NY(Zone 4b)


I'm sorry.

PL is shorthand for potato leaved.


Richmond Hill, GA(Zone 8b)

Thank you, Carolyn! Now why didn't I think of that? LOL Did you get all of your seeds planted? :)


Humansville, MO(Zone 6a)

i was glad to see jere say that the brandywine otv did well in this area and will try the yellow next year i have 21 different types of tomato plants and the brandy wine are the best looking of all had 41 come up and i think all but two can be planted this was the best that anytype did

Salem, NY(Zone 4b)

Dave, that was me, Carolyn, who talked about OTV and REd Brandies, not Jere. LOL

Terri, yup, got all the seed plantd and delivered to Charlie's germination greenhouse and will report back here on varities and faves when I get the chance, which isn't now. LOL


Richmond Hill, GA(Zone 8b)

You know, if I get just _one_ tomato out of my Pink Brandywine plants, it will be worth it. I just have to taste that tomato for myself to see what all the fuss is about. Hasn't it been voted the best tasting tomato ever or something like that?


Salem, NY(Zone 4b)

No Terri, it hasn't been voted THE best tasting tomato ever. LOL

Taste testings are totally dependent on the varieties being tasted at one time in one place. And that makes such results variable and unable to be compared for the competition varies from tasting to tasting. LOL

Nevertheless Pink Brandy has a deserved reputation, IMHO, especially that Sudduth strain.

One of the reasons Pink Brandy is so well know is becasue it has been so accessible, It was amongst the first of the herilooms made available to the public thru Gleckler's in Metamora, Ohio, thus it's had a lot of exposure there and also thru SSE.

There are other varieties which are almost as good, according to lots of folks.

pretty pleae don't ask.LOL I've already listed some fomy faves. LOL

But THE best tasting tomato. Nope, not by a long shot. A great one? yes maa'am. LOL Remember p;lease, that taste perception varies with the individual.


Richmond Hill, GA(Zone 8b)

That's so very true, Carolyn. :)


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