how much heat is enough for star ruby?

[adriano2]

How much heat does it need for star ruby to get red and sweet? I know it gets red in Florida and Texas. Can it get red and sweat in California or in Mediterranean? Does it have anything to do with rootstock?

[Millet]

Grapefruit achieves its best quality under conditions of hot days and warm to hot nights, which results in higher sugars and lower acids than grapefruit produced in the cooler night temperatures common in Arizona and California. Therefore, California grapefruit production is regulated to the interior areas of the state such as Riverside where heat unites in the areas of 3200 to 3500 heat unit degrees. - Millet

[brian]

i remember looking up something similar, you can find "degree day" charts for the entire US.  I was wondering the same thing and it looks like we get enough heat in southeast PA for me to ripen these.

Check here and compare to heat requirements for the variety:  http://uspest.org/US/

[Millet]

Heat plays a role in determining the time of fruit maturity and the level of fruit quality.  The heat requirement is determined by the number of hours that the temperature is above 55-F from the time of bloom to maturity.  In general, grapefruit have the highest heat requirement, about 11,000 heat unites. In contrast Valencia oranges about 10,000 heat unites, and Washington navel about 8,000 heat unites.  Citrus varieties that have lower heat requirements mature earlier than do those with high heat requirements. Also, in general, varieties that mature early in the season require less time between bloom and fruit maturity than do varieties that mature later in the winter or spring. - Millet

[adriano2]

thanks guys. I ask because i planted one 2 years ago in my area which has typically med climate. The tree was raised on Sicily, but there is much more heat than here in my place. If nothing, it is going to be interesting experiment. Valencias and navels thrive well here on Dalmatian coast.  What is with moro and tarocco? They mature late in season. Do they also need a lot of heat? 

[adriano2]

Heat plays a role in determining the time of fruit maturity and the level of fruit quality.  The heat requirement is determined by the number of heat unites that the temperature is above 55-F from the time of bloom to maturity.  In general, grapefruit have the highest heat requirement, about 11,000 heat unites. In contrast Valencia oranges about 10,000 heat unites, and Washington navel about 8,000 heat unites.  Citrus varieties that have lower heat requirements mature earlier than do those with high heat requirements. Also, in general, varieties that mature early in the season require less time between bloom and fruit maturity than do varieties that mature later in the winter or spring. - Millet

i do not understand. what does 11000 hours mean in term of 1 year?  It is 458 days in case all days and nights are above 55 fahr. or 12,7 C? It seems to much.

[Millet]

adriano2, I see that my last post confused you. Sorry that I did not make it clear.  There is no one time span verses the amount of heat unites required to mature a grapefruit.  A grapefruit growing in Riverside California would take approximately 15 months to accumulate heat unites required to mature a grapefruit.  On the other hand, a grapefruit tree growing in the hot Imperial Valley desert of southern California could receive the required amount of heat unites to become mature in perhaps 8 months.  Further the Imperial Valley would produce a grapefruit of a much higher quality.  In your case wherever you wish to plant your grapefruit tree, you should first find out the available heat unites for your location.  Following is a good example.  Grapefruits in the Coachella and Imperial valleys of California commonly reach maturity from four to six months earlier than at Riverside just seventy miles west on the coastal side of the mountains.  Coachella Valley has approximately the same average heat unit index as Imperial Valley, namely  for the growing season +6078 degrees and for the dormant period +11 degrees, whereas the same comparative figures for Riverside California are +3209 degrees and -217 degrees - Millet

[adriano2]

Thanks. I understand now. Unfortunately i have already planted star ruby 2 years ago. At that time i did not think about these things, because all citrus sports have so far managed to grow and produce here at my place.

[Millet]

adrino2 I also grow Star Ruby grapefruit inside my greenhouse.  The greenhouse temperature during the spring and summer 84-F day and 60-F night.  Winter temperatures are 74-F day and  52-F night.  The fruit does color up well, but the quality is just fair +-. - Millet

[GregBradley]

I thought Star Ruby only did really well in extreme south Texas where it is really hot. I was told to plant Rio Red instead in my hot interior SoCal valley, almost as hot as Riverside 25 miles further inland.

[Millet]

Greg, that's correct.  That is why even in my greenhouse (84-F high) Star Ruby only produces a fair quality fruit.  I also have two Marsh white grapefruit.  They do great. - Millet

[adriano2]

adrino2 I also grow Star Ruby grapefruit inside my greenhouse.  The greenhouse temperature during the spring and summer 84-F day and 60-F night.  Winter temperatures are 74-F day and  52-F night.  The fruit does color up well, but the quality is just fair +-. - Millet

I have similar summer day temperatures 83 F. Night summer temperatures here are 70 F.  However my winter temperatures are 55 fahrenheit day and 45 night. This is average in time span 1960-1990. last decade was warmer, especially last 2 years which were extremely hot. Daily highs did not drop under 30 C whole july and august.

[GregBradley]

My climate is close to Riverside. Today's 84F High & 64F Low is very unusual for Summer. Normal June, July, August & September cooler days are 90F/65F and hotter days are 100F/72F. We generally get a week sometime when we see almost 110F each day. We usually see a few days above 110F but not every year.

My older unidentified GF produces fabulous grapefruit. Patty S identified it as a Pink Marsh or similar from the picture below shown with one of my Cocktail GF.

I have since readied a GF section for my grove with Oro Blanco, Melogold, Rio Red, another Cocktail

[Millet]

Greg, I have a interesting (or at least to me) question about the ripening time of your Oroblanco.  You wrote that Riverside, CA and your location have the same weather. I interested to know when  Oroblanco ripens in your location?  Oroblanco matures from early December to March in Riverside and from late November through February in the San Joaquin Valley. Thanks Millet

[adriano2]

http://www.homecitrusgrowers.co.uk/citrusplaces/valrahmeh.html

Star ruby in Menton in south of France. It looks good at first, but who knows what does it taste like.

[Mark in Texas]

Star Ruby and it's successor, Rio Red (and my fave) need heat, lots of it to really excel, and excel they can!   I grew "tons" of Rio Red on one tree in Corpus Christi, zone 9b.  It was usually at it's prime come Feb.-March after going thru the usual mild to moderate winter.

The heat is on there with night time lows @ 80F and day time highs of 95F, (26.5C/35C).  With such conditions the meat turns red, sugar is up, skin will have quite a bit of pink and red coloration and I know I'm going to get some heat for this but the citrus quality of south Texas fruit is far superior than any grown in other citrus growing states.  It has more juice, is richer with more flavor and better color which I attribute not only to the clime but the soil.

  Ahhhhhhh yes, Citrus Terroir!   

Good luck

[GregBradley]

Millet,

I'm sorry but I don't have your info as I bought my OroBlanco just over a year ago.

The ripening time you quoted make sense as California's central valley can really sizzle in the Summer, almost as hot as the Imperial Valley.

My favorite race track to run my track motorcycles is Buttonwillow, Northwest of Bakersfield. Its a good place to avoid in the peak of Summer as it hits 100F almost every day. No wonder there is so much cotton grown there.

[fruitmentor]

Hi Adriano,

Grapefruit are not very good in the Mediterranean climate here in northern California where I live. The scientists at UC Riverside have bred a number of pummelo hybrids that do better than grapefruit here. I actually like them much more than grapefruit.

I wrote an article about them and you can read it here:

http://www.fruitmentor.com/CaliforniaPummelos

I do not know if any of these hybrids are available in Europe, but I imagine that they would do well there. If they are not available, I do not believe there is anything that would stop them from going to Europe. The ones that were patented now have expired patents. The Valentine Pummelo hybrid was recently released as public domain. Of course they would have to go through a quarantine and clean up to go to Europe, so someone would have to pay for that.

I hope this helps.

Best regards,
Dan Willey

[Mark in Texas]

Hi Adriano,

Grapefruit are not very good in the Mediterranean climate here in northern California where I live. The scientists at UC Riverside have bred a number of pummelo hybrids that do better than grapefruit here. I actually like them much more than grapefruit.

I wrote an article about them and you can read it here:

http://www.fruitmentor.com/CaliforniaPummelos

I do not know if any of these hybrids are available in Europe, but I imagine that they would do well there. If they are not available, I do not believe there is anything that would stop them from going to Europe. The ones that were patented now have expired patents. The Valentine Pummelo hybrid was recently released as public domain. Of course they would have to go through a quarantine and clean up to go to Europe, so someone would have to pay for that.

I hope this helps.

Best regards,
Dan Willey

Taste tests sound much like the Rio Red grown in hot climates.  You don't have a lot of seeds to mess with either.

Great link and great info, thanks for sharing.  Ever tested the brix on those pummelos?  IMO, if a tasting/rating panel does not have a refractometer in its tool box, it's not a valid test, purely anecdotal.

Mark

[fruitmentor]

Hi Mark,

I wish that you could have joined one of the tastings and tasted those fruit for yourself. It is not like comparing grapefruit to each other. The flavors are so different that you do not need a refractometer to tell the difference. I like grapefruit and I have had some very good ones including fresh from the tree in Florida and California and store-bought ones from Texas. I prefer most of these pummelos and pummelo hybrids to grapefruit.

Most Americans only know about grapefruit and if any of these other fruit were to appear in a store, people would not buy them because they do not know about them. It is a shame. I believe that most of these that are grown in California are exported to Asia where people appreciate them and pay a premium for them.

Although some of these fruit are quite messy and I suppose inconvenient to eat, I still prefer them to grapefruit. Sometimes I find myself eating a Cocktail pummelo hybrid over the kitchen sink like a barbarian with the juice dripping everywhere. It is worth it for the taste.

I hope that you have the chance to try them. I also hope that I have a chance to try one of those perfectly-ripened Texas Rio Reds right off of the tree someday!

Best regards,
Dan

[Mark in Texas]

Dan, sounds like a treat.  We get pummelos in our local stores.  I'll make sure to give them a try.

Thanks!

[adriano2]

Hi Adriano,

Grapefruit are not very good in the Mediterranean climate here in northern California where I live. The scientists at UC Riverside have bred a number of pummelo hybrids that do better than grapefruit here. I actually like them much more than grapefruit.

I wrote an article about them and you can read it here:

http://www.fruitmentor.com/CaliforniaPummelos

I do not know if any of these hybrids are available in Europe, but I imagine that they would do well there. If they are not available, I do not believe there is anything that would stop them from going to Europe. The ones that were patented now have expired patents. The Valentine Pummelo hybrid was recently released as public domain. Of course they would have to go through a quarantine and clean up to go to Europe, so someone would have to pay for that.

I hope this helps.

Best regards,
Dan Willey

NIce article. You are true citrus expert. Unfortunately there are no pummelos trees to buy here. I bought one pummelo in supermarcet some time ago, it tasted sweeter than white grapefruit. The size of that pummelo was huge. I broke my citrus machine while making juice.

[adriano2]

this is star ruby i was talking about. It is going to be interesting to see development of those flowers and taste of the fruit.



upload photo

how do i print screen

[MangoFang]

Adriano - Star Ruby is the exact Grapefruit tree that I have here in the desert of Palm Springs
California, and Millet is quite right - they adore heat, heat and more heat. I've got about 70-80 fruit
on my 10 year old tree right now - should be ready by mid December.  And let me tell you my friend,
It is by FAR the best grapefruit I have ever eaten - like sunshine with a bit of attitude (the acid I suppose)

 

Gary

It's in a corner of the yard with lots of other plants around so hard to get a good full shot of it.  It's about 15 ft X 15 ft. Much of the fruit is hidden but here it is:

[adriano2]

your tree is very large, especially for star ruby, which is one of smaller grapefruit, at least i read that somewhere.

[Mark in Texas]

Adriano - Star Ruby is the exact Grapefruit tree that I have here in the desert of Palm Springs
California, and Millet is quite right - they adore heat, heat and more heat. I've got about 70-80 fruit
on my 10 year old tree right now - should be ready by mid December.  And let me tell you my friend,
It is by FAR the best grapefruit I have ever eaten - like sunshine with a bit of attitude (the acid I suppose)

 

Gary

It's in a corner of the yard with lots of other plants around so hard to get a good full shot of it.  It's about 15 ft X 15 ft. Much of the fruit is hidden but here it is:

If you like Star Ruby, you'll love the irridated sport from the Ruby even more - Rio Red.   Here's the history on it:
http://www.yaac.net/riored.html

Rio Red on sour orange rootstock grown in clay soil is really hard to beat regarding tree and fruit quality.

Mark

[MangoFang]

Yes, Mark in  Texas, I'd love to try Rio Red!  I've heard of them and think I've seen little 3 gallon
plants at Home Depot if I'm not mistaken.....but now I've got no room with that large tree I have....well, not just that one but also the 20+ mango trees I've got...

Gary

[Millet]

Most any citrus grown on Sour Orange root stock produces a great tasting fruit.  (Provided the tristeza virus is not in your area). - Millet

[Yorgos]

Millet, I am still confused about the heat hours.  Here in Houston, TX March thru November (assuming every hour is above 55, which is doubtful for some # of hours in March and November), you only have max 6,600 hours total (275 days x 24 hrs)!  An entire year only has 8,760 hours total (365 days x 24 hours)! So even in tropical climes it would take more than a year for grapefruit to ripen. That doesnt seem right. Can you 'splain it to me?

[Millet]

Yorgus, it is not the amount of heat hours, rather it is the amount of heat unites.  Going back I see that I mistakenly used the word hours in one of my posts instead of unites, I corrected that post. I apologize for my error.   As far as time from bloom to maturity, a grapefruit generally takes about 9 months, more or less depending on the trees location.- Millet

[adriano2]

my star ruby is now blooming. Is this unusual for grapefruit to bloom this late?

[Yorgos]

Thanks for the clarification Millet.  I went out and did some research and developed a spreadsheet. So, in Houston, Texas, if a grapefruit tree bloomed in mid-March a tree would have attained the magical 11,000 Units by early Sept. 
However, the fruit is still green in Sept and won't color up until December or so. Since flavor peaks in Feb. how does reaching the 11,000 DHU mark in September play into that?
 

[Millet]

A good number of people are not crazy about commercial grapefruit, mainly because they are pick early, at or near the 11,000 heat unit time period.  Of course commercial growers want to harvest as soon as possible for economic reasons. The 11,000 heat unites is assumed to be acceptable for harvest. This measure was set some times back.  In recent times many new varieties, especially reds, have come into existence. I am not sure what the heat unit number is for each individual cultivar. However, it is also known that the longer a grapefruit hangs on the tree, the the better the quality becomes.   Of all the people that I personally know, the one person with the highest level of intelligence on the science concerning the production of  citrus, Dr. Malcolm Manners PhD,  (Florida Southern University) once told me that grapefruit left hanging on the tree until March produces the most fantastic tasting grapefruit possible.  He further stated that of all the different grapefruit cultivars, the white fleshed Marsh grapefruit is the best of the best (at least in his estimation.) - Millet

[Mark in Texas]

Thanks for the clarification Millet.  I went out and did some research and developed a spreadsheet. So, in Houston, Texas, if a grapefruit tree bloomed in mid-March a tree would have attained the magical 11,000 Units by early Sept. 
However, the fruit is still green in Sept and won't color up until December or so. Since flavor peaks in Feb. how does reaching the 11,000 DHU mark in September play into that?
 

I wouldn't give it much thought, just do it.  I had excellent citrus while living in Corpus Christi which has the same clime as yours.  Citrus was on sour orange, same high pH "Victoria black clay" soil as yours.  My Rio Red was delicious, every year.  They do best with high summer heat and fairly cold winters, even standing cold into the low 20's with no damage.  Of course that Rio Red had a trunk girth of 10" too, and it was planted on the north side of the house.  After thought was that was a bad move....it loved it.

Temps held in the mid to upper 20's for a few days.  Fruit was fine.

Rio Red, Xmas 2004:



Orlando tangelo, same Xmas:

[Yorgos]

Not acummulating may heat units that day!  What fantastic pictures. Ive always run out and picked all my citrus before a hard freeze.  I guess I wont be doing that anymore. 
We rarely get snow here on the upper Guf coast but usually get a few days when the temps dip down to the mid-upper twenties every winter.

[Mark in Texas]

Yep, kissed oh so sweetly by some of that good ol southern snow.

ahhhhhhhhhhh........