Clementine x Thomasville 2024 in Greenville NC

[a_Vivaldi]

Last year I made a handful of hand pollinations of an unknown variety of clementine with Thomasville citrangequat pollen. The resulting fruits ripened in November and yielded a bit less than a hundred seed. Now that the seedlings have had time to differentiate in terms of form, vigor, and health, I've decided I might as well share the progress so far.


One of the fruits.


Seed from that fruit. Ordinarily clementines are seedless as they are self-incompatible, but when pollenated they can be fairly seedy.

[a_Vivaldi]

One of the community trays I germinated seeds in.


I immediately culled any seedlings with malformed roots and those that showed very poor vigor or chlorosis.

Once the seedlings sized up and demonstrated good vigor, I transplanted them into individual pots. This process occurred over a two month period since germination rates were not even and some seedlings were slow to get going but showed good vigor afterwards.

One of the seedlings that I transplanted had germinated on a buried piece of wood mulch and the root went right through a crack and came out the other side. I labeled this seedling as it wasn't clear if it would be harmed and I was curious to see how it performed.

[a_Vivaldi]

By February I had finished transferring the seedlings to individual pots and culling the worst performers. Some plants were starting to show differences in leaf form, but by and large it was too early to really confirm that the clementine I had used was a true clementine and zygotic.

[a_Vivaldi]

In May I began transferring the larger seedlings to new pots and moving them outdoors. At that time, one of them displayed exceptionally uniform whorls, which was amusing.






That plant has since lost its perfect form and mostly looks like any other unfortunately with new leaves at more or less random angles.

[a_Vivaldi]

By June the different forms were really beginning to show. Some of the more distinct ones being these:


Larger leaves that are fairly straight with a strong vein the in middle. Weak roots. almost thornless even as a seedling.


Wider leaves with a more blunt tip. Longer thorns, vigorous.


More wide, blunt leaves. Short thorns, vigorous. Leaves perfectly whorled at the time.


Long, narrow leaves, few thorns, decent vigor. This was the seedling that grew through a stick.


Similar to the previous but with shorter internodes.


Very upright leaves that are fairly elongated and pointed, long petioles


Deep venation and wrinkled leaves. Leaning for some reason.


Upright habit, almost no petiole, short thorns. Somewhat poor roots.


Very broad leaves with no points, thornless, and almost no internodes. Stunted growth, highly dwarfed. Almost culled.


Extremely stunted, very poor roots, weird, sickly little plant. The last of the plants not to get culled, though it was on the chopping block and was only saved because of the very dense growth habit it started showing.

At this point, I had culled the majority of seedlings, having about a third or a quarter of the initial batch left.

No plants showed trifoliate leaves, or bifoliate for that matter. The leaves have a wide range of flavors from mandarin-like to bitter to lemony.

[a_Vivaldi]

Through June and especially in July, the plants have started growing a lot and the most vigorous ones have begun differentiating themselves from the rest.

[a_Vivaldi]

At this point, I'm confident enough to go ahead and label them serially, I'll use CT4-1, CT4-2,... to keep the names short so that in later crosses I don't have to write out a paragraph for each one since stuff like (clementine x (citrus fortunela "Nagami" x (citrus trifoliata x citrus sinensis "Rusk) "Thomasville")) "ClemTom" x ((citrus trifoliata x citrus paradisii "Duncan") "Dunstan" x OP) "Dunson" is a bit much to write out on a label haha

I have zero expectations of hardiness from this cross. At best, mid-teens. However, I suspect I'll get something close to 50/50 plants with zygotic seed which will make backcrossing with trifoliate hybrids easier.

[a_Vivaldi]

Six so far appear to be completely thornless. Two or three others might be, but they're also just have very poor vigor and I've had a few that have developed thorns or gotten thornier during stronger growth.

I'm thinking these seedlings will finish their first year ranging from 6 inches up to perhaps 2 feet or more tall, which is a lot of variation. I wonder if I push them hard if I might be able to get one to hit a meter tall before winter dormancy sets in... I don't think I'll try that, though, since I need them to slow down by late summer so they'll harden off.

Honestly, for F1 hybrids I'm surprised at how different they all look with no plant exactly like another despite having two dozen of them. Thomasville's very heterozygous genetics probably are the main contributor there, though it might also help that clementine has a bit of orange in its background. One or two of the seedlings seem to have managed to combine the little bit of orange from clementine and the Ruby genes from Thomasville and ended up with more orange-like leaves. Internode length is another one that's all over the place with these, some of them showing longer internodes than either parent and several of them with some kind of dwarfing effect. I'm sure many of the culled seedlings were also dwarfs and perhaps might have been interesting from that standpoint but I've limited myself to growing out only a handful of defective, low-vigor seedlings. I did save the weirdest of the dwarfs anyhow.

[a_Vivaldi]

Despite the Ruby ancestry, none of the plants at any point have shown pigmentation in their new growth. I'll keep an eye on any growth that occurs in the fall or next spring to see if pigmentation develops.

[Skandiberg]

Good job, congrats! Those are nice plants. Thomasville can be an exciting breeding partner due to its complex genetics, as you also pointed out. You have a fair amount of variability among your seedlings. I would have expected some trifoliate ones from that cross.

[a_Vivaldi]

I would have expected some trifoliate ones from that cross.

I think it's far enough removed that the trait didn't get passed on. CL4s are only 1/8 trifoliate, even US-119, which is monofoliate, is 1/4 trifoliate.

Trifoliate leaves are definitely a multi-gene trait, since it doesn't follow Mendelian inheritance (often becoming a different trait with mixed mono and trifoliate and/or bifoliate leaves in the second generation). There's something about it that is a true dominant gene, since every F1 trifoliate hybrid has trifoliate leaves, but after the initial cross it stops behaving Mendelian.

[bussone]

Honestly, for F1 hybrids I'm surprised at how different they all look with no plant exactly like another despite having two dozen of them.

Not that surprising. Many of the famous citranges were just different seedlings from the same two parent trees.

[a_Vivaldi]

even US-119, which is monofoliate, is 1/4 trifoliate..

Clearly I don't even pay attention to the trees in my own yard... US-119 is a mixed leaf form variety.

[David Kipps]

Did the clementine parent you started with have thorns?  I've wondered just how the totally thornless is inherited.  I once planted the seeds from some store bought clementine fruit, and got two plants that have always been totally thornless from the start.  Also planted seeds from a store bought Meyer lemon fruit and got a totally thornless plant.

[a_Vivaldi]

The parent Clementine is thornless, even in vigorous new growth.

Thomasville isn't especially thorny so perhaps that helps as well? For the CT4 plants with thorns, they range in size from tiny to pretty significant but not crazy huge.

[Curiousgardener23]

This is a cool cross! Thank you for posting about it and I'm interested to hear how they turn out. The variability in the seedlings makes me think that the fruit from the seedlings will be really interesting to compare.

[BorisR]

a_Vivaldi, great results! Excellent growth rate! What are you using to fertilize them? And what will you call the same hybrids produced in 2034?))

[Ilya11]

I would have expected some trifoliate ones from that cross.

I think it's far enough removed that the trait didn't get passed on. CL4s are only 1/8 trifoliate, even US-119, which is monofoliate, is 1/4 trifoliate.

Trifoliate leaves are definitely a multi-gene trait, since it doesn't follow Mendelian inheritance (often becoming a different trait with mixed mono and trifoliate and/or bifoliate leaves in the second generation). There's something about it that is a true dominant gene, since every F1 trifoliate hybrid has trifoliate leaves, but after the initial cross it stops behaving Mendelian.

Still, the majority of my F3 exhibit at least occasional bi-tri foliate feature.

[a_Vivaldi]

a_Vivaldi, great results! Excellent growth rate! What are you using to fertilize them? And what will you call the same hybrids produced in 2034?))

Thanks! I've been impressed by these seedlings so far, hoping they'll be useful for later breeding.

I hopefully won't be making the same crosses again in ten years, but if I do, I'll just call them CT34. I give precedence to whatever crosses I make first, so if I did a Changsha x Tango in 2034, for example, since "C", "T", and 4 are already taken, I'd call it something like ChTa34.

[Lauta_hibrid]

even US-119, which is monofoliate, is 1/4 trifoliate..

Clearly I don't even pay attention to the trees in my own yard... US-119 is a mixed leaf form variety.

How hardy is this plant? I'm mixing Clemenules x Morton and wanted to get an idea of what might happen.

[a_Vivaldi]

I don't know yet, I haven't tested it. I've heard US-119 isn't very hardy though. Clemnules x Morton I think would be hardier. US-119 is 50% Succory Orange, which is not at all hardy. Clemnules is at least a little bit hardy.

[Solko]

Those are beautiful results. Thank you for sharing the pictures as well. I am starting to make some crosses myself and have some first and second year seedlings growing. I’m trying to figure out how to distinguish crosses among these seedlings from the nucellar ones. The info from this forum is great, but from text I never really know precisely what to look for. Your pictures show really clearly the differences among seedlings at different stages of development. That’s very helpful.

I have zero expectations of hardiness from this cross. At best, mid-teens. However, I suspect I'll get something close to 50/50 plants with zygotic seed which will make backcrossing with trifoliate hybrids easier.

Do you have a particular thought or reason to suspect these seedlings will have that percentage of seedlings that will produce zygotic seed in turn? Does Thomasville have a parent that produces zygotic seed?

[a_Vivaldi]

I have zero expectations of hardiness from this cross. At best, mid-teens. However, I suspect I'll get something close to 50/50 plants with zygotic seed which will make backcrossing with trifoliate hybrids easier.

Do you have a particular thought or reason to suspect these seedlings will have that percentage of seedlings that will produce zygotic seed in turn? Does Thomasville have a parent that produces zygotic seed?

My recollection is that Thomasville's female parent was one of the zygotic kumquats. I could be wrong about that though.