Pollinating indoor Meyer lemon

[wwfruit]

For the past several years, my 20-year old Meyer lemon has spent the winter in my Walla Walla, Washington garage.
For the past several years, it has burst into bud about a month after coming into the garage, kept at about 55 degrees, them extravagant bloom.
Alas, it has not set fruit, and my attempts at hand pollination, via paintbrush and pencil tip, have failed.
Has anyone else had success with hand pollination and do you have any advice?
The lemon stays in the garage from about November to March, depending on the weather.

Summary

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[anon47724557]

Meyer lemon needs pollination with another citrus variety. It is not true to seed.

[Dom]

I’m really not sure why your having difficulty, my Meyer lemon is self pollinating. It was completely indoors at one point and I did use a paint brush to increase pollination. Now I move it outside in spring and I assume the bees/ bugs are doing the work. I have no other citrus.

[wwfruit]

It has borne plenty of fruit in the past, but nothing the past two to three years, when all of its blooming has happened in the garage. I think it has previously done some blooming while outside so the bees and other insects were able to do the pollinating. It seems I need to be more diligent about helping it pollinate!

[bopcrane]

I think that could be it! almost all the sources I have found about meyer lemon that mention anything about self compatibility imply lemons are almost all self compatible, though that does not necessarily mean it self-pollinates well indoors without pollinator action.

On a different note, Meyer is definitely mostly monoembryonic and will likely not come true from seed but interestingly enough there have been experiments in the past that have shown it is apparently possible to induce nucellar embryo and callous tissue development in some monembryonic species of citrus, including meyer lemon - apparently through a complex process limiting “recessive genes [that] may synthesise a potent inhibitor of embryogenesis”

from the second link above, regarding growing citrus generally indoors: " Adequate light, moisture, fertilizer, and hand-pollination (indoors) are essential for successful fruit production."

I’ve also read that temperature can impact some parameters of flower compatibility in some citrus species but I have no idea if meyer is sensitive like that or not. Your tree, blooms etc look great in the picture by the way!

Edit: Also wanted to include some other interesting reading, about a bud sport of pomelo that is a self-compatible version of the “original” - so kind of like how variegation or anthocyanin/lycopene production can spontaneously happen when a new sport/mutant is “made”, apparently citrus reproduction is tied to a bunch of genes that can apparently sometimes mutate and flip a switch (the SI gene “switch” that limits self compatibility):

“Self-incompatibility (SI) substantially restricts the yield and quality of citrus. Therefore, breeding and analyzing self-compatible germplasm is of great theoretical and practical significance for citrus. Here, we focus on the mechanism of a self-compatibility mutation in ‘Guiyou No. 1’ pummelo (Citrus maxima), which is a spontaneous mutant of ‘Shatian’ pummelo (Citrus maxima, self-incompatibility). The rate of fruit set and the growth of pollen tubes in the pistil confirmed that a spontaneous mutation in the pistil is responsible for the self-compatibility of ‘Guiyou No. 1’.”

[anon47724557]

Meyer lemon is one of the few lemons not true to seed. It is likely a hybrid of a true lemon and a mandarin. True to seed citrus don’t need pollination, not true do like meyer lemon, pummelo, tangelos and others.

[bopcrane]

That’s true meyer usually does not come true from seed - however most sources clearly state meyer lemon to be self-compatible. As an aside, you mentioned meyer being possibly a lemon x mandarin hybrid, which is interesting and relevant here, as a specific Self-compatibility gene (abbreviated “SC”, as opposed to the self-Incompatibility gene, “SI”) was found to likely originate in mandarins and is why most or at least many mandarin varieties and hybrids are in fact self-fertile.

So, really, some “families” or lineages of citrus, whatever you want to call them, (Swingle vs Tanaka taxonomical system, whether most citrus are truly hybrids and not species, etc.) there are some that are more predisposed to having the SI gene vs the SC gene, but this really does not seem to be a definitive and hard rule - again, the genes here controlling self-incompatibility are apparently mostly recessive and in some instances can even be naturally “switched off” like in the example I gave you with the self-incompatible pomelo variety that had a bud sport that WAS self compatible.

source: “Here, we demonstrate that SI citrus species employ the
S-RNase-based GSI and harbour a S-RNase linked to several SLFs
at each S locus. Notably, we identify a mutant S-RNase, Sm-RNase, that is responsible for SC in citrus; this SI–SC transition occurred first in mandarin and then spread to its hybrids. As citrus is evolutionarily distant from other families that use S-RNase SI, our data provide new insights into the evolution of this widespread SI system.”

“Data from crosses show that SI in citrus is controlled by a single co-dominant S locus with multiple S alleles17,18”

" We present evidence that SI-SC transitions due to the Sm -RNase, initially arose in mandarin, spreading to its hybrids and became fixed."

Edit: I think maybe you might be speaking of parthenocarpy, which is a related mechanism but not the subject of my post. It is very important subject in the production of good quality citrus fruit that are “seedless”. Parthenocarpy is apparently also controlled by sets of genes that can be expressed or suppressed even in grapefruits or pomelos that are usually mostly monoembryonic and self-incompatible. Source

" Considering that about 20.0% of precocious-flowering nucellar seedlings of grapefruit did not set parthenocarpic fruits, it is suggested that the parthenocarpy in these hybrid seedlings of grapefruit are controlled by three dominant complementary genes, P1 , P2 and P3 ."

[bopcrane]

@wwfruit apologies on me leaving out the actual useful and functional info on pollenating meyer lemon! you can refer to this here which has an excellent diagram of citrus flower anatomy a page or two in. It also explains some of the concepts of self-compatibility and incompatibility and some reasons why some citrus may experience poor fruit set.

Pollen viability (and when the anthers will shed that pollen, “anthesis”), AND on the other side of the “fertilization equation” the flower’s stigma’s receptiveness - can be impacted in many ways

One thing I can see recommended by some people with finicky-fruit-setting citrus is to use an electric toothbrush to kind of “buzz” pollenate the flower when you can see the pollen is readily detaching from the anthers of the flower. Hopefully at that time the stigma is receptive and pollen grains will land on it, the pollen is accepted, pollen tube forms + fertilization occurs, then fruit sets and will hopefully hold to maturity. Good luck on your citrus tree!

[wwfruit]

Thank you so much for all the helpful and informative information!
I received my Meyer lemon as a gift in 2000, and it was shipped from Four Winds Growers in California, which specializes in dwarf and small trees for the home grower. I just visited their web site and it looks like all their trees are grafted, though I just went out to look at mine and can’t detect the graft margin.

But I will study the diagram of the citrus flower anatomy (again!) and see if I can help my lemon set some fruit. This morning there are 3 more open blossoms, and I think the “stickiness” factor in being receptive to the pollen is present early on. Paintbrush at the ready!!!

[aap]

I might add that Meyer lemons need more fertilizer than other citrus. They are heavy feeders. Depending on the rootstock, they tend to be small tree’s. Mine is about 5 years old, still very short but wide tree.
Old picture. Tree still same size.

Here is the same tree today.

[wwfruit]

Thanks for the reminder to feed lemons; I think I fed mine shortly before bringing into the garage, just over a month ago.

[aap]

What are you feeding with. High nitro, I hope. If you only have one tree, Osmocote plus, will work. It,s more forgiven, but not perfect. I got about 30 tree’s, my choice fertilizers are different, also larger quantities.
My trees are in a growroom, temps are around 65/72*, led shop lights 12 hours.
Since my tree’s are actively growing I continue to feed them with Osmocote plus till about the end of February. My tree’s stays on Osmocote plus year around with my regular fertilizers.

[Ged]

Your tree looks very healthy, so no reason it shouldn’t set fruit. Mine always has, indoors or out, so much so it usually needs heavy thinning. It may be having trouble with the cool temperature in the garage. I have seen fruit fail to develop after a cold night or two when the fruit is just started. Flowers may fail under similar conditions. In fact, it’s setting fruit now, indoors.

[wwfruit]

Thank you for the encouragement to warm up the garage a little bit! I did open one of the heat vents and put up another light that is adding warmth; will see how it responds!

[aap]

Citrus roots would not do much of anything below 56*. Of your temps stays above 34*in the garage, the tree will lose its leaves, no problem there. Come spring it will take of again like nothing happens.

[wwfruit]

Oh, the garage is in the low to mid 50’s; it typically loses a few leaves, but not a large percentage. Will see what bringing it up a few degrees can do for it!