A conversation with Enrique Castano on Ume

Have you ever heard the way to tell if an ume will bloom?  The leaves of a blooming ume have smooth undersides, and the underside of leaves on an ume that isn’t going to bloom are rough.  For fun, or maybe to torture myself a bit, I decided to try and cature rough leaves on camera.  What do you know, they’re furry…

As contrasted with the leaves from a blooming ume:

Non-blooming shoot has only vegetative buds at the base of furry leaves:

And flower buds appear on either side of vegetative buds:

1 & 3 are flower buds, 2 is a vegetative bud.  Sometimes, oftentimes, ume will produce flower buds, and no vegetative buds, making it a challenge to prune them to keep foliage close to the trunk.  More on that another day.  I’ve been photographing another experiment for the last couple years…but I digress…

Swelling:

Pop!

But I digress again…I got curious about why non-blooming ume leaves were furry and blooming ume were smooth.  Juvenile vs. adult foliage maybe?  It’s not uncommon to have juvenile and adult foliage in other trees…apples change from lobed to smooth as they get to blooming age.  Junipers have juvenile and adult foliage.  I read a post by another ume grower stating he has observed rough and smooth leaves on the same plant.

The best botany book tailored to bonsai is named “Botany for Bonsai” by Enrique Castano.  Click the title to buy it at Stone Lantern. It is a great reference text to have on your shelves.  I decided to ask Enrique if he has any insight on the fuzzy leaf phenomenon, and he not only answered, but was kind enough to allow me to share the discussion here. Enrique is a molecular biologists who is specialized on gene regulation. So the subject is second nature for him.  Not me!

Hi Enrique,

I have been studying and practicing bonsai for over 22 years, and have enjoyed owning your book, Botany for Bonsai, as it is the only one I have found that really addresses the botany side. This is why I am reaching out to you.

I have noticed, and often heard that Japanese Apricot, Prunus mume with rough leaves on the undersides will not produce flower buds at their axil, but smooth-bottomed leaves do. I have 2 ume, a mature one that is smooth-leaved and blooms, and a younger one that produces rough leaves, and does not yet bloom.

Are you familiar with this phenomenon, and if so, can you help explain why this may be the case?

Many thanks!

Brian Van Fleet
Hi Brian,

Thanks for your compliment. With regard to Prunus mume, I only had that tree when I lived in the UK, and they were already quite old so I did not experiment on younger plants from this species in particular. However it is not uncommon to have distinctive features in the leaves between younger plants and older plants. 

From early on, the development of a plant starts with a particular shape of leaves, and this (shape) will change once the tree matures. However this is not necessarily like it ocurrs with animals. And older tree can become young if it is heavily pruned or if the nutrition forces the tree to grow like a young tree. For example adding too much nitrate will increase its growth and it will not produce flowers, since the tree is making leaves for light absorption and growth. When the nutrition is balanced, the trees requirement for growth depends more on the amount of light available (if it has few branches then it will make younger bigger leaves, if it has a mature branching the leaves will grow slower and will be mature) to manage the energy appropriately. 

The difference between mature and young leaves can be minimal or quite dramatic depending on the species. Some species can grow up to 4 different shapes of leaves depending on the maturity. But know that to address how the shape changes; well, that goes into how genes that control the leaf morphology are regulated. Usually this regulation requires what is called transcription factors.  These are proteins that bind to the begining of the genes and activate particular programs, that after a few more steps (if you want I can explain but it is long…) the shape of a leaf is created. Now the regulation of the transcription factors depends on signals that the cells get and some of these signals include phytoregulators that we call hormones, these hormones can be taken from the outside or created denovo on the plant depending on its growth. 

Well hope this helps, let me know if you want a longer version.

Cheers. Enrique

I haven’t gone back for the longer version yet, but I am tempted, as I think I finally internalized the short version!

Thanks Enrique for a great letter!