As I was just educated by Mrs. Patty S. this very morning, Citrus trees go through root flush growth during colder months and leaf flushes during warmer months. If you're in WI, then temps in your area have probably dropped enough to get your Meyer working on improving its root network.

And yes, branch growth closely mimics the growth of the roots. This is why it is suggested that if/when you fertilize in-ground citrus trees, you should fertilize from the drip-line (where rainwater drips from the branches) inward. Now how this works on potted plants I'm not sure. I would almost say that a larger diameter pot will result in a larger diameter crown, however, I have seen pictures of Meyer bushes in pots that were much smaller in diameter than their crown. Perhaps Mr. Meyer Mike will chime in and give you a better answer. His knowledge, as I have ascertained, is quite extensive when it comes to this particular plant.

Citrus tends to alternate between periods of root growth and leaf growth. This is generally due to competition for the photosynthetic energy available to the plants. The tree also needs to make sure that it has enough roots to adequately support it's canopy. So it makes sense for the plant to alternate these periods.

As temperatures cool below the optimal (or raise above for that matter) which is about 75-80F the plant will slow down it's growth.

I have not heard that colder weather stimulates root growth. It may simply be that as temperatures decline the soil is slightly warmer than ambient temperatures which allows for better root growth than canopy growth.

In the regions where citrus grow natively and temperatures remain fairly consistent you will see the citrus alternate root / leaf throughout the entire year.

It's great that you are seeing healthy root growth. That probably means you have good things to look forward too. I grow my citrus in ground in the hot desert of Tucson Arizona. During the summers here newly planted young trees mostly just focus on root growth because of the crazy heat!

If you are interested in a scholarly article to back all this up see the attached link.

Here is a link that might be useful: Soil Temperature and Citrus

Well, for us here in S. California, we probaby have a small window of root non-growth, both in the dead of winter and height of summer. That is very interesting reading, Cayden, even if the article is rather old (57 years old). I can't find anything in the "Citrus Industry" volumes that discuss root growth in relation to soil temps. It makes sense of course, with any extreme temperatures, that growth of any kind would be inhibited, as with other plants, as a protective mechanism, but I was always under the impression that root growth occurred during cooler temps. I wonder if it is more a case of less sun, when their might be a natural slowing of photosynthesis during the winter months, thus energies can be directed at root growth?

Patty S.

I believe it more about growth/photosynthesis than other factors; when the tree is in optimal growth mode, the leaves produce enough energy for everything. When the leaf production levels drop, the roots are stimulated to grow in search of more food/energy... it is the reason you don't fertilize immediately when transplanting. It is only after the roots grow that the canopy will then grow again. In my environment, where the tree is always in optimal or near optimal growing conditions, the roots tend to grow fastest only after a canopy flush; maybe to maintain the ratio of 4 to 1 tree to root ... at least for Meyers inground.

Patty,

Lol, yeah that was a fairly old study. Here's a slightly more recent one. It's from 1985 so still 27 years old; but same conclusions.

Caid

Here is a link that might be useful: Annual Root Growth Pattern of Young Citrus Trees in Relation to Shoot Growth, Soil Temperature, and Soil Water Content

BTW, have you guys seen images from "minirhizotrons"? These are devices they stick in the ground and use to take pictures of root growth non-intrusively. They use them for root growth studies like the ones mentioned above. I wish I had one :)

Thanks for the info everyone! It's a very interesting topic to learn about =)

Cayden -

Thanks for the articles those are very interesting reads! Also that "minirhizotron" is pretty cool.

Cayden, you say 'non-intrusively'. I hear, "TURN OFF THAT LIGHT!"

I can tell you from experience that when temps around here drop to the low 50's or lower in the spring and summer by night, my plants wilt severely as the air temps warm up very fast by day, especially in mid summer when temps can rise as much as 20 degrees within an hour early in the a.m.

At this time of the year, when temps are just as cold and colder, they do not wilt at all as temps slowly rise into warmer temperature conditions.

I am thinking it may have a lot to do with the intensity of the sun hitting the leaves, rather than the extreme raipd increase in air temp as the root zone is still much colder than the air mass?

The trees that did 'NOT' wilt are the ones that get more shade than sun in the same conditions.

I do know that my trees do not do a darn thing when temps average lower than the 50's by day and night, but they do continue to grow ever so slowly if night temps are cold but daytimes average above the mid 50's and into the low 70's.

I do get phenominal growth when temps are consistantly above the mid fifties at night and up to the 80's.
Even faster growth when temps are 60's to low 70's by night, and then 80's to low 90's by day.
I wish I could have these temps year round!
I have never thought of when the prime time for root growth is, although the top growth is evident always to me.

This definitly causes one to think/ponder, and I appreciate this thread and everyone's input.

I can't really say for sure what my roots do at any given day, but I can understand and interpet if my plants are happy by how the top growth responds to my care and the temperatures they are subjected to.

Thank you

Leekle2ManE,

A lot of the minirhizotron technologies uses sonar to produce the image. Basically they send out a sound wave and then measure how long it takes for it to bounce back to the source. Different materials affect the speed at which the wave bounces back so they can produce something that looks like a picture of the roots without disturbing too much soil ... no lights involved!

Very cool, cayden. I will have to check this out! So, I find this incredibly interesting. It makes a very big different for me, as to when I should be applying my Phytophthora treatment, which is supposed to be applied during "root growth". Thanks for the updated article. I wish I could find this in a resource book or publication. I was surprised not to be able to find it in the online chapters of the "Citrus Industry".

Patty S.

Patty,

Just emailed you an article of sorts about shoots and roots.

As for the Citrus Industry, I have the 1967 edition from my UCDavis days. I find it authoritative in what it covers, but it just doesn't cover much.

Just to answer the question about a balance between roots and foliage.....roots far exceed the foliage of plants in both surface area and weight. A normal tree, growing in a decent soil, will have a root system that spreads far beyond the canopy (drip line) . The root system can spread two or three times farther than the tree is tall.

That being said, if part of a tree's existing root system is killed or cut, the top may respond by shedding branches. If the damage isn't too severe, however, new roots will very quickly replace the lost ones with energy resources from.....the leaves!

Indeed, we know that "cool soils low in initial fertility are conducive to root-growth,"
something I've picked up from Al (Tapla). When re-potting a tree, or transplanting, as John
mentioned, we want the plant's roots to extend into the new medium and establish themselves.
If the mix/ground is low in nutrients, the roots will be encouraged to search. The key, of course,
is to follow up with nutrients after a sufficient period of root-growth - in most cases, we give the
plant two weeks in a shady protected location, which allows for cooler soil, root development,
and less stress to the foliage - which Meyer Mike discussed in referencing the rapid change
in temperature and light intensity on the leaf versus the container.

This advice is primarily for container citrus/plants, but the cool-soil/root-growth phenomenon
occurs in the Spring in many parts of the world (for in-ground plants).

Josh