Pot Size & Growth Rate

[Neofolis]

I have heard it mentioned several times that palms that are slightly under potted grow faster.  Having been a fan of over potting, I decided to test this theory with my Dypsis onilahensis seedlings.  This is not very scientific, there are insufficient plants to give any conclusive evidence of anything and it is only one species, so it says nothing about palms in general.

Below is a picture of four Dypsis onilahensis, as featured in my One year later thread.  I re-potted three of the palms, when I usually would and left the fourth in it's root trainer.  Of the three that were re-potted, two were kept in the highest light levels I have in my polytunnel and the third was in more shade.

This is the result.

The two at the back were grown in reasonable light and are clearly much larger than the two in front.  The one in the larger pot of the two in front was the one grown in shade, smaller,but still much larger than the one next to it, still in it's root trainer.

There was another of the re-potted shade grown palms, which was the same size as the shade grown palm in the picture, but it was re-homed a few months ago with my Father-In-Law.

I appreciate that with so few plants in the experiment, the growth or lack of growth could be genetic, but it is still quite interesting to see how much difference there is between plants from the same seed batch grown in different conditions.

[Gbarce]

From what I understand from underpotting one of the benefits is that it allows a young plant to anchor itself firmly earlier because the roots would reach the inside of the pot faster.  This is in particular reference to Anthuriums and Bromeliads  though but in a limited sense it could also apply to palms I guess.

Another benefit I can think of is that if the roots are compacted and localized in a small area when you apply fertilizer to the soil the absorption of the nutrients is more efficient because all the roots are in the same area.

But over all the more room the roots have to grow in the stronger/faster the plant  can grow.

[Neofolis]

As I understand it, the theory behind under potting is that once the roots have "filled" the available pot space, they will slow down their growth and more energy will be devoted to top growth.

[BS Man about Palms]

Corey, I think its also relative to the "step size".  I suspect possibly different results if you went from the liner to a 5 gal size.

[Tassie_Troy1971]

IMO it all depends on the palm for example Howea forsteriana  hate being overpotted and tend to slow down and having a small kentia in a large pot could lead to overwatering as there arent  enough roots to absorbe the water (especially in cooler months) The Kentia will survive for a long while in one pot. They like to be slightly "pot bound". If there are roots growing through the drain holes then you could look at repotting. The diameter of the new pot is most important.  You should only increase this by no more than 30-50mm (1"-3").  The depth of the pot will not matter however the Kentia does not like to be "over potted". http://www.kentia-elite.com/care.htm  

But with washingtonia robusta leave them really rootbound and they struggle to grow at all .

[chris.oz]

I think it is difficult to manage the moisture content of the mix in under potted palms.  The medium in the bottom of the pot may tend to stay very wet, because there is a lack of roots to pull moisture out.   Thus the soil may lack oxygen and the palm will not like  it at all.

[Neofolis]

I have found in the past, with other species, that, if they are left in a small pot, the medium becomes too compressed, due to the prior root growth, and moisture control becomes very difficult, as well as the roots not wanting to absorb nutrients.  Major lack of oxygenation can also occur.  I experienced this with very rooty palms though, like Phoenix canariensis and Jubaea, also with my Macrozamia moorei.  In each case growth stopped then health declined.  Maybe they were just left too long in the undersized pots and maybe the medium was more the issue than the pot size.  There are always so many variables to consider.

[Logolight]

I would think the smaller pot would allow the soil to maintain a higher temperature throughout the pot promoting better root growth.

[Arecaceus]

It totally depends on the palm in my experience. T. takil seems to grow faster in under potted conditions. CIDPs grow much much slower and Washingtonias seem to randomly die if not repotted or planted out soon enough. I think the purpose is also important. If you want a long term pot plant a much bigger pot makes more sense. If you just want to get a seedling over the winter or the next two to plant it out later, under potting is probably better.