Sunday, February 19, 2012

Repotting a Castillon bamboo: lesson learned

Since our backyard is so small, all our running bamboos are confined to containers. Planted in the ground, they would require careful monitoring to ensure that they don’t escape under the fence into a neighbor’s yard. While I do keep a good eye on things, I’d rather not have to worry about potential bamboo problems.

The downside about keeping taller bamboos in containers is that they get pot-bound fairly quickly. To keep them healthy, you need to remove them from the pot every year or so and remove the rhizomes that will invariably have started to circle around the root ball. In addition, potted bamboos need extra watering because a great deal of moisture evaporates through the leaves.

Our potted bamboos are tied into an automatic drip system. It usually runs from April through late October, i.e. during our dry season. In the late fall through early spring, we get enough rain to keep things hydrated. In a normal year, that is. This winter has been exceedingly dry, about 40% of normal. While I’ve manually turned on the drip a few times, I’ve been lax about it lately. I noticed the other day that our Castillon bamboo (Phyllostachys bambusoides ‘Castillon’), a beautiful running bamboo with green-striped golden culms and variegated leaves, is looking parched. Instead of simply watering it, I decided to kill several birds with one stone: remove the bamboo from its current pot, do some rhizome pruning, and move it into a larger pot.

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Phyllostachys bambusoides ‘Castillon’ (in red pot)
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Leaves on the verge of drying out

With my wife’s help, I laid the old pot on its side and then carefully pulled out the bamboo. I expected quite a bit of resistance, and I was shocked by how easily it slid out—and how light it was. It was clear the root ball was almost completely dry.

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Nice roots but not enough moisture
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Rhizomes circling around the pot. I cut them off before replanting the bamboo.

I removed the rhizomes that had encircled the root ball, trimmed off some smaller culms as well as some lower-growing branches, and then plopped the plant into its new pot. After I filled in dirt mixed with slow-release fertilizer, I watered the bamboo thoroughly. Hopefully within a month there will be new leaves to replace the ones that have dried up. Fortunately, bamboos are very forgiving as long as you don’t let them go completely dry.

                                                                                                                                                  
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New pot, new spot
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I’m hoping that in a year or two the new culms will be tall enough to give us added privacy
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What remains after I removed the oldest (and smallest) culms and the lower branches

I’ve definitely learned my lesson. Just because it’s winter and Mother Nature is supposed to provide us with water, we can’t take anything for granted. Gardeners can never allow themselves to become self-complacent!

5 comments:

  1. I've let a few potted bamboos get way too dry before too, but only during the hottest days of the year. In winter though? I too have learned that even a good soaking rain is sometimes not enough for some pots.

    Also, I'm a little concerned about you removing the encircling rhizomes. Unless you know for certain that there are other new rhizomes in the rootball that you did NOT remove, this seems risky. There are a limited number of viable buds on each rhizome, and once those are "used" you won't get any more shoots or rhizomes. I'm assuming you didn't remove *every* rhizome you saw entirely so the plant's probably fine, but it's something to keep in mind.

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    1. No, I didn't remove all the rhizomes, but a good chunk. I only need a few new culms each year, considering there is limited space even in a relatively large pot. I'm sure there are plenty of viable buds left somewhere :-).

      I think bamboos are unique in terms of how much moisture they soak up. I have many other pots, and the soil in those is nowhere near as dry. Regular watering just isn't on my radar in the winter, but it clearly needs to be.

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  2. Job well done! It's not always easy dividing and repotting bamboos but as you've said it's necessary to keep it looking healthy. I occasionally water our potted bamboos even in winter as they are still prone to dessication. Potted bamboos are quite high maintenance aren't they?

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    1. Too much maintenance, I'm beginning to think, at least in smaller pots. But I still love the look, so I'm willing to accept the extra responsibility.

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    2. Plant them in the ground!

      I wonder if doing a pot in pot in the ground would help with moisture retention? (pot in pot would make it easier to remove the plant to check for rhizome escapes).

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