My Welwitschia mirabilis seedlings are coming into their own after only a year. It’s rather amazing how much growth they have put on. This is what they look like currently:
Welwitschia, March 2012
Compare this with how the same three plants looked not even a year ago in May of 2011:
Welwitschia, May 2011
Going from right to left in the 2012 picture (left to right in the 2011 picture), here are the current leaf lengths (including the leaf tip dieback):
8.25″ and 8.75″ by .75″ wide
8.75″ and 9″ by .6″ wide
5.25″ and 5″ by .3″ wide
I don’t have an explanation for the one runt. It’s growing in exactly the same conditions, so I’m assuming it’s a turn of genetics. On each plant, one leaf is slightly longer than the other. This could very well be attributed to inaccuracy while measuring. However, I noticed that all three were on one side of the pot (the one facing us in the first photo). I’m guess that since the leaves are closer together there, I favored that side when orienting the pot towards the light. It’s hardly a scientific study, but it looks like light and leaf growth are positively correlated.
Here is the development of the stem/caudex:
stem growth
It’s a poorly-focused photo, but you can see how they are starting to get some girth and become woody. The two leaf-like growths between the actual leaves are expanding, even starting to brown at the tips. Supposedly these are truncated axillary buds which continue to expand sideways as the plant grows. They eventually become the woody “disc” between the leaves of mature plants. This is where the cones will arise when the plants decide they want to produce strobili (at least 4 years from now).
Here’s a look at the meristematic section where the stem keeps growing new leaf material. I imagine that this region remains green for the life of the plant since it continually produces new leaf material and must also expand the caudex to accommodate a wider leaf as it grows.
basal meristem
Repotting should be an interesting challenge, especially considering that I have three plants growing in the one pot. Their surprisingly fibrous root systems are quickly filling up the pot, especially the lower half of the soil, and I imagine untangling them will be difficult. I have heard conflicting reports about the taproot and repotting. Some people say it’s crucial to disturb it as little as possible when repotting. Other sources say that the taproot is really only used for support and anchoring purposes in the wild (since there really isn’t any subterranean water for it to absorb) and consequently the taproot is not that crucial in cultivation. One paper in particular claims that even removing up to 90% of the root mass during repotting only causes the plant slight distress.
This is related to the debate about what shape pot Welwitschia prefers. Traditional wisdom an custom say that a deep pot is required to accommodate the taproot. However, several botanical institutions growing welwitschias in permanent heated beds have observed that they grow a wide and shallow system of subsurface roots, presumably to take advantage of any moisture which the daily morning fog of its natural habitat may impart to the top layer of soil. This supports the hypothesis that the taproot is used largely for anchoring and support, rather than as a significant source of water absorption. Many people successfully grow Welwitschia in standard pots. The one I am using is only slightly deeper than a standard pot with the same diameter. The one advantage to a tall, skinny pot is that the long leaves can hang freely down the sides.
When I repot them, I will err on the side of caution, but I’m not anticipating any extreme issues.
Well, I think that about wraps up everything I have to say on Welwitschia for now. Until next time, happy growing!
The Phytophile 