At first glance, I thought they were walnuts, still in their green hulls, growing curiously low to the ground. I was looking at unripe oranges from Citrus trifoliata, a native of China.
This plant was a shrub, rather than a tree. Its thorns were impressive.
I couldn’t imagine what an orange tree from Asia was doing in the forest near Panola Mountain. I would guess that a bird brought a seed from someone’s garden to this spot, but that’s only a guess.
I recently came across a blooming kudzu vine deep in the forest. (There are several species within genus Pueraria.) Kudzu vines can grow a foot a day. If you look for information on how this invasive species spreads, you’ll find a lot about how it expands its range vegetatively. You won’t find nearly as much about what kinds of birds and animals are likely to take a seed from one plant and carry it miles to an isolated spot, starting a new vine.
I’d like to know more about how these invasive plants are spread by wildlife.
An article published in 2020 that had a nice review of the literature on invasive species reported these figures:
• Number of invasive species introduced into the United States in the past 100 years: 50,000.
• Annual economic costs: $120 billion.
• Annual economic costs of kudzu alone: $100 million.
“Economic costs” reflect lost productivity and the cost of treating infested land with herbicides. That can be a lengthy process — typically five years in treating commercial timberlands.
I’m not sure that the costs of getting rid of invasive plants are worth it. I’m thinking less about the dollars spent and more about the poisons used.
I’m also leery of laws that can’t be enforced. I don’t think you can compel gardeners to stop growing orange trees from China. I think you might be able to persuade them that growing natives is best.
• Source: Paulina Harron, et. al., “Predicting Kudzu (Pueraria montana) spread and its economic impacts in timber industry: A case study from Oklahoma”; PLoS One. 2020 Mar 16;15(3):e0229835. It’s here:
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