A pocket wilderness in the heart of Houston.

West 11 Street Park

Tour Stop 9: New Growth Pine

New growth Loblolly Pines







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As you walk through this small grove of young Loblolly Pines, you may wonder why other types of trees don't seem to grow here. It is no accident. The pine trees are actually altering their environment to their own advantage and keeping other species out.

New growth Loblolly Pines New growth Loblolly Pines

Plants need air, sunlight, water, and nutrients to grow, and there is a limited supply of these resources in the forest habitat. Birds or squirrels can move to another location if they run short of food or water, but trees are fixed in place.   So, these pine trees use a strategy called "allelopathy" to discourage anything else from growing around them and competing for the available resources.

Loblolly Pine

Do you see the thick carpet of pine needles underneath the trees? This thick covering serves to prevent light from hitting the ground around the trees, but it does much more. As the needles decompose, they increase the acidity of the soil, making it difficult for many plants to grow. The needles, as well as pinecones from the tree, may also trigger additional chemical reactions to discourage competition. When the pine trees grow taller, even less light can reach the ground, further limiting the growth of competing plants.

Small trees under pines

But look even closer.  There are a few small trees under the pines, including some oaks and Sweet Gums. These small trees have big, light-gathering leaves that help them survive in shaded areas.  They will not get much bigger as long as the pine trees tower over them because they do not get enough light and have to struggle to get nutrients.  But under the ground, they are growing a foundation of roots, ready to start growing tall if anything should happen to the pine trees above them, thus letting light through.

Allelopathy is found in many plants, including Black Walnut trees, sunflowers, and Tree of Heaven – a very invasive non- native plant that also grows in the park.


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