allelopathic means that it exudes chemical substances from the roots which keep other plants from growing near it:
Black walnut is a prime example of this. In addition to its leaves, black walnut trees store allelopathic properties within their buds, nut hulls, and roots. The chemical responsible for its toxicity, called Juglone, remains in the soil around the tree and is most potent at the drip line, though the roots can spread out well beyond this. Plants most susceptible to the black walnut’s toxicity include nightshade plants (tomatoes, peppers, eggplants, potatoes), azaleas, pines, and birch trees.
https://www.gardeningknowhow.com/garden- ... plants.htm
However, even without that, that looks like a very unfavorable spot. It is surrounded by big old roots, which if they are alive are sucking all the water and nutrients out of the soil. Even if they are dead, they may be taking nitrogen out of the soil as they decompose. It is near a wall, which probably shades it a lot of the day. It is jammed in next to a black plastic thing which may shade it, may heat up in the sun, and certainly cramps the root space, and the soil looks very hard and barren. (As imafan notes nothing else is growing there - if soil won't grow weeds, it is very bad soil indeed!).
If you would like to grow the little shrub, I would dig it out, digging as deeply as you can and getting all the roots you possibly can. If the soil is too hard to dig in, watering it well helps. Then plant the little shrub in a large container (e.g. 20 gallon size) in good soil. Put the container in a sunny spot (if the shrub has been shaded a lot, you will need to move it in to the sun gradually, so it can adapt) and take good care of it for a year or two. Then you should have a big, healthy, thriving shrub you can plant back in the landscape in a more favorable location.
