For a visual reminder of why soil matters so much to the health and vigor of plants, see the two photos below. These are identical sunflower plants. I planted them on the same day late in the spring. The plants are located less than 20 feet apart in identical full-sun exposure. Why are some of the sunflowers only waist-high, while others are over my head? One word: Dirt.
The short sunflowers are planted in the little meadow between our yard and the path around the city storm-water drainage ponds. I’ve never improved that soil — it’s just what the city and the builder left behind after building our house. It is, as soil scientists might say, lean.
The tall sunflowers were planted on the edge of my vegetable garden. A few years ago, a load of landscaper’s black dirt was dumped there for use in another garden. I didn’t need all the dirt I ordered, so I left it there. This spring, I installed a lasagna garden for planting tomatoes, a rich mix of dirt and compost. The soil near that bed is very close to garden perfection: well-drained, humus-filled soil.
Not every plant thrives in rich soil — nasturtiums, sedum, and many herbs prefer a slightly lean soil — however, if you’re plants aren’t as tall or robust as you would like, consider giving your dirt a boost.