In Inkscape, I want to visually show the time of year that you should use a specific herbicide. I want it to kind of look like this bar graph. I don't know how to describe the shape that I'm looking for, but here's the closest I've been able to come. I want it to be more symmetrical and precise-looking though. I made an ellipse in the middle but I had to use my mouse to shade in the parts that slope downward.
Inserting path effect Power Stroke makes easily a widened piece on a stroke:
You can edit it with the node tool.
It's not at all sure that the effect becomes visible right outside Inkscape, if you do not rasterize nor convert it to ordinary path.
If you want to keep it as SVG and be sure it's known outside Inkscape, apply Path > Object to Path before saving.Then it's like it's drawn with the Pen:
Your second image can be for example a bunch of aligned rectangles. Here they all have blue fill and no stroke: