Garden Writing, an uncertain art
One problem with writing about gardens and plants is that there are so few constants.
In food writing, which I have also done, most items are fairly steady (aside from fads, which soon run their course). In your kitchen, you can take a recipe and create a dish from it with reasonable accuracy and with appealing presentation and flavor. Following a few basic rules, you can mix foods and recipes from different cultures and come up with a delectable whole. And you know that your readers can safely pass that recipe on to their children and grandchildren.
But matters are not that easy in the garden. You tell your readers that February is a great time for planting, and your region is hit by unseasonable frosts and snow storms. You write about certain fruits, and the summer turns wet and cold and nothing ripens. Or temperatures soar, a water shortage prevents you from keeping your plants moist, and your garden dries up. You praise a hosta variety, and it develops a virus. A tree you extol becomes the favorite food of a newly imported beetle or fungus. You talk about a plant you hate because you can never get it to grow or bloom, and readers will immediately write to you, telling you how they love this plant, how well it grows and blooms for them, and how they don't understand your problem. They may even tell you that folks with black thumbs shouldn't be allowed to write about gardening.
What all this adds up to is that garden writing is highly uncertain and thus -- potentially -- very exciting, but it can also be hard on the writer's ego.