There is some confusion when it comes to whether you should fertilize your rooftop garden or not. In either case, it’s important to understand when fertilization is applicable to you.
When Not to Fertilize Your Rooftop Garden
Ideally, you should fertilize your rooftop garden rarely, if ever. One of the key characteristics a garden designer takes into account, is the ability for the garden to remain self-sustaining. You can see why regularly adding fertilizer can seem counterproductive to that ideal.
The role of your rooftop garden in controlling storm runoff means that you don’t want any contaminants getting into the water supply. This is especially a problem that can occur if you use a conventional fertilizer. They are dense with nutrients, and your roof won’t absorb all those nutrients before rainwater washes it all away. This is a process called nutrient leaching.
If you’re doing any rainwater harvesting, then you should not use any fertilizer on your roof garden. The fertilizer nutrients will definitely get into the rainwater that you’re collecting. If you plan to use that rainwater for other gardening duties, then it may be okay. But if you’re using it for anything else, then you probably don’t want it contaminated.
When to Fertilize Your Rooftop Garden
You have to handle fertilization on a case-by-case basis. You have to take a few things into consideration.
- The type of plant life growing
- How much maintenance the garden requires
- Whether it’s an extensive or intensive rooftop garden
If you find that your rooftop garden needs fertilizer because it struggles, then you should apply it only once or twice a year at most. In addition, you should always use a controlled release fertilizer.
A good way to go about it is to use fertilizer once at the start of fall, and once at the start of spring during the first year of your garden. After that, you can do it once a year in the spring for a few years. At some point, there should be enough nutrients in your garden for it to sustain itself.
If your rooftop garden is for aesthetic appeal, then you may have to use fertilizer to get many of the flowering plants to grow along with the rest of the garden. This can become a delicate balancing process, so it’s best to speak to a local gardening company about it. Depending on the growth medium, you will need a fertilizer that can benefit the plant while not causing detrimental effects to the other growing things.
