Is now a good time? Should I wait a few more weeks? Is it better in spring or autumn? What fertilizers should I use? These are the myriad of questions that come up when people discover you’re a gardener.
When to fertilize is one of the most important questions to ask when you’re first setting out into the gardening frontier. The answer, however, can only be given when it’s been put in context. I want to fertilize …my lawn, …my roses, …my blueberry shrubs, or ….my tropical orchids.
The key to knowing when to fertilize your plants and/or garden is at least understanding the growing cycle of plants. [Disclaimer: To those who haven't already guessed I'm no horticulturalist, so I can't - even if I wanted to - use big horticultural words. I have opted for more common terms and I hope that helps] First the plant goes through a growth stage. It starts as a seed or cutting and begins to grow.
As it grows it transitions through to the fruiting stage where it produces something: either fruit, a flower or a seed pod. At the end of the fruiting stage it either dies (as in the case of annuals) or it goes into the dormant stage.
That’s basically it. Each stage has its own requirements and they need certain chemical elements to aid their particular phase.
- Growth Stage – When plants grow they require more nitrogen and phosphorous. Nitrogen encourages leafy growth and helps plants grow their stems and branches. It is used up readily and usually won’t remain in the soil longer than 12months. On the other hand, phosphorous is needed for seed germination and root development. This chemical will remain in the soil for up to 3 years.
- Fruiting Stage – As a plant enters the fruiting stage it seeks out a generous dose of potassium. Potassium is needed because it helps plants produce fruit and flowers and aids resistance to disease and pests.
- Dormant Stage – The dormant stage literally means the plants become ‘dormant’. They go into hibernation much like a winterized bear. Therefore, they don’t require much in the way of fertilizing.
So the question really shouldn’t be, Is spring or autumn the best time to fertilize? It should be, What stage is this particular plant in and what will it need?
For example, most bulbs flower in spring but begin growing in late autumn and early winter. Roses on the other hand are dormant for most of winter and begin growing in spring to flower later in that season or in early summer. Both bulbs and roses need different fertilizers at different times.
So while most TV shows, especially the adverts of large garden stores, promote a general all-purpose fertilizer these are predominantly useless. What’s the point of plowing nitrogen-rich fertilizer into the soil at the start of a plants dormant period? By the time plant needs it, most of the fertilizer will have leached away.
When to fertilize your lawn
I have already answered the question of when to fertilize lawn on my other blog. In a nutshell, it follows the same conventions as discussed previously.
Nitrogen and phosphorous at the start of spring (it’s growth stage). Potassium in summer for resiliency – not for seed production. More phosphorous in autumn and winter in the form of a slow-release fertilizer.
Photo source: woodleywonderworks