Fertilzers selection for me is easy. I never use them for succulents⦠so far, after 15 years (some plants in the same pot that whole time) have not regretted it⦠yet.

Like wheat and barley, sunflowers are annual plants, the natural rhythms of which and to the greatest extent are controlled by day length. Technically it's the length of the dark period, but that's a different topic. As the nights grow longer, the plant ultimately moves toward death. Sunflowers ripen and die in the same manner as wheat and barley, as do all other annual plants; so, while what you're seeing might be a cultural problem, it's also true you might be witnessing the natural senescence that besets all annual plants, because it's THAT time of year in the northern hemisphere. BTW, what is a boron-based fertilizer? Boron is a micro nutrient essential to normal plant growth and development, but it is used by plants in amounts so minuscule I can't imagine a fertilizer based on it. Al

I think you will find that many who grow houseplants or other containerized plants fertilize their plants with every watering (or at least weekly) during the primary growing season. It is what is called a "maintenance" application and yes, is done at a pretty dilute rate (typically called out on the package labeling). The reason for the frequency is due to the frequent watering required that flushes out nutrients, which then need replacement. This is best accomplished with a very freely draining potting soil so the soil does not stay overly wet between waterings. And this is highly desirable even without concern for the need for fertilization, as an excessively moisture retentive or wet potting mix typically leads to an assortment of plant problems including, but not limited to, root rots. I assume you are located in the UK since you use the term 'compost' for your potting mix :-) Can you describe what it is comprised of? Perhaps we can make suggestions to improve its ability to drain rapidly and fully.

......needs to be amended to remove the cross-post to the New to Gardening FAQ. Posting to any FAQ forum prevents any responses from showing up. They are reference forums, not discussion forums, which is why they are separated from all the other gardening forums.