You feed plants what they need when they need it if the soil the plant is in can't do it.

Many plants don't require fertilizer at all and even prefer 'poor' soils. Others will do great with some compost mixed in and no fertilizer.

Others will only perform best if they get a particular nutrient(s) at a particular time. For those you have to know the plant and it's specific needs for optimal performance.

When a slow release fert says it lasts 4 months it actually says it lasts *up to* 4 months. In reality plants take up nutrients at different rates, soils vary in their ability to hold on to nutrients and weather conditions, such as precipitation and temperature will affect how long the granules take to break down.

I guess what I am saying is there isn't a simple answer to your question ;-)

But, if you are going to be feeding wqith a time release chemical fertilizer, you should have done it when you put the plants in in the spring...
Yoi don't want to force growth that will be killed by frost.
Linda C

thanks so much for the helpful advice everyone!

~bobby

Prilled time release fertilizers like Osmocote are coated with a substance that breaks down at specific temperatures, releasing the nutrients gradually then as the coating dissolves. Generally that is a soil temperature of around 60F, give or take. Applying them in very cold or excessively wet weather can affect the coating also, often destroying it so that the nutrients are released all at once. Prilled ferts are best applied in midspring once temps have moderated and the soil begins to warm and I find they are best used with containerized plants rather than those in the ground - pretty expensive for generalized garden use and generally not warranted. Fertilizer spikes are totally inefficient and I don't recommend their use at all. They are a marketing gimmic rather than any reasonable approach at supplying neeed plant nutrients.

FWIW, organic fertilizer are by nature slow release and feed the soil and encourage necessary beneficial soil organisms and are far less temperature or weather dependent. Much better to provide plants with a natural source of nutrients than chemicals.