Once the temperature creeps up over 85F, *most* plants begin to shut down. When the plants are shut down, or slowing activity, they aren't drawing as many nutrients from the potting medium. As such, those nutrients aren't being used, so they simply accumulate in the mix.

I think that's the rationale, but I'm sure Al can explain better.

Josh

Oxboy - I couldn't answer your email because of how you have chosen your user page settings. You can change them or just include your email addy when you write other members.

I stop fertilizing because heat stress decreases roots' ability to function when the plant most needs to move water efficiently. Since the higher the EC/TDS of the soil solution is (the more salts in the soil), the more difficult it is for the plant to take up water, withholding fertilizer during periods when soil temps are 85* plus has served me well. Keep in mind that if the pots are shaded, root temps will often lag ambient temps by up to 15*, while root temps in pots sited in direct sun can easily be 50* higher than ambient temps - one of the reasons that blow-overs in nurseries are such a bane. The unshaded and often black pots have more surface area exposed after the plant has toppled, which can have a devastating impact on roots.

Al

Thanks for the response, Al.

So let me ask your opinion if I may -- if you lived in the dry mid desert like me (40s* night - 60s* day temps during winter) and could keep certain potted perennials like Camellias, Azaleas, etc outside in 5-1-1 during the winter, would you still continue to use Foliage Pro during these months? Or wait until spring?

this is the first time i hear about this.
so i am curious, what about hi-feeders that grow in tropics? like alocasias, etc? they love heat and certainly grow huge in high heat/humidity. and the recommendation is to feed them regularly too. no feed over 85F would not apply then.
i most certainly feed other plants in pots too like amaryllis, coleus, caladiums, petunias,etc that are prolific growers. the summers in my area (NYC) are hot and humid, the temp of over 85F lasts for probably at least 6 weeks if not more.
i am quite sure the growers in fl feed their plants too - considering in south fl they have 85F for most months of the year ! the soil is poor on top of that. they won't be able to get much out without fertilizing.
yes, i know that the main crop growing season in so fl is winter, but there are plenty of plants that still grow in summer too - it's the rainy season after all, when most tropicals put on growth.

"if you lived in the dry mid desert like me (40s* night - 60s* day temps during winter) and could keep certain potted perennials like Camellias, Azaleas, etc outside in 5-1-1 during the winter, would you still continue to use Foliage Pro during these months? Or wait until spring?" I would continue to fertilize with the proviso - you avoid fertilizing with urea-based supplements or organic sources of N (blood meal, feather meal, alfalfa meal, horn meal, fish/seaweed emulsion ..... when mean temps are below 55* to avoid ammonium toxicity, which means that you can use maintenance strength concentrations of FP 9-3-6 regularly if you're able to flush the soil when you water.

Al