I'll need to look at app rate - and I suppose different prills are different in qty per volume. I suppose the nursery does need to -JUICE- them up forsale. But for example, the 5G pot, 2/3 of the top was all prills. When I scarified the top, just to make sure where the root flare was, there was more pills already under the 2/3 of prills covering the top layer. Pull the pot plug out and there was more prills on the sides and bottom of the pot...I don't see me being that heavy handed with the prills but I'll need to check the app rate for my own wiki...

Something that surprised me when I started growing somewhat seriously in pots is how much Osmocote the recommended amount is.

I use Osmocote because we get enough rain that the pots can go weeks without needing additional water. I don't want to have to water the pots just because they should be fertilized.

excessive use of time release in pots.. is a function of the usual method of commercial watering.. which is flooding the pots so that all the excess water and ergo.. excess fert is washed out the bottom ...

soooo.. how much you use.. would be dependent on how you water ...

imo ... you can always add more fert.. IF AND WHEN you see an actual need .. but you cant regrow the roots you burn off thru excessive fert salts... and since tree time is counted in decades.. even in a pot.. you may NEVER see any real need ... as compared to say annual or perennials... the usual suspect after a year or 3.. is yellowing .. lack of nitro in the pot ....

ken

ps: learning how time release releases will aid you in furthering your success ... its more along the lines of multiple heavy dumps.. not a little bit every other day or so .. its a function of heat and water.. to melt the gelatin capsules....

Prilled or slow release fertilizers are notwashed out by excessive watering!! They are much too large to wash out easily through drainage holes and since they are temperature activated - water plays a minimal role in triggering a release of the nutrients - the leaching of nutrients by watering is not significant. That's why most SRF's last for an entire growing season. It is a once and done situation.

And do not be mislead by an assumed lack of need for the regular fertilizing of containerized trees. Because most container potting soils are devoid of any nutrients - 'soilless' mixes - the only access containerized plants have to the nutrients essential for healthy growth is via fertilizers supplied by the grower. Trees require these nutrients to the same degree as any other plants and in fact consume them in greater concentrations than smaller plants.

I have been growing trees in containers for many, many years......my oldest is 25 years. They all get fertilized routinely each spring with an SRF (Osmocote Plus) and none have ever shown signs of a nutrient deficiency nor of any excess. It is a very safe and practical method of fertilization.

btw, the watering practices commercial growers of containerized woody plants rarely ever involves "flooding" the pots. Since most of these growers line out the pots in outdoor fields, it is logistically extremely difficult to irrigate by flooding the field. Most receive either drip or overhead irrigation.

FWIW, in many cases the prills one sees in newly purchased containerized woody plants are empty. Temperature has activated the prills to trigger the nutrient release but the empty prill shells can remain present and visible indefinitely.....because they are NOT readily dissolved by water!

I've used a slow release granual for years with great success on anything that grows, especially in pots. No burning, just tons of growth.

If a conventional container planting was capable of feeding the plant via release of nutrients locked up tight in hydrocarbon chains (HCs), it wouldn't be long before the soil biota we depend on to digest organic matter and free nutrients locked in the HCs would turn large soil particles into small soil particles, destroying much of the soil's ability to maintain a healthy water:air ratio as water retention rises with a decrease in particle size. So, for best results, a container substrate should, most importantly, be able of providing a structured root substrate that holds levels or water:air conducive to good root health, The simple reason is, a healthy plant is no more than a dream if we can't maintain healthy root systems. From this, the conclusion is that a wise container grower leaves the idea of "feed the soil to feed the plant" in the garden where it works wonderfully. Conventional container plantings are generally an environment hostile to soil biota, which additionally means their populations tend to boom when conditions are favorable and plummet when they are not. This scenario makes availability of nutrients more sketchy/unreliable, which is why container growers should shoulder the responsibility of providing for their plants' nutritional needs with fertilizer applications. Soluble synthetic fertilizers offer hobby growers the most control and are most reliable.

I stop fertilizing when mean temperatures are above 80* because plant growth usually stalls as soil temps reach those levels and plants more readily take up water with low levels of dissolved solids (salts). I use controlled release products sparingly because their release rate is based primarily on temperature, so in the heat of summer when I want to cut back on TDS (total dissolved solids) levels to facilitate water uptake, controlled release products are pouring it on. For the reason mentioned, Foliage-Pro 9-3-6 is my "go to' fertilizer for almost everything I grow. If I grow an outlier plant that needs something other than a 3:1:2 ratio fertilizer, I supplement the 9-3-6 with ProTeKt 0-0-3 of potash for added K (potassium), or a small amount of 10-52-10 'bloom booster' fertilizer when additional P(hosphorous) is required. It should be noted that users of "bloom booster" products are supplying containerized plants much more phosphorous than their plants want or can use, and that is as limiting as a deficiency. "Bloom booster" type fertilizers with an inordinately high P level also cause antagonistic deficiencies of at least calcium, potassium, copper, zinc, and especially iron. They also promote a synergistic uptake of magnesium at the expense of a reduction in the amount of calcium the plant can absorb.

Very infrequently do hobby growers provide enough nutrition. Most plants, while in growth mode, need fertilizing at least once every fortnight at the production rate suggested on the container. I fertilize weekly at more than 1.5x full strength with Foliage-Pro 9-3-6 with no problems. Don't try to follow that path unless you are watering to beyond the point of soil saturation, which flushes salt build-up from the soil and very importantly (but seldom considered) keeps the ratio of nutrients, each to the others, from becoming badly skewed and causing multiple antagonistic deficiencies just as excess P caused the 5 or 6 issues mentioned. If you're not flushing your soils regularly, there is not much anyone can do to offer guidance insofar as how to go about fertilizing your plants. Incorrect watering puts a wrench in the gears of any fertilizer supplementation program.

Slow release products are ok, but should be incorporated into the medium to prevent hot spots. A "slow release product" doesn't mean Osmocote, that's a controlled release fertilizer. Slow release products are usually granular and look like the fertilizer you might broadcast on the lawn or garden.

The best fertilizer ratio, which will effectively provide appropriate nutrition the highest % of containerized plants, is a 3:1:2 ratio.Examples of 3:1:2 ratio fertilizers commonly found are 24-8-16, 18-6-12, 12-4-8, 9-3-6, others. They supply nutrients in the ratio at which the average plant actually assimilates the provided nutrients, which allows the grower to use less fertilizer product and avoid antagonistic deficiencies due to excesses of one of more nutrients in the soil solution. I won't make it here, but a case can easily be made that use of 1:1:1 ratio fertilizers like 12-12-12, 7-7-7, 5-5-5, etc are ever actually appropriate, used for containerized plants or in landscapes/ gardens. The argument would center on the fact that no plant uses nutrients in a 1:1:1 ratio, making them a poor choice for containers, and anything we apply in the landscape without a soil test doesn't even rise to the level of a SWAG; rather, it's just a WAG.

Al