I grow very heavily in containers......I have dozens of 'em :-) I use a slow release product (Osmocote Plus) only with woody plants - my collection of Japanese maples, dwarf conifers and assorted shrubs. For everything else I use Dyna Gro's Foliage Pro 9-3-6 formulation on a weekly basis. It is a water soluble full range fertilizer, offering all necessary trace elements and micronutrients and NPK in the 3-1-2 ratio virtually all plants prefer. And is highly recommended on the Container Gardening forum.

Steer clear of those who insist on different fertilizers for different proposes. They are unnecessary, could even be detrimental and reflect a misunderstanding of plant nutrient needs and how fertilizers work.

For me, it depends a bit on what type of containerized plants.

I grow a ton of annuals (mostly flowering) in containers outdoors for the summer. I mix in the slow-release fert like Osmocote when I plant them up. Then use a bloom boosting water soluble fertilizer once a week. I really like the Proven Winners water-soluble fertilizer. But if I run out, I use Jack's or Age Old Bloom.

I do also have a few non-flowering plants outdoors at Summer Camp (monstera, jade, holiday cactus, sansevierias, aloes) and they get the same fertilizer every week while they are out there. Once they come back indoors, they will get Foliage Pro.

I use osmocote also.

We use slow release Osmacote in all of our annual containers we have about three dozen large and small containers and this works well all season. With my hostas, we use a different slow release fertilizer. Annuals are planted in pots with soil meant for containers and for the hostas we use a mixture which includes large bark, shredded bark, mushroom compost, Sweet Peet (don't know if you have that in your area), container soil and a slow release fertilizer. I have a couple of very large house plants that spend the summer outside too but I don't do a lot for them .I repot every couple of years to avoid root issues.

be careful about what peeps in warmer zones suggest ... they may not live and garden in your world ... [or info from peeps who dont tell you what zone they are in ... which is a giant problem with the WWW]]

hosta REQUIRE full dormancy... if you fert to late.. they will not proper harden off in fall.. and go dormant properly ... trust me on that ...

time release ferts come in many formulas... 2.. 3.. 4.. 5 months.. and probably longer...

if you apply a 6 month fert in sept your plants will not go dormant naturally.. normally ...

so.. if you insist in spinning the roulette wheel.. then just apply minimal light weight fert that will use itself up in 2 months or so ... like a 10-10-10 ..

host start growing roots in july.. to store energy to emerge next spring... that is when you should have fertd.. one might suggest.. that fert in sept is already too late ...

easiest solution.. get some water sol.. and give each a deep drink right now .. and be done with fert for the rest of the season;.

and just fyi.. time release fert releases based on temps.. so its of no use in early spring.. and will just sit there until june or july.. when temps actually get warm enough.. in out z 5 or 6 ....

i think that covers most of what you need to know ...

ken

btw.. you'd be better off spending time and money figuring out how to winter over your pots.. rather than worrying about fert this time of year...

that would be a new post with a proper title... imo ...

ken

Thank you for your responses! I have a lot of questions!

Gardengal, the Osmocote Plus is a 6 month fertilizer with micronutrients? This is what you use for your Japanese Maples, conifers and shrubs which are in containers? How much of the Dyna Grow do you use each week for your other plants in containers?

Popmama, the Osmocote you use is the Osmocote Plus or regular Osmocote? Is it a six month slow release also?

Lindalana, what is the NPK of Garden Tone? I have never added bone meal or rock phosphate to my pots.

Miles, why use a different slow release for hosta? Your container mix sounds good!

Ken, how would I know if my hostas weren't going dormant properly? What would I see? Also, it seems like it's getting harder and harder to find granular 10/10/10 fertilizer. Maybe because slow release is more popular?

Ken, I remember hearing that slow release only releases the fertilizer at a certain soil temperature. So if applying it in spring, it would be a good idea to do liquid feed until temperatures warm up?

Actually I looked up a couple of articles about slow release. Here is a quote from one: "once the fertilizer has been incorporated, it cannot be changed. In the early spring and late fall, when temperatures are unseasonably warm or cool, the fertilizer may be released too quickly and cause root burn, or dissolve too slowly, causing nutrient deficiencies." This was taken from:

https://www.pthorticulture.com/en/training-center/pros-and-cons-of-using-controlled-release-fertilizers-in-the-greenhouse/

"How much of the Dyna Grow do you use each week for your other plants in containers?"

1/2 tsp per gallon of water. And yes, that is the Osmocote I use for all my woodies in containers, applied once in April

Umm, any fert might not be absorbed by roots if there is reason for it. There is deep deep science used behind stuff like growing tomatoes in Netherlands by climate controlled computer program that look like 22 ft tree loaded with perfect tomatoes from bottom to the top.

http://www.hostalibrary.org/articles/Pots.htm

I use the pink Osmocote which says Plus. I have also used Proven Winners slow release. Their website says it lasts 4 months.

The pink Osmacote helps our outdoor annual containers which get watered every day in the summer. It's been so hot and we haven't had much rain. The containers make it until late August -early September and look great. The slow release fertilizer gives them what they need--we simply don't have time to fertilize each week. Several years ago, I saw an article by a hosta nursery that grew its hostas in pots, I don't remember who it was, but they suggested using a product which is similar to Nutricote with hostas. They didn't mention Nutricote by name, but it was the closest thing I could find on the internet. I started to do that and it's worked well especially with the my hostas. I add it to my container mix for hostas. I know that many people use alfalfa tea but I don't have the time for that. I've planted more hostas in pots and will see how well they do this winter. I am in zone 5B or 6A. Last winter we had extremely cold days and no snow until late January and February. The plants did well in the covered pots so maybe it was the mixture or the fertilizer or how well I covered and stored the pots, who knows?

I guess I can't use the Osmocote 6 month fertilizer outside for my perennials because I have a shorter growing season. If I applied it in May, then if it really did last 6 months, that would mean it would last until November! I could try it with my houseplants, annuals and colocasia. The colocasia loves water so the fertilizer may not last as long in those pots because of all the watering.

Lindalana, the Garden-tone product looks interesting.

Miles, I think Bob Solberg mentioned a good slow release product at Hosta College this year (online). But since I am in Canada, I can't get it. Here is a link to Bob's talk:

https://www.youtube.com/watch?v=WWA3BljVcYY

Osmocote does come in a 4 month. It comes in a green bag.

First, let's make a clear distinction about growing hostas or other perennials in the ground and growing the same plants in containers. The two different growing methods require different approaches and that includes the need and frequency of any fertilization.

In reasonably fertile garden soil, it is rare that any perennials require routine fertilization. Typically, any organic mulch or top dressing will refresh any depleted soil nutrients. I mulch all my planting beds with compost and have never had a need to supply any commercial fertilizers. If I determined I did, Osmocote would not be my choice. It is too expensive for this purpose and it does nothing to improve soil fertility or encourage soil biology. An organically derived fert is a much better choice - by nature they are all slow release and all work to improve soil health, so a much more sustainable approach.

Plants grown in containers DO require frequent fertilization. They are typically grown in a soil-less media that is devoid of nutrients to begin with and the need for frequent watering of containers, especially in summer, leaches or washes out any applied nutes that must be replaced. A SRF like Osmocote works well for this. Nutrient release is triggered by soil temperatures - not watering - so maximum availability during the period of maximum plant growth. And no leaching. The hotter the soil temp, the faster the product releases and is effective for a shorter period of time.

A couple of notes: for containers, I'd use Osmocote Plus. It has a more desirable NPK ratio and contains all other necessary micronutrients and trace elements that the green bag lacks.

Organically derived ferts are inappropriate for containers so skip the Garden Tone 😑 They require significant populations of soil biology to covert into a plant usable form - why they are by nature slow release - and these are just not present in potting soil.

Gardengal, you reminded me that I don't need chemical fertilizers for my garden. The natural way is the best way. I don't have anything great to add to my garden. The best thing I could think of adding is buying bags of composted manure. That product is mixed in with peat I think. So not sure how much compost my garden is actually getting when I use it. I can also get leaf compost from my city for free. Don't know how great that stuff is.

As for outdoor container perennials, Osmocote Plus is out for me because our growing season is shorter. I guess I could use it for my indoor plants? So it would be best to use a product like DynaGrow that has micronutrients and water in once a week. Thanks Gardengal.

I like the idea of using a slow release fertilizer. I found one that is a 3 month formula. Maybe I could use that for my containers and add liquid fertilizer at the beginning of the season (when the slow release hasn't begun to work yet) and maybe at the end of my season if I think the slow release may have been used up already?