Hi Carl
We grow our perennials in pots using well-rotted leaves as the potting mix and fertilize with a non-organic liquid solution about once a month.
We're thinking of switching to slow release fertilizer. The compost is not weed free, but weeding takes surprisingly little time. Pots are very heavy.
We've been using this method for about five years with great success.
I amend occasionally with grit for better drainage for some plants, especially alpines, but most are grown directly in the compost. Some plants, like lewisias, which like really sharp drainage seem to do surprisingly well in compost.
The plants look good and customers really like them. They seem to have better takeoff when planted in the garden. Plants require less water, less fertilizer and have much higher tolerance to occasional abuse. Mostly we notice the difference during drought periods, or by July. When perennials grown in other mediums look bedraggled, ours glow. Customers comment on it frequently.
We overwinter almost all stock outside and survival is astonishingly high. There is a problem in spring though, when the heavy pots can become waterlogged after our snow melt and the plants will emerge, but die off, presumably from lack of oxygen.
We've become adept at grabbing that stock and preparing it for the tables first. Tipping the pots overwinter would probably solve the problem.

Thanks for the response ninamarie - I'm surprised the lewesias grow in such a 'rich' substrate as well! Do you make the leafcompost yourself? If so how long does it take - 2 years?

Chemical slow release fertilisers work well and are probably more respectful environmentally than monthly liquid doses - careful not to overdose though - I always work on the cautious side with most perennials. I'd still like to find an organic alteranive if that exists though.

Carl

I don't believe you really need a "pelletized slow release organic fertilizer", as by definition organic fertilizers are all or mostly slow-release. If you use a good, all-around organic fertilizer, or make up your own from animal and plant meals(cottonseed, alfalfa, blood, and bone meals), plus fish and seaweed emulsions for micronutrients), you should be all set.

For those who do want an organic, round pellet type slow-release fertilizer as a Osmacote/Nuticote substitute, there is a product you can find on-line and elsewhere made of pelletized composted poultry manure. It is advertised as an osmacote substitute.

You might check out your question on the Organics Forum as well.

Here is a simple explanation from the Gardener's Supply catalogue:
"Organic versus Synthetic
Do plants really care where they get their nutrients? Yes, because organic and synthetic fertilizers provide nutrients in different ways. Organic fertilizers are made from naturally occurring mineral deposits and organic material, such as bone or plant meal or composted manure. Synthetic fertilizers are made by chemically processing raw materials.

In general, the nutrients in organic fertilizers are not water soluble and are released to the plants slowly over a period of months or even years. These organic fertilizers stimulate beneficial soil microorganisms and improve the structure of the soil. Soil microbes play an important role in converting organic fertilizers into soluble nutrients that are available to your plants. For this reason, organic fertilizers are best applied in the fall so the nutrients will be available in the spring. In most cases, organic fertilizers and compost will provide all the secondary and micronutrients your plants need.

Synthetic fertilizers are water-soluble and can be taken up by the plant almost immediately. In fact applying too much synthetic fertilizer can damage your plants. Synthetic fertilizers can give plants a quick boost but do little to improve soil texture, stimulate soil life, or improve your soil's long term fertility. Because synthetic fertilizers are highly water soluble, they can also cause problems when the nutrients leach out into streams and ponds.

Synthetic fertilizers do have some advantages in early spring. Because they are water soluble, they are available to plants even when the soil is still cold, before soil microbes begin to work and make nutrients available.

For the long-term health of your garden, feeding your plants by building the soil with organic fertilizers and compost is best. This will give you soil that is rich in organic matter and teeming with microbial life."

Here is a link that might be useful: Commercial slow release organic fertilizer

So far, we have been using compost from the municipal dump. I live in a fairly-well wooded area in agrigultural land in Ontario. Our municipality had set up an informal program in which residents were allowed to dump their leaves. Unfortunately, some also used it as a garbage pile. The compost is excellent quality, though weedy, and well-rotted. Drainage in pure compost is excellent, which is why the lewisias managed, I suppose.
I do pot most alpines in a grit mix.
We have just begun accepting leaves from the municipality to compost here. I can't tell you how long they will take to break down- we have never dealt with a pile of this magnitude before. We will let nature take its course. My only concern is keeping the pile covered as much as possible with something inexpensive and water-permeable. I'd like to keep air-borne weed seed out as much as possible. We lack the equipment to turn the pile often enough to maintain a high enough internal temperature to kill weed seeds.
If anyone has any suggestions, I'd like to hear them.
We've wrestled with fertilzers since the beginning. Most of the organic ones we've tried have been difficult to apply.
Plants mostly seem to like a foliage-flower boost occasionally. Root growth is amazing. I'll check out your suggestions, ginger. Thanks.
Nina

Organic fertlizers may, or may not be slow acting, and by definition "organic" only refer to the source of the material, not its properties. And many of these fertilizers are formed from animal parts, not just naturally occurring mineral deposits and organic materials as stated above. For example, blood meal is much faster acting than many slow release synthetic fertilizer formulations.

True about the blood meal. But generally the feed meals, bone meal, compost, and manures are slower acting than your 50 lb bag of synthetic 10-10-10.
G.

Carl,

I grow cacti and succulents (Including lewisia) using only organic nutrients. I have over the years come up with a mix of alfalfa, kelp and Neem-seed Meals that, with a bit of oyster shell and Amozite (a mineral source of available potash (2.5%) and over 50 trace minerals) that works well as a slow release fertilizer, at least for what I grow.

I have stayed away from animal products (other than the oyster shell) like blood & bone meal mostly because they are too hot for my crops and I have safety concerns... handling cacti means I always have open wounds for mystery bugs and prions to get through the skin.

I mix my nutrient blend in to my custom cactus soil mix and also use it as a top dressing boost in the spring when I re-mulch all the pots with fresh scoria. As an extra boost I will also make a "tea" with it. Using it as needed through out the growing season, but that is usually only needed for heavy feeders like Adenium, Plumaria, Persikia & Lewisia. The tea is enough to keep them in heavy bloom and "selling like hot-cakes."

good luck,

Hap

Thanks, that gives me some ideas to try out this growing season. I need to do some side by side trials to be sure what works and what doesn't.

Regarding the slow release fertilizers, my main concern with organic sources are the relatively ill defined dosage and period of release. I guess experience will show what does and what doesn't work. I don't want to use liquid feed as I'm not setup to dose correctly and don't like the idea of liquid runoff.

Carl

I'm gonna second ginger's suggestion that you re-post the question on the organic forum.

As for an osmocote replacement, you could probably just irrigate with diluted compost teas, depending on your setup.

There are plenty of ideas on organic potting mixes on the website below. Good Luck!

Here is a link that might be useful: Organic potting mixes