Put an organic fertilizer on the top and stay away from Miracle Grow. Can also use fish emulsion, seaweed etc. Soil is a living structure, so you want to keep it alive. http://www.homedepot.com/p/Jobe-s-Organic-4-lb-Granular-All-Purpose-Fertilizer-09526/205750607

Sorry, but container soil is not a living system :-)) It is almost entirely inert. And a dry organic fertilizer is pretty much a wasted effort as there are little, if any, of the necessary populations of soil microbiology present to process the dry organics into a plant usable form. Miracle Gro is a perfectly adequate and efficient fertilizer for any container planting although it is short on any micronutrients.

The most permanent potting mix I know of is pumice+peat moss+ sand+ some sifted loam or the best soil you can find plus a little charcoal from the fireplace or fire pit ( discard the ashes ). You can actually grow plants in sand if you water enough. Regular potting mixes made from composted tree parts start to turn to muck after a few months and take your plants with it as the roots rot in the decomposing material. The potting mixes are only formulated to last 4-6 months. If you use your own soil, you will get the symbiotic fungus that plants need. Then you can watch potted plants thrive instead of decline.

LOL!! The above couldn't be further from the experiences of most long time container gardeners!! And is almost directly opposed to the concepts expressed by the literature supporting recommended potting mixes. A quick perusal of the Container Gardening forum would also confirm that the vast majority of successful container gardeners believe otherwise as well. There IS a science behind a properly constructed potting soil that responds directly to the very specialized requirements of growing in a container and it really should be understood and appreciated for its substance.

hey rob, as you can see this is a hot topic. The main problem with old potting mix is that as it breaks down it becomes more like the dirt in your yard - it holds a lot of water, but does not drain well and pots may stop draining and drown the plants. In a no-rain hot climate this may not be an issue, plants adapt well to many growing conditions.

Potting mixes never contained a lot of nutrients, so you always need to add something - compost, fertilizer, whatever you like. If your plants are still growing well enough, then don't worry about it.

My thought for this year would be to add some coarse compost to the top of your pots and try to dig it in where you can without damaging your plants.

Old potting mixes actually de gas- evaporate. Most fake soils do. Its why you see roof top planters that are huge and old..1' or more below the lip of the container. The Oakland Museum has that problem.

I almost never reuse the soils. Only if the pot had some growers superior mix- long lasting things like sand and some loam. Plants I bought from Hawaii at HD for example- when killed off by frost- I noticed could be reused with adding some new fresh soils after I removed the dead root system.

But some mix like Miracle Grow? One and done.

There are two categories, soil based and soil-less potting media. Soil-less versions having nothing there to keep things going after the organic components break down. If kept moist they start to turn into muck, at which point aeration becomes inadequate.

Give it a test run.

Pot#1. Best potting soil you can buy

Pot#2. Permanent mix or Sandy loam with no composted tree parts

See what happens after a year. Which plants did better. They both start out great but as the potting soil ages the oxygen content decreases so root health declines. I watched this happen every year to me. I tried the experiment in almost all sand. Plants grow with no problems. They don't need dead tree and they don't want dead tree around their roots. Dead tree is a cheap material to sell and light to ship.

The growers that plant in ground up composted wood know their plants are going to have problems months later. They tell the nursery or big box store to get rid of them before then. watering becomes tricky then. To help keep the mix from rotting too fast you need to let the mix almost dry out before you water again. This stresses the plant. Plants like cool, even moisture and oxygen at the root zone. Some of the 5 gallon shrubs will die a year or two later after planting. The roots continue to decline in the rotting mix. Adding ground up tree amendment to the hole only makes it worse. Sometimes you can carefully shake the grower's tree compost off the roots and replace it with mineral soil and plants will be fine after a few weeks in the shade adjusting.

I know this is controversial. The nurseries sell the mix and schools teach these practices but it is not what the plants want. ( a NASA guy told us this when they researched what plants want for the space station ) They want to be in a mineral soil with the organic matter breaking down on top. A study was done of undisturbed natural soils in a variety of locations. The organic matter found in the soil was all living. Roots, fungi, bacteria, worms, etc. Not dead tree bark branches and leaves. That stuff is on the top of the soil and fungal networks break it down so the plants can use it.

What kitty is describing are known in the UK as John Innes Compost mixes 1-3

Compost is a term roughly equvalent to potting mix.

the ingredients- peat sand and loam with fertilizer added. The key item being the loam - despite some 50? Years of growing things I am not entirely sure what the English loam is like.

John Jeavons also describes a soil mix which uses lots of compost- screened from the pile. But this is for flats of seedlings , not long term use in a pot.

open bottom pots can use straight soil from the garden as they are just a tiny raised bed. So the hole at the bottom is really what determines how we grow things. Plants are adaptable, there is no one way.

Another thing to consider

Plants dont grow well when surrounded by their own dead roots. The fine dead roots of last year's crop will discourage the same kind of plants the next year. If youre going to plant the same thing again, you need to remove the soil and replace it or plant another kind of plant for 3 or 4 years. Some plants like penstemons will only grow for so long in the same spot and then start to decline. Moving them to a new spot rejuvenates them. I would like to see a list for plants that are like this. A tree expert told me that trees expand their roots into new locations constantly in search of fresh soil for this reason. When a tree cannot continue its expansion, it begins to decline.

There is a guy who told us how his job on the citrus research ranch was to dig out a big amount of soil when they removed a tree and switch it with the middle of the dirt road going around the ranch. Then they would be able to plant the new citrus in the same spot. The tree would reach the outer section of the big hole full of replaced soil in about 3 years. By that time all the old tree feeder roots had decomposed. Weeks roses let their rose growing fields grow other crops for 3 years before replanting roses. My friend had a bed of 15 year old roses that were looking bad. We pulled out the roses and switched out all the soil in the bed and then planted new roses. He had tried replacing one or 2 plants but using the same soil and they did not grow fast even with good food and enough water. They are doing well in the new soil we took from the lawn. The lawn is doing well on the old rose soil.

I just listen and try out these ideas and see if they work.

Weird I ask for peer reviewed research when I hear someone tell me something like that. But that's just me. I don't like being a slave to old wives tales.

I have to say that after several decades as a professional horticulturist, a nurseryperson and a serious and longterm container gardener and instructor, most of what kittymoonbeam has posted is simply NOT borne out by experience or the literature. I don't how to be anymore blunt than that..........it is just very inaccurate.

Yes, all my books say to do something different and that is what is taught at the University now. Nurseries want to sell soil amendments made of ground up trees. This is recent practice. Nurseries used to sell plants in soil in burlap or bareroot or potted in real soil. I was following along with the modern method but now I am doing it the old way and I like the results better. I like not watching my Camellias and Gardenias die off slowly as they used to. I can water my pots every day without fear of root rot now and the plants are greener. Everyone do what you think is best. I'm happy to have found some solutions to problems that no one could help me with. They just wanted to sell me a new plant in composted wood and more "topsoil" which wasn't really soil at all. When that one is dead, I can buy another or give up. I'm happy to have found some people who could help me at last.

Thanks Kitty. Sounds like you know what you are doing!