Re-using previous year's potting mixture in containers

garyc1234 · June 18, 2016

Does anyone have advice on re-using a previous year's potting mixture when growing in containers? (The potting mixture was used for growing tomatoes in the past.) Basically, this is to save money on buying new potting mixture every year. (I used Miracle Grow Potting Mixture, and NOT the Moisture Control version).

I'm thinking for a 10 gallon container, 45% new potting mixture, 45% old potting mixture, 10% compost, and a scoop of perlite to help the drainage given the compost and old potting mixture. Then after these are mixed together and tomato plant is in the container, put a ring of TomatoTone fertilizer around the base. (larger containers would use this same ratio)

What do you think?

luigiwu · June 18, 2016

I don't add anything new. I just sort out the old roots and reuse with whatever admendments I want. I think I am on my third year?

drew51 · June 18, 2016

I reuse soil, and what you mention sounds good to me. I usually only add some new soil and some compost, maybe 10%. I use it three years then put it in my raised garden beds. Last year my 2 year old soil performed better than new soil. This year it's about the same. 1,2 and three year soil all performing about the same. Off subject but I'm having the best tomato year ever, yet I have failed to harvest one yet! The reason I say it's going to be good year because the plants are disease free, and usually I start having problems about now. So no doubt production is going to be better.

rnewste · June 18, 2016

I would not add compost to a container mix.

In my containers I use a 3:2:1 ratio of potting mix, microbark chips, and perlite. For second and subsequent years, I discard 1/3 of the old mix along with the rootball, and add in new mix to replace that amount.

Raybo

garyc1234 · June 18, 2016

Thanks to everyone for their advice.

Raybo, is the reason to avoid compost due to drainage issues or that we don't know what nutrients may or may not be in the compost or some other reason? Thanks!

drew51 · June 18, 2016

I like to use compost because a good compost has high levels of Trichoderma harzianum. Which is a fungi that can colonizes plant roots, and attack other fungi, such as the root rot fungus. Compost is often used to prevent root rot in containers.

dmforcier · June 18, 2016

I have used and reused MGPM - the Moisture Control version - for years. Two things: 1) the new product contains time release ferts; you can ignore that or replace with Osmocote or similar. 2) Be careful what you reuse. If a plant dies mysteriously, don't reuse the dirt from the pot: it might contain a disease or fungus. Otherwise just shake out the root ball and discard the part that isn't dirt.

No need for more perlite, but it doesn't hurt. Adding padding like microbark chips doesn't help anything until the average particle size in the pot exceeds a certain amount. Depending on where you are MGPM contains more or less sphagnum, which does degrade over time. Mixing new into the old to fill out the volume will keep it fresh enough for a long time.

All that said, I am slowly transitioning to Fox Farms' Ocean Forest. The plants seem to like it better. Can't tell you yet how reusable it is. Good luck.

Dennis

peppero · June 18, 2016

I use the old with some new and a bit of sand.

Jon

Ed of Somis · June 20, 2016

I have container gardened for many years...and my results are at least as good or better than in-ground plantings. Lots of good ideas above. Old potting mixes are just fine...as long as it has not carried a soil-borne disease from the prior season. Sometimes I "enrich" old mixes....and sometimes not. It is not advisable to use "moisture control" mixes. They contain polymers that hold water...and can make the bottom half of a pot a mucky/waterlogged mess. I actually add up to 1/3rd cactus mix to my pots to fasciitate drainage.

June 18, 2016	#1
garyc1234 Tomatovillian™ Join Date: Mar 2016 Location: Zone 10a (Alameda, CA) Posts: 67	Re-using previous year's potting mixture in containers Does anyone have advice on re-using a previous year's potting mixture when growing in containers? (The potting mixture was used for growing tomatoes in the past.) Basically, this is to save money on buying new potting mixture every year. (I used Miracle Grow Potting Mixture, and NOT the Moisture Control version). I'm thinking for a 10 gallon container, 45% new potting mixture, 45% old potting mixture, 10% compost, and a scoop of perlite to help the drainage given the compost and old potting mixture. Then after these are mixed together and tomato plant is in the container, put a ring of TomatoTone fertilizer around the base. (larger containers would use this same ratio) What do you think?

June 18, 2016	#2
luigiwu Tomatovillian™ Join Date: Jun 2013 Location: ny Posts: 1,219	I don't add anything new. I just sort out the old roots and reuse with whatever admendments I want. I think I am on my third year? __________________ Subirrigated Container gardening (RGGS) in NY, Zone 7!

June 18, 2016	#3
drew51 Tomatovillian™ Join Date: Dec 2013 Location: Sterling Heights, MI Zone 6a/5b Posts: 1,302	I reuse soil, and what you mention sounds good to me. I usually only add some new soil and some compost, maybe 10%. I use it three years then put it in my raised garden beds. Last year my 2 year old soil performed better than new soil. This year it's about the same. 1,2 and three year soil all performing about the same. Off subject but I'm having the best tomato year ever, yet I have failed to harvest one yet! The reason I say it's going to be good year because the plants are disease free, and usually I start having problems about now. So no doubt production is going to be better. Last edited by drew51; June 18, 2016 at 04:55 PM.

June 18, 2016	#4
rnewste Tomatovillian™ Join Date: Apr 2007 Location: Campbell, CA Posts: 4,064	I would not add compost to a container mix. In my containers I use a 3:2:1 ratio of potting mix, microbark chips, and perlite. For second and subsequent years, I discard 1/3 of the old mix along with the rootball, and add in new mix to replace that amount. Raybo

June 18, 2016	#7
dmforcier Tomatovillian™ Join Date: Apr 2016 Location: Dallas, TX Posts: 3,825	I have used and reused MGPM - the Moisture Control version - for years. Two things: 1) the new product contains time release ferts; you can ignore that or replace with Osmocote or similar. 2) Be careful what you reuse. If a plant dies mysteriously, don't reuse the dirt from the pot: it might contain a disease or fungus. Otherwise just shake out the root ball and discard the part that isn't dirt. No need for more perlite, but it doesn't hurt. Adding padding like microbark chips doesn't help anything until the average particle size in the pot exceeds a certain amount. Depending on where you are MGPM contains more or less sphagnum, which does degrade over time. Mixing new into the old to fill out the volume will keep it fresh enough for a long time. All that said, I am slowly transitioning to Fox Farms' Ocean Forest. The plants seem to like it better. Can't tell you yet how reusable it is. Good luck. Dennis

June 18, 2016	#8
peppero Tomatovillian™ Join Date: Jan 2009 Location: selmer, tn Posts: 2,944	I use the old with some new and a bit of sand. Jon

June 20, 2016	#9
Ed of Somis Tomatovillian™ Join Date: Jun 2013 Location: Somis, Ca Posts: 649	I have container gardened for many years...and my results are at least as good or better than in-ground plantings. Lots of good ideas above. Old potting mixes are just fine...as long as it has not carried a soil-borne disease from the prior season. Sometimes I "enrich" old mixes....and sometimes not. It is not advisable to use "moisture control" mixes. They contain polymers that hold water...and can make the bottom half of a pot a mucky/waterlogged mess. I actually add up to 1/3rd cactus mix to my pots to fasciitate drainage.