Containers & Compost

[Gerald51]

I've got a large compost pile going this year which is made up primarily of tree leaves and lawn clippings to use in my raised bed. I will be mixing some of that compost in with the existing garden soil.

In my containers I thought I would try something different this year, instead of using the usual potting mix. So, what if anything should I add to the compost to make it suitable to put into containers to grow tomatoes?

Will it be too heavy? What's the PH?

Gerald

[johno]

My compost is heavier on oak leaves than grass clippings, but I'll tell you my observations. When I used typical peat/perlite based potting soil in half the containers, and compost/loam in the other half, the tomatoes grown in the peat based mix were about 30% stronger. I expected the opposite from everything I've read. It would have been better to use sharp sand instead of loam (which was probably too heavy). I was just looking for a mix I could make with on-site materials.

You can get litmus paper from the drug store and check the pH, but compost is close to neutral.

[Gerald51]

Thanks for the info. Yeah, most of my compost is oak leaves to.

I'm trying find a good container mix to use all that compost that I have.

I read something about using sharp sand, compost, lime,and peat moss mix, but I don't if you need to add fertilizer to that mix or not and if so how much?

Gerald

[decius]

For many years I have used a mix of 1/3 home-made compost (grass clippings, leaves (mostly pear), kitchen waste, etc.), 1/3 peat moss, 1/3 perlite and had great success growing tomatoes and other veggies in containers. Perlite opens up the mix much more than sand does - that is what you want for growing in containers.

Elizabeth

[Gerald51]

decius,

Why the peat moss and not just 2/3rds compost and 1/3rd perlite?

Gerald

[decius]

Peat moss to lighten the mix and to help water retention. Also, in reality, it helps bulk out the mix if you are always short of compost. If I was going to skip the peat moss I would do 1/2 compost, 1/2 perlite. You want to keep the soil from compacting. It is amazing how much the mix will pack down in one growing season.

Elizabeth

[creister]

Another soil reciepe I found and will try this year:

40% coir fiber
40% compost
10% expanded shale
10% mix of greensand, lava sand, and alfalfa meal

If you go to dirtdoctor.com, that is where I found the reciepe, under potting soil in the library. Howard Garrett does a great job of explaining the use of coconut coir as opposed to peat moss. Once again, I will try this mix this year, so have no personal experience.

[Gerald51]

Is perlite expensive?

I plan on using some 18 gallon sterilite containers (from Walmart $5) to grow a few of my tomato plants in, but the majority of them will be grown in the ground.

Why does container soil mix need to be lighter than the dirt in the garden or raised beds to grow tomatoes?

[decius]

creister- I've used coir and I love it; unfortunately I have never found it in large (i.e. economical) packages. I got a huge bale of peat moss years ago and am still using it.

Gerald51 - Perlite is expensive unless you buy it in very large bags. I get 20 pound bags (and 20 pounds is a lot of perlite!) from a hydroponics store.

Container soil needs to be porous so that roots can get oxygen; since the roots are restricted they can't move very far in search of oxygen and nutrients. Ground soil needs to be reasonably porous too. Ask me how I know - I live in an area where the soil is hard clay; I grow many things in pots because I have not finished amending the soil in all the planting beds so that things will grow decently in the ground.

Elizabeth

[creister]

Elizabeth,

I found a website called originalmulchblock.com where you can buy 6 cu. ft. for 29.99. If you have an Ace hardware to ship to, there is no shipping charge. That is the cheapest I have found it so far.

[feldon30]

I've used 30-40% compost and had good results.

[Gerald51]

Originally Posted by feldon30

I've used 30-40% compost and had good results.

What was in the other 60-70% of your mix?

[feldon30]

60% Pro-Mix, which is now impossible to find in Houston.

$12 for 4 cubic feet of uberpremium, very fine potting mix was impossible to beat.


Also about 10% shredded pine bark just for drainage and to stretch the Pro-Mix.

[creister]

Home Depot in Abilene has dropped Promix from there inventory. That sucks.

[decius]

Thanks creister for the info, and I have an Ace Hardware nearby.

Elizabeth