Can you plant a vegetable garden in pure compost?

by Jim
(Sussex County, DE)

Had a load of compost from a company "Blessing Blends" specializing in organic, high quality compost. What they delivered looked amazing - so after stripping off the sod and laying a layer of about 18 inches of pure compost - I planted. I thought I was going to have the best garden ever!

However, the plants (tomatoes, cabbage, cucumbers) all appear to have not survived after I was out of town for a week just after planting?? The Zucchini looks like it is thriving but does appear to have some yellow tipped leaves.

What happened? Did I make a mistake by planting directly in the compost? Did the compost burn my plants? The depth is such that it is difficult for me to work the contractor's grade (sandy) top soil into the mix as I suspect may have perhaps worked better. Should I amend with another load of high quality top soil and blend the two?? Help!!

The Compost Gardener Answers

Yikes Jim - I'm sorry to hear about your problems with the compost. You are not alone. Many people make the same mistake so thank you very much for your question.

When you get your load of compost it just looks so great it makes the soil you have in your yard look terrible. It's a short step to substituting 100% compost for the soil.

The thing to remember is that the ideal soil only needs about 5% organic matter. The rest of the soil is made up of 45% minerals, that's the ground up parent material, 25% is water and 25% air. That 5% is magic. It''s where the biology that makes soil function lives.

Don't Bring in Topsoil

Your native soil, the soil that was under the sod you removed, is your friend. It needs some TLC and will likely not reach its full potential for a few years but I recommend working with it, not bringing in topsoil.

When I was growing up my family did not compost a thing. Every couple of years they would, at considerable expense, buy topsoil and put it in the garden. The soil always had an off smell to me. I now know that's because it was likely set in a big pile for a long time smothering all the aerobic biology in the soil. Our gardens were just pathetic.

My grandparents did compost and every year just spread a thin layer over the garden. It cost them nothing and their garden was fantastic.

What to Do Now

What I would do now is take off about 12-14 inches of the compost leaving a 4-6 inch layer over the soil. You can use that compost in thin layers as a topdressing for your lawn and in 2-4 inch layers in your garden beds. If you want to set up for a bigger garden you could remove more sod and put the 4-6 inch layer onto that area as well.

Check and see if you have any earthworms. If you do and you are patient - you can let the worms work that compost into the soil for you. They are brilliant cultivators.

How to Plant Now

When you are planting seeds, pull the compost away and plant the seeds into the soil. Don't cover with the compost - just leave it to the sides.

With transplants do the same. Pull the compost away, loosen up the soil and plant your plants into the soil. Again, leave the compost a couple of inches away from the stems.

Over the course of this growing season you will find the compost will break down and the worms will be getting busy working it all into your soil.

In the fall you can put a layer of compost - if you haven't already used it all up elsewhere - over the garden beds.

Also, start composting yourself. Homemade compost is really great and while you definitely have too much compost at this moment soon you'll be wanting more.

Good Luck Jim

Thanks so much for your question.

Leslie

Thanks
by: Petie

Thanks for that I am about to get into gardening using a raised bed and I havent a clue as to what I am doing Was considering buyin in some top soil etc and adding compost but your guidance has been very welcome and I will now use the actual soil from my garden.

Some cautions
by: Leslie

Hi Petie, just thought I'd make sure you have those raised beds right on top of the soil rather than as separate containers.

When you have containers which some raised beds are you need to make a substantial portion of the soil that fills them compost or other organic matter. It's quite weird but straight soil in a container soon turns into something close to cement.

Probably somewhere around 30% compost would do the trick.

If you are simply adding a bottomless container surrounding your raised bed then do use your soil but still add a good bit of compost.

Good luck and if you have more questions ask away or use the Contact me page so I can reply direct to your emal.

Leslie