I recently got a question from a reader about growing a garden in straight compost. Because I think a lot of people make this mistake, I thought I’d share my thoughts in a post.
She writes,
Hi Mavis, I am having a gardening problem I thought you might have some insight on. I have two raised beds. I went to a garden center to buy some soil for these beds. I think I got ripped off…I told the gentleman how big the raised beds were and what I was growing. He sold me 2 cuyds of a compost. When it was delivered the driver was surprised I wasn’t mixing it with anything like top soil. Nobody told me!! I proceeded with putting my garden together. But my transplants don’t seem to be thriving. Can you grow plants in straight compost? Should I fertilize them? I mean even most of my seeds aren’t germinating. I’m so disappointed! Do you have any suggestions?
Sadly, you can’t really grow a garden very successfully in pure compost. It does not create a very balance grow medium that most plants need to survive. Depending on where you got it, it could be way “too hot” {nitrogen rich} for plants to germinate. Also, depending on the make-up of your compost, it can contain a concentrated level of other minerals that are great in small doses, but that are really easy to overdo. In addition, it doesn’t allow for the proper amount of air flow and water retention.
I would recommend pulling up the plants and sticking them in little pots {with potting soil} while you remedy the situation. Now, brace yourself, because the remedy is going to cost you more money and more work. I don’t know how deep you your garden beds are, but I would take at least 6″ of the compost out of there and then mix the remaining with top soil.
This will create a better overall balance for the plants to thrive. When I researched balanced soil for gardening, I found that over and over again, most sites recommended only about 5% of your soil be composed of organic matter {compost}.
If it is too late in the gardening season to re-plant your seedlings after you have remedied the situation, you can always plan for a fall garden. If you are new to gardening, remember that there will be years like this. It is a learning process–and even then, sometimes Mother Nature will kick you in the teeth for no reason whatsoever. Take the time to get your soil right, and by this time next year, you’ll have better luck.
Any other suggestions readers?
~Mavis
You can learn all about compost in this What is Compost and Why is Compost so Important? post I wrote awhile back. You’ll be a compost expert after you’ve read it. Promise.
Erin says
You could also allow the compost to “cool”. Basically just leave everything as is in your beds for 6mo. Rain will leach away the excess nutrients and the ingredients will mellow over time. But you’d have to grow things in pots. You could also try growing specific things to eat up the nutrients, like winter squash or melons. They tend to like compost rich places.
Or you can do what Mavis suggested and the good news is, if you store that compost somewhere, you will use it for your beds eventually as it is important to replace the used nutrients by adding compost in at the end of a growing season.
Marilyn says
My potato grow bag I purchased said to plant my seed potatoes in compost. So I purchased bagged compost and followed the instructions. So far so good. The potato plants are thriving and starting to flower. I’m wondering though if I’ll actually have potatoes to harvest in the end.
Carrie says
I built 6 new raised beds at my new home this spring. I filled them with compost from my city (made from yard waste) and I added 2 bales of peat moss among the 6 beds. I had sporadic germination with the seeds I planted. The transplants that I planted showed no signs of growth for weeks but eventually they started to grow. My reasoning was that the roots were growing first. My zucchinis, cucumbers, eggplant, onions, beans and tomatoes are doing great now. I had good success with starting kale from seed directly in the bed. Carrots, spinach and beets had very low germination rates. I have one beet and 10 carrots going strong and zero spinach but the red oak leaf lettuce and romaine lettuce was good.
My suggestion if you haven’t done anything yet would be to leave the plants and wait and see.
Robin says
The first thing I would do is go back to the garden center, talk to the manager and get some resolution about the fact that you were sold only compost. Someone at the garden center sold you only compost for your garden bed? If you explained that you were a new gardener, they should have known to sell you some topsoil also. They need to have a talk with that staff member. Maybe they would at least be willing to give you some topsoil. Just a thought. Hope things work out better for you next year and like Mavis said it is a learning process, so don’t give up just cause you had one bad year. Good luck.
Mari says
MY GARDEN IS ALL COMPOST…. No soil what so ever. I moved to a new property with just bare clay and stones and knew nothing would grow. So I brought in all the medium for my raised gardens. I started with a layer or pea straw (from harvested peas) then brought in copious amounts of untreated sawdust and lawn grass compost. I added nitrogen rich sheep pellets and blood and bone and planted away. I had an absolutely amazing garden which was producing veges and flowers with in 6 weeks. This mix sank over the summer as the pea straw rotted down so I have added the contents of my compost bins and more of the sawdust/grass compost and have been eating my winter veges all winter. I have had to keep the water up to the gardens in summer but now I have rich soil. My gardens were only developed in Oct last year and I have had both summer and winter veges with amazing crops. My flowers, shrubs and roses are also doing fabulously in the same mix.
It has been years since I have had soil gardens… opting to use compost mixes from the landscape centres until I had enough of my own. I have even had gardens made up completely of raked up leaves land kitchen scraps, left to settle over the winter (in large plastic bags or bins). Good compost forms nutrient rich humus, which real gardeners strive to make use of.
If compost is so bad…. why do plants grow under trees in forests?? They are growing in decayed leaf litter. This is the best, richest soil medium you can possibly use/ This is why so much of the Amazon is being deforested to make use of the rich deep humus. This is how most soil is formed.
Emily E. says
Mari, this is an excellent point. I constantly have volunteer pumpkins, squash, sunflowers, etc. growing out of my compost pile. I think one of the keys is to have the proper proportions of green and brown matter that has been aged appropriately. If you’ve ever dumped a bag of grass cuttings in a pile and forgotten about them for a few days, you’ll be able to smell them and if you move them you can feel the heat! Mari the way you garden sounds like no till gardening from “way back when” or layer gardening. I’ve done a variation of this with very good success. As you mentioned this is how it happens in forests. It sounds like maybe the compost is not equally balanced? Best of luck!
Phyllis says
The problem with ALL new gardens is soil. You’re never going to have good soil until you make it and you have a good start. Mixing the organic matter into the top foot of soil will help a lot. If you don’t till or mix the compost into the soil it will eventually become good growing medium. By next year things should be much better. Even though some people have great success with all compost, it’s important to remember that not all compost is the same quality, and there is a difference between finished compost and shredded organic matter. Luckily, once the organic matter breaks down to finished compost (probably next spring) things should be much better.
In the mean time all those squash, cucumbers, melons, zucchini, should grow well in the organic matter that you currently have.