Most gardeners will use some kind of potting mix in the course of the year, whether it be for starting transplants, growing potted plants or container gardening. Every now and then I need a reminder to avoid cheap potting mix. Years ago I learned the lesson the hard way by having almost all my little tomato and pepper seedlings suddenly fall over and die. The problem was the potting mix I was using. The mix was on sale, as it had sat, in its sacks, in the parking lot of a box store, through the entire winter. It had been wet for months. What I didn’t understand was that such conditions promote the growth of harmful fungi which soon attacked and killed my seedlings. Lesson learned: it’s not good for potting mix to be damp for long periods of time before use.
Old, damp growing medium can be risky because of the risk of fungus.
Another time I used a very economical soil mix for starting seeds. The seeds sprouted and the seedlings made it to a couple inches in height, and then they stopped growing. I was busy and not paying a lot of attention to this fact. I finally noticed when they, too, began to die. The problem: the soil medium had almost no nutrients in it. It’s important to remember that man made soil substitutes need to have nutrients added to them, as their base ingredients usually contain few or none.
Some soil substitutes contain few or no nutrients.
Such a growing medium might be used successfully if the gardener recognizes the deficit and supplements with some kind of liquid fertilizer (fish emulsion, Miracle Grow, etc.) Still, it is nice to start out with a good medium, something that, in itself, will give your plants a good start. Lesson: watch your plants and seedlings. If they turn pale or languish, think about applying some fertilizer.
Farmers Almanac on How to Make Your Own Potting Soil
Seed starting mix is usually very good for starting seeds, but doesn’t sustain prolonged growth. It’s necessary to transplant seedlings into something else within a few weeks. A good quality seed starting mix is very useful. Once I did find a bad quality seed starter. It was much worse than not useful. It killed seedlings. So, do your research before purchasing. I can’t say that I’ve used Burpee’s Seed Starting Mix, as pictured above, but I’d be surprised if it wasn’t good.
Two Tips about Seed Starting Mix:
- It’s good, though not absolutely necessary for starting seeds For starting really small seeds it can be very useful.
- It’s not very good to use for general use with potted plants as it tends to be too light, neither retaining moisture as well. as regular potting mix, nor providing enough physical support for larger plants.
Mixes labeled “Potting Mix” are usually for general purpose use.
This means they may work pretty well for both general seed starting and for growing plants in containers or pots. These mixes usually have a fair amount of peat moss in them, which retains moisture. They’re fairly light, yet retain water easily. If I’m not starting something rare, expensive or especially difficult, I often use “potting mix” to start my seeds. I also use it for growing plants permanently in pots or planters.
Related Post: When Transplants aren’t the Best
Bags labeled as “Garden Soil” do not work well as potting mix.
I grow sweet potato slips (cuttings) every year and sell a fair number of them. Some people start slips in plain water, which is not very good for producing larger quantities of slips. I mistakenly thought that the quality of the mix used for slips didn’t matter. So, this year, when I purchased “potting mix,” I purchased the absolute cheapest. Technically it wasn’t even potting mix. The label read “Garden Soil: For In Ground Use Only.”
For the size of the bag, it was really cheap. And it worked… horribly! My sweet potatoes almost refused to sprout in it and when they did, they barely grew. After waiting for the sweet potato roots to grow slips for two months I purchased some real “Potting Mix” and started repotting my slip producing sweet potato roots. As I unpotted the roots I discovered that the “Garden Soil” didn’t retain moisture very well through much of the container, so the top strata were too dry . It did, however, allow water to puddle at the very bottom. This caused a lot of my starter roots to rot! If the label says “For In Ground Use Only,” pay attention and don’t make my mistake. This soil mix is too high in shredded bark, etc. to retain moisture, as needed in a container.
What about using plain garden soil?
That is the cheapest “potting mix.” Every now and then it works alright, but especially when starting transplants for the garden, I would advise against it. Drainage and moisture retention of plain garden soil are usually not good for containers and pots, which have drastically different needs than growing straight in the ground. Also, plain “dirt” can bring pathogens and pests which, while under control in the ecology of the garden, rapidly spin out of control in a pot or tray. So save yourself some heartache and use a good seed starting mix and/or potting soil.
In closing, here are some some general Tips about potting soil:
- Don’t wet the potting soil before you need it.
- Avoid anything which is really heavy in shredded bark, unless it’s going to be added to the soil already in your garden.
- Don’t trust artificial growing medium to nurture your seedlings for long. Use a supplement.
- Beware of really cheap potting mix, it’s probably cheap for a reason!
Do you have a tip or suggestion about potting soil or seed starting medium? We’d love it if you’d share in the comments’ area below.
Another garden problem dealt with: When Beans Don’t Produce