Do I really need potting mix?
Recently I was about to go buy some potting mix when our car broke down. There were a few options. I could haul a 40 litre bag plus 20kg child home from the garden centre in the bike trailer. Or I could make my own.
With spring in full swing here in the Southern Hemisphere, many people ask me what soil to use for sowing and potting on seedlings. Do you need to buy special potting mix? The answer is yes and no. So read on to find out what we use, what to avoid and how to make your own budget friendly soil medium at home.
What are my options?
When sowing seeds or re-potting plants, the best soil medium to use is either seed raising or potting mix. You can buy these commercially. With so many different kinds of potting mix available at your local garden store it’s easy to get confused. Don’t worry. There are really only two types of commercial mix we bother to buy. Seed Raising Mix and Potting Mix.
Seed Raising mix vs Potting mix
Commercial Seed raising mix is a custom soil made from bark fines, coco fibre and fine pumice depending on the brand. It is free-draining, fine grade and suitable for germinating seed. Potting mix differs from seed raising mix in that it is more course and contains more slow-release fertilisers. It is an excellent choice once your seeds have germinated and you wish to move them to bigger pots. You can use potting mix as a replacement for seed raising mix or if you need a more economical option. Just sieve it first to remove the larger pieces of bark which could hamper germination of finer seed.
Do not buy cheap potting mix
Be aware of potting mix that costs less than $10 for a 40litre bag. The soil is literally lifeless and will do more harm than good. Cheap potting mix is often loaded with chemicals including fungicides which kill beneficial soil microbes. I bought some once and it smelt terrible. It seemed nothing would grow in it. I attempted to revive it by putting my own compost it in but would have been best to to throw it away. Speaking of bad smells from the potting mix bag…
Stand back from the bag
Be careful not to breath in the dust when you open up bags of commercial potting mix as you can expose yourself to a bacteria which causes Legionnaires’ disease. Open bags at arms length, perhaps wear a mask or cover your face with your shirt and do not shake the bag before opening it. Store your potting mix in a cool, dry location and wash hands and clothing when finished.
What we use
Where possible (and when budget allows) I choose a certified organic seed raising or potting mix to give my plants the best start. Many conventional seed raising mixes contain fungicides which kill beneficial soil microbes. Certified organic mixes contain natural fungi which supports soil life and ensures vigorous healthy roots.
Can I use regular soil from my garden to grow seeds?
Garden soil is not an ideal medium to start seeds in. It is heavy and does not drain well, leaving you with waterlogged pots and trays. You will find that it crusts over on the top which doesn’t allow water to soak in. This means you can end up with seeds that don’t germinate due to lack of water, or seeds that rot due to too much!
Garden soil is also full of seeds from your garden so lots of uninvited seeds come up making it hard to see which seeds you have planted.
Try making your own potting mix
I often make potting mix to pot on seedlings or when repotting some of my patio fruit trees. Any of the following ingredients can be used in combination to make your own…
Old commercial seed raising mix or commercial potting mix. This is the best medium to use as a base as it contains pumice which helps with drainage.
Sieved high quality compost – If you have no compost you can use 1/2 sand 1/2 soil and add a cup of worm castings.
Sieved free-draining aerobic soil from your garden. The best soil to use is the leftover you get after double digging so you don’t end up with holes all through your garden.
Builders sand
Vermicast
Solid Fertilisers. These help to give your mix a boost. I use Natures Garden and Calcium. You can also use dry ground up eggshells or seaweed.
Broken down leaf mulch.
How to make it
Here is the recipe for the potting mix I made recently. I use a wheelbarrow to make it up.
40litre bag of old potting mix
1/3 wheelbarrow of home-made compost
1/3 wheelbarrow garden soil
2 cups Natures Garden Fertilisers
1 cup Calcium
A spade load of vermicast
While we tend to use commercial seed raising mix when sowing seeds we stumbled across this great recipe which is definatley worth a try!
Making your own potting mix is fun and saves money. If you are adding your own compost to the mix it will be far superior than anything you buy at the shop…provided your compost is good 😉 For tips on what to sow now check out our Spring Sowing Timely Garden Advice.
Happy seed planting x
‘With only 42-84 years of top soil remaining in the world, learning how to enrich, improve and maintain soil – in a way that is sustainable – is of vital importance if we as a species are to survive’. – John Jeavons.