A little about seeds
Seeds are made up of two major parts. Firstly the embryo which includes the roots and the shoots. Secondly the food source. Seeds are so bloody clever they pack their own lunches!
It also explains why seeds and grains are energy-dense sources of food for us big brained mammals. To grow, seeds need to absorb around 60% of their body weight in water. Additionally they also need access to air. So when growing seeds it’s a balance between moisture holding growing mediums while also having excellent drainage. You can assist the water absorbing process by pre-soaking your seeds before planting for a day or so. Soaking below are some purple king climbing beans.
I tend to only pre-soak large seeds as smaller seeds are too fiddly.
Direct in garden or seed raising mix?
For root vegetables (carrots, beetroot, parsnips etc.) I’ll always sow directly as the large tap root is susceptible to damage when transplanting. Peas, beans and corn I’ll also usually sow direct – the large seeds making it a straight forward process. Most other herbs, brassicas (think cabbages, broccoli asian greens) tomatoes, capsicums, cucumbers…well pretty much everything else, I grow into seedlings before transplanting.
How deep to plant?
It is very tempting to plant seeds deeper than they need to be. While working for the Stephanie Alexander Kitchen Garden Foundation, I found kids always wanted to plant the seeds far too deeply. It certainly seems to be our default setting. Generally speaking seeds are planted to the depth of their width. So broad beans around 1cm while lettuce and cabbage seeds barely need covering. I dare you to simply spread some lettuce seed across the surface of some seed raising mix and just water without covering. In around 10 days they’ll germinate and anchor themselves nicely. We all know how wonderfully weeds grow, and nobody is sowing them at a specific depth.
Caring for seedlings and feeding
Seeds germinate well in dappled light (especially in summer) and this will also prevent the seed raising mix drying out too much. You will know it’s too shady if seedlings grow ‘leggy’ i.e. thin and tall. Temperature is the other necessary factor in germination, with most seeds only coming to life when the soil temp is close to 20 degrees. Professional seedling producers use heat pads to artificially raise the temperature of the soil, leading to subtropical growth in temperate climates.
Use a fine spray of water initially as you don’t want to move the seeds with large drops of water while they’re trying to take root. A hand-held pump sprayer is perfect. As mentioned above the seed provides the required nutrition to germinate but once growing a weak liquid feed is a good idea every 10 days using worm juice or a seaweed concentrate.
Where to source seeds
Here are some links to seed providers who specialise in heirloom or old variety open pollinated varieties. This means you can save the seed year to year and your plants will turn out true to type – something not always possible when saving seed from hybrid plants common in nurseries.
Seed raising mix recipe
Most of these ingredients are readily available at good nurseries or landscaping suppliers (river sand and loam) and will save you lots of money if you’re propagating a lot of your own seeds.
One part river sand
1/2 part vermiculite (this is a naturally forming mineral that is a great insulator and holds moisture)
1/2 part weed free garden loam
1/2 part compost
Handful of blood and bone fertiliser
Mix together and keep in a sealed bucket. Moisten before use.
Remember you can re-use this seed raising mix after planting out your seedlings by adding it to your next batch – don’t throw it out!