The Art of Creating the Perfect Seed Bed

Friday, March 12, 2010 by Jeremy Dore - Categories: organic gardening seeds
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Kitchen gardening has undergone a revolution over the past decade as garden companies, keen to exploit the resurgence of interest in healthy home-grown vegetables, have pushed the idea of ‘convenience gardening’.  This has led to some strange excesses such as the recent expose by Gardening Which magazine that found carrot plug-plants being sold at £1.09 each ($1.60) – more than a whole bunch of organic carrots would normally cost.  There is definitely a place for plug plants and convenience but sometimes the traditional methods are worth reviving and the art of creating a seedbed is one of those methods definitely worth learning.

A seedbed is a small area of the garden set aside for raising tender young plants for transplanting to other areas.  There are several advantages to this:

• The seedlings take up less room while small, so the rest of the garden can be used for other purposes while they are developing (or can be covered with cardboard sheeting or mulch to keep down weeds).
• The seedbed can start off plants while other parts of the garden have vegetables waiting to mature to harvest.  Once harvested, the seedlings can be transplanted, giving them a head-start for succession planting.
• Seedbeds are less effort than starting everything in pots.  I still start early warm-season crops like tomatoes and peppers in pots so they can easily be moved indoors if a late frost occurs but for other cool-season vegetables a seedbed can be perfect.

Of course there are certain crops that don’t like being transplanted and are always sown where they will mature.  This includes most root crops such as carrots, parsnips, beetroot etc.  Brassicas (the cabbage family), on the other hand, are often recommended to be started in a seedbed and, if you are careful when transplanting them, it can even benefit them by causing a better root-system to form as the initial tap-root is broken.

The Ideal Location for Seedlings

It is tempting to locate a seedbed in a corner of the garden where nothing else grows.  However, it is better to give these young plants the best spot – if you fail to give them a good start then there will be little point in all the effort you put in to growing them later in the year as they won’t recover.  So, choose a light position, not exposed to harsh winds but not overshadowed either.  Most importantly the area should be free of perennial weeds and it’s worth avoiding areas where potatoes were grown in the previous year as leftover tubers can send up shoots that uproot seedlings.

Seedbeds can also be prepared in a greenhouse or polytunnel (known as a hoop house for our US readers) as illustrated in the pictures of my own greenhouse.  This is especially useful if you are also using the seedbed to produce earlier plantings although being at ground level the air temperature will always be lower than pots up on a greenhouse bench.

Preparing a ‘Fine Tilth’

A ‘fine tilth’ is a gardener’s term for the perfect soil structure for seeds.  The soil should be crumbly but not dusty, a bit like course breadcrumbs to handle.  This is where most of the effort comes in and how you go about preparing the perfect tilth will largely depend on the soil type you have:

• Sandy soils will need plenty of organic matter mixed in such as sifted compost so that they can retain moisture well.
• Heavy clay or silt soils will need breaking up and either adding fine organic matter or mixing with lighter sandy soil can help to achieve this.  You should avoid trying to prepare a tilth if the soil is still sticky due to wet weather – it needs to dry out first.  Equally, very dusty soil is bad as it will just form a hard crust after rain which is not helpful to young plants.

Most textbooks recommend using a rake to break up the soil after picking through it to remove all stones, weeds and old plant debris (which can harbour disease spores).  You certainly don’t need to dig the ground because the young seedlings will only have shallow root systems and digging just brings weed seeds to the surface.  Likewise, the soil will not need to be enriched unless you plan to also grow plants on to maturity in the bed.

My personal method for getting a perfect seedbed is a little different:

• Pick out any weeds and debris from the surface of the bed.
• Mix together good crumbly compost with extra soil if required in a wheelbarrow.
• Use a garden sieve to shake this, a spade-full at a time, onto the surface of the soil to a depth of about 10cm (4 in).  A good garden sieve has a mesh of quarter inch holes and high sides so you can shake the soil through without it spilling over the sides.  Don’t put too much soil in at a time or it will take longer.
• Finish off with a rake to smooth the soil level so that water does not run off it but soaks in evenly.  I find the back of the rake is more useful for this job than the normal prongs.  Never tread on the soil as you want it to remain light, not compacted.

The final step is to make the seedbed ‘stale’ – a strange term that refers to leaving the seedbed for at least 10 days before sowing to prevent flying pests like onion fly and bean seed fly from causing problems as they are attracted to the smell of freshly disturbed soil. I usually leave the seedbed a little longer so that any remaining weed seeds can germinate and be pulled up before I sow the seeds I want.

Extra Care and Attention

A seedbed should be viewed as the garden nursery and like young children, the seedlings are going to need extra care and attention to help them thrive.  The last thing I do after the bed has been prepared is place a beer-filled trap to get rid of any slugs that are just waiting to devour young seedlings.  In fact, this year I found slugs over-wintering under my slug trap just to avoid me!  Likewise, the area should be netted if cats, birds or other wildlife are likely to disturb it since they often like to use freshly prepared soil. 

It may seem like a lot of work but there is much satisfaction to be gained from getting the perfect ground for your precious seeds.  A seedbed is a valuable addition to any productive garden and creating one is truly an art worth mastering.