What compost to use in the Harvster for propagation?

If you take a trip to your local garden centre or even the local supermarket, you will find a wide range of compost that you can buy to raise and grow your plants in.  This doesn’t make life easy for any grower and the brands can come and go quickly too. The key to success is selecting the right compost for the right tasks and whether you are growing in a coldframe, mini greenhouse or something larger, the principles are the same.  Here we are talking about raising plants.

The growing medium which you use is highly important to the seeds, plant and cuttings that you are wanting to grow.  What you are trying to do, in essence, is mirror the natural conditions for that plant and it will grow away much happier and more productively as a result.  There, therefore are three basic types of compost that you will find to use; Loam based compost, Peat Based Compost and Peat Free compost.  Each has their particular uses when growing new plants.

Loam Based Compost

Loam based is just a technical term for a soil based compost.  Normally it has a bit of horticultural sand and some peat added in for additional fertility.  This is a firm compost, designed to hold the plants growing in place and at the same time allow excess water to drain freely away.   This is great for hardwood cuttings, semi ripe cuttings and plants like pelargoniums.

Peat Based Compost

Secondly there are Peat Based composts. Essentially these are good for growing plants but not so good for the environment from which the peat is taken.  Peat is very near universal as it is a very good compost that retains water and provides a good basis for seeds to grow from, and softwood cuttings to root in.  This compost is excellent for anything that likes a good level of moisture as this can be a problem inside a mini greenhouse, poly-tunnel or even indoors which is naturally drier than outdoors.  Its disadvantages are that it holds onto a lot of water and can cause seed or seedlings/young plants to ‘damp/rot off’ or fail to germinate due to the high moisture levels so watch out for this.  You will need to take the time of year into account in your watering cycles, watering less in winter than you would in the summer.

Peat Free Composts

The alternative is a peat free compost, the quality of which has markedly improved over the last few years.  This is a mixture of base organic elements particular to each manufacturer and can include bark, coconut fibre, green compost as well as sand or grit to open out the material overall.  The moisture retention in most of these composts is very good and almost equal to that of the peat based composts and so are equally as good for the same applications as the peat based composts.

After that there are plenty of choices about what to do in terms of dressing the top of your see trays of cutting pots.  Personally I don’t use vermiculite on any of my trays of cuttings or seed and find that they normally work quite adequately without that support but others I know insist that this is the way to go.  Vermiculite topped trays and pots tend to stop splashes of compost hitting the cuttings or moving the seed surround in the container and I found with gentle watering that this isn’t a problem.  What is important is using the right compost for the right job and wherever you plant, coldframe, mini greenhouse, Harvster or elsewhere compost choice is really important.