So, you have been to the garden centre a bought your £3.80 bag of multi purpose compost. Here’s how to upgrade it to a professional grade growing media.
The following additives will dramatically improve the quality of your potted plants and have the added benefit of improving your environmental impact by making the peat content go much further.
Controlled Release Fertiliser (CRF)
This is a no-brainer, mix 400g of CRF per 100 litres of compost and there will be no need to add any more nutrients for up to 12 months. Do not mix it into seed and cuttings compost, potting compost only.
Be careful what you buy, CRF (controlled release fertiliser) and slow release fertiliser are two very different products but are often confused.
CRF is is a granule of fertiliser covered by a semi-permeable resin coating making a prill. These prills release fertiliser into the growing medium over a predetermined period of time, usually 6, 8 or 12 months.
A slow release fertiliser is either a granule that takes time to dissolve or it is in a form that needs to be metabolised in the soil before it becomes available to the plant. This group usually lasts 2-4 weeks before needing to be reapplied.
Composted Bark
Add up to 20% by volume for potting and seed compost, 50% by volume for cuttings compost.
The benefits of composted bark in your potting compost are many and not to be underestimated:
- Improves the structure of your compost.
- Aids transmission of of nutrients from the compost to the plant.
- Helps prevent soil borne diseases such as Pythium (damping off) and Phytophthora.
- Improves the water holding capacity, you can water less.
Don’t confuse composted bark with bark chip mulch, composted bark is much finer.
Vermiculite
Vermiculite is particularly beneficial in seed and cuttings compost and compost for small pots, 1 litre and below.
Mix up to 50% by volume for seed and cuttings compost, 25% for potting compost.
- Improves water holding capacity.
- Aids rewetting of dry compost
- Helps retention and availability of nutrients.
If you upgrade your garden centre bag of multi-purpose with the above additives you will see a marked improvement in the quality of your potted plants.