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Don't Buy composts for raising young plants

By Adele Dyer

If you buy the wrong compost your plants will struggle to grow and bloom. So avoid these Don't Buy composts for raising young plants.

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Our Don't Buy composts for raising young plants were a real letdown. The plants hardly grew and were stunted, pale and didn't flower. 

Worst composts for raising young plants

Seedlings and small plug plants have delicate roots that need careful nurturing to make sure they grow well. As a result, the perfect compost should have a balanced fertiliser that will gradually give the young plants the right nutrition to grow rapidly. It should also be fine enough for young plants' roots to be firmly nestled in the compost, but be open enough for the water to drain through so plants don't sit in water.

Our best composts for raising young plants have just this mix, but our worst composts were coarse and lumpy with unbalanced fertiliser that stopped the plants' growth in their tracks.  

This year, we grew pepper 'Arianne' and fuchsia 'Shadowdancer Amelie'. Overall, the results were very good, with strong plants produced from most composts. These Don't Buy composts stood out against the rest as they were small and stunted with pale or yellowing leaves.

See how all the composts scored by looking at the full results table, and see which were Best Buy composts for sowing seeds and containers. 

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Compost Our verdict Pepper young plants Fuchsia young plants Score
Compost non-member logo M ** ** 30%

Poor nutrient balance

Peat content: 0%

This green-waste compost had low nitrogen, which is needed for green, leafy growth, but very high chloride levels. Chlorides make it hard for the plant to take up nitrogen. It also had high levels of salts, which can burn a young plant's roots, making it hard for them to take up water and nutrients. 

As a result, the peppers and fuchsias hardly grew in this compost. 

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Compost non-member logo M ** ** 23%

Wet compost with almost no fertiliser

Peat content: 70%

This peat-based compost was let down by one of the four bags we tested. This bag contained very wet compost in which the plants struggled to grow. 

When we analysed the nutrient content, we found it contained almost no nitrogen. It had very low levels of all other major nutrients, leaving the plants severely underfed. 

In this one bag the peppers and fuchsias were among the worse we saw, with hardly any growth by the end of the test. 

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