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Which? Best Composts - 2015


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#1 Anonymiss

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Posted 26 April 2015 - 12:57 AM

Best composts for raising young plants

Best Buy composts for sowing seeds and raising young plants

Verve Multipurpose Peat-free Compost (12-litre bag)

best_buy_verve_peat_free_multipurpose_15

Test score, sowing seeds: 70%
Test score, raising young plants: 88%
Peat content: 0%
Price per litre: 15p
Where to buy: B&Q

This contains 80% composted bark, a peat alternative which seems to work well. In the sowing-seeds test, germination was high and the seedlings were strong and healthy.

Make sure you buy the 12-litre bag, as the compost in the other bag sizes is a different formulation that we have not tested.

Levington Original Multipurpose Compost

best_buy_levington_multi_purpose_150_390

Test score, sowing seeds: 70%
Test score, raising young plants: 70%
Peat content: 80%
Price per litre: 14p
Where to buy: garden centres. Levington

At 80% peat, this has one of the highest peat contents in our trial this year. Peat is controversial because of the damage that its extraction can do to important wildlife habitats.

This compost produced consistently good young plants and had excellent germination rates in the seed-sowing test, producing seedlings that were strong and healthy.


Best Buy composts for sowing seeds

Westland Jack's Magic All Purpose Compost

best_buy_westland_jacks_magic_150_390373

Test score: 73%
Peat content: 95%
Price per litre: 12.5p
Where to buy: garden centres

This has the highest peat content in this test and also contains sharp sand, a classic seed-sowing mix. Large numbers of both pansies and tomatoes germinated and grew well.

It was almost a Best Buy in the raising young plants test, but the basil plants were good rather than outstanding.

Westland Multipurpose Compost with John Innes

best_buy_westland_multi_purpose_with_joh

Test score: 70%
Peat content: 73%
Price per litre: 20p
Where to buy: garden centres

This is a peat-rich compost, with sharp sand and grit, but with some wood fibre, too, which can increase drainage. This compost had excellent results for the number of seeds to germinate and the seedlings were large.

In the raising young plants test, it produced plants that you would not be disappointed with.


Best Buy composts for raising young plants

Miracle-Gro All Purpose Enriched Compost

best_buy_miracle_gro_all_purpose_enriche

Test score: 95%
Peat content: 50%
Price per litre: 25p
Where to buy: garden centres

This compost gave excellent results in the basil and pelargonium tests, achieving an almost perfect score. However, this compost did much less well in the sowing-seeds test, just a few marks above the Don't Buy cut-off point, so we would not recommend that you use it as an ‘all purpose' compost, despite the name.

Growise Multipurpose Compost

best_buy_growise_multipurpose_150_390511

Test score: 75%
Peat content: not stated
Price per litre: 11p
Where to buy: widely available

This compost did particularly well in the pelargonium test. Almost every pot achieved excellent scores for colour, size and quality. The basil plants were mostly among the best in the trial, although they needed more water than those in other composts.

Scores for seed sowing were respectable, but not outstanding.

Miracle-Gro Peat-free All Purpose Enriched Compost

best_buy_miracle_gro_peat_free_all_purpo

Test score: 70%
Peat content: 0%
Price per litre: 12p
Where to buy: garden centres

It's heartening to see a peat-free product doing well. It produced large, high-quality basil and pelargonium plants.

This could not be replicated in the seed-sowing tests, however, with very disappointing overall results in the pansy test. Many of the tomato seedlings germinated, but did not thrive.

Verve Sowing and Cutting Compost (12-litre bag)

best_buy_verve_sowing_and_cutting_150_39

Test score: 70%
Peat content: 75%
Price per litre: 31p
Where to buy: B&Q

A Best Buy for the third year running, this sowing and cuttings compost grew consistently good basil and pelargonium plants.

There are two sizes of bag: 12 litres, which we tested this year, and 50 litres, which we didn’t. The two bag sizes contain different compost formulations.
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#2 Anonymiss

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Posted 26 April 2015 - 12:57 AM

Best Buy composts for container plants

Fertile Fibre Multipurpose Compost

fertile_fibre_bb_398040.jpg

Test Score: 86%
Peat content: 0%
Price per litre: 27p (60-litre bag)
Where to buy: fertilefibre.com

This peat-free compost is based around coir, a by-product of coconut production.

The sunpatiens were vigorous and flowered well from early in the season. the potatoes had healthy skins and, although they were mostly small, the crop was the heaviest in our test.

Melcourt Sylvagrow

melcourt_sylvagrow_bb_398049.jpg

Test score: 84%
Peat content: 0%
Price per litre: 32p (50-litre bag)
Where to buy: garden centres

This peat-free compost has been widely used by commercial growers and is now available to the home gardener. It is made from composted fine conifer bark, wood fibre and coir.

The sunpatiens grew fast and were among the first to flower. The score was near perfect in our August assessment and they were still impressive by mid-October. We also grew a heavy crop of good-looking potatoes.

Levington Original Multipurpose Compost

levington_original_multi_purpose_bb_3980

Test score: 71%
Peat content: 80%
Price per litre: 14p (50-litre bag)
Where to buy: garden centres. Levington.

This peat-based compost was a Best Buy in both our other compost tests for sowing seed and raising young plants, making this the best-performing compost this year and one that you can use for all your compost needs.

It produced excellent bedding plants, which had good foliage colour and scored among the highest marks at each of our three assessments through the summer. The potato yield was high, although two of the 12 pots suffered from scab, probably caused by the hot, dry weather during our tests.
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#3 Anonymiss

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Posted 26 April 2015 - 12:58 AM

Worst composts for raising young plants

Don't Buy compost for sowing seeds and raising young plants

Homebase John Innes No.1 Seedling Compost

dont_buy_homebase_john_innes_no1_150_390

Test score, sowing seeds: 35%
Test score, raising young plants: 38%
Peat content: 44%
Price per litre: 24p

This Homebase compost felt heavy and overly sandy. It set hard around the roots, which would make it tricky to prick out the seedlings.

Germination was relatively low in the sowing-seeds test, and both the tomato seedlings and basil plants received low marks for quality.

Alan Titchmarsh and Waitrose Peat-Free Compost

dont_buy_waitrose_alan_titchmarsh_150_39

Test score, sowing seeds: 35%
Test score, raising young plants: 30%
Peat content: 0%
Price per litre: 12p

The tomato seeds germinated well, but failed to thrive. The pansies were generally small and many had purple leaves, indicating a nutrient imbalance.

The basil plants were tall, but pale and weak, while the pelargoniums were generally poor and barely grew in one batch of compost.


Don't Buy compost for sowing seeds

Gro-Sure Seed & Cutting Compost

dont_buy_westland_gro_sure_seed_and_cutt

Test score: 20%
Peat content: 88%
Price per litre: 17p

This peat-rich compost had a very low germination rate for the tomato seeds. It scored the lowest marks of any compost in this test. In five of the 12 pots there were an average of only 11 seedlings, and these were discoloured and weak.

The pansy seeds grew marginally better, but we were still disappointed with the results.
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#4 Anonymiss

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Posted 26 April 2015 - 12:59 AM

Don't Buy composts for raising young plants

Gro-Sure Peat-free All Purpose Compost with Four-month Feed

dont_buy_westland_gro_sure_all_purpose_p

Test score: 38%
Peat content: 0%
Price per litre: 20p

We look for consistency, but both the pelargoniums and basil plants were very variable and disappointing. Overall, most of the basil plants were spindly and there was some scorching at the leaf tips.

A few of the pelargoniums grew into good plants but most were poor, suggesting a nutrient problem.

Gro-Sure All Purpose Compost with Four-month Feed

dont_buy_westland_gro_sure_all_purpose_1

Test score: 38%
Peat content: 50%
Price per litre: 20p

Most of the basil plants were stunted, with the leaves yellowing between the veins and dying off in patches.

Our independent assessor felt this might have been due to the controlled-release fertiliser breaking down too quickly, leading to excessively high nutrient levels that can be damaging to young plants, as it burns the roots.

Dalefoot Wool Compost for Seeds

dont_buy_wool_compost_for_seeds_150_3905

Test score: 33%
Peat content: 0%
Price per litre: 25p

This peat-free compost uses sheep’s wool (that has not been dipped in insecticide and fungicide), which is claimed to release nitrogen slowly, and milled bracken, a waste product from peatland bog restoration work.

Sadly, this compost failed to shine in either test. The basil was spindly and pale, and the pelargoniums were poor quality.

Verve Grow Your Own Grow Bag

dont_buy_verve_growbag_150_390518.jpg

Test score: 33%
Peat content: 55%
Price per litre: 8p

All four batches produced very different results in both the basil and pelargonium tests.

This may be down to its ingredients. While it has 55% peat, the rest is made up of wood fibre - which makes up more than 30% of the ingredients in many of the Don’t Buy composts - and composted green waste, which has proved inconsistent in the past.

Levington John Innes No.1

dont_buy_levington_john_innes_no1_150_39

Test score: 30%
Peat content: 54%
Price per litre: 25p

This compost produced inconsistent results. The basil plants grew tall, but were pale and spindly. The pelargoniums were also variable, and while one batch was good, others were disappointing.

This compost was only tested for growing-on young plants, as Levington tells us it’s not suitable for sowing seeds.

Waitrose Multipurpose Compost

dont_buy_waitrose_multipurpose_compost_1

Test score: 30%
Peat content: 50%
Price per litre: 10p

Varying results between the two tests plagued this compost. The basil plants, among the worst in the test, were very small, pale, and of a poor quality, suggesting a nutrient deficiency. There were also several plants with scorched or yellowing leaves.

The pelargoniums were mostly healthy, with only a few plants showing problems.

Carbon Gold Gro-Char All Purpose Compost

dont_buy_carbon_gold_150_390515.jpg

Test score: 13%
Peat content: 0%
Price per litre: 45p

None of the pelargoniums grew, and their leaves were often discoloured to pink, yellow or white, suggesting severe problems with nutrient levels. The basil plants were also very disappointing.

It avoided a Don’t Buy for sowing seeds as the tomato seeds germinated well, although subsequently the seedlings did not thrive.

Westland Growbag

dont_buy_westland_growbag_150_390524.jpg

Test score: 13%
Peat content: 70%
Price per litre: 9p

The basil plants grown in this compost were especially disappointing. Most of them received poor or very poor ratings on all measures. The pelargoniums were slightly better, with some satisfactory plants, although the majority were poor or very poor.

This suggests the compost suffered from nutrient deficiencies, although this was particularly pronounced in one batch.
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