Gardeners will be unable to buy peat-based compost by 2024, so at long last, we will all be using peat-free products. Manufacturers are constantly improving their composts, but there are still some duffers. I for one rely on Which? Gardening’s annual assessment of the composts. As I show, these rigorous tests can produce unexpected results.

This year, they tested a selection of brands. When testing seed sowing compost, they used ‘Red Alert’ and Petunia ‘Express Gold’. Twice a week they checked how many germinated and after that assessed every week how well they were growing. For young plants they chose tomato ‘Tumbling Tom Red’ and Marigold ‘Tiger Eyes’ and they grew these on for six weeks, assessing their development every week. Both varieties were greedy feeders so the researchers tested how nutritious the different composts were.

Which? Gardening found that Fertile Fibre Original Seed Compost was the best overall performer. A coir, vermiculite and loam mix, it proved every bit as good as peat-based composts. Fertile Fibre Original Multi Purpose took second place. Coir-based with vermiculite and loam added, unlike many multipurpose brands, it included plant feed. Like their seed compost, multipurpose had good germination rates and plants developed well.

Moorland Gold Seed & Cutting compost was next on the roll of honour. It uses peat particles collected from the filters used to purify drinking water. This peat would have to be removed anyway and has not been specially dug, releasing carbon in the process.

Interestingly, Which? recommended gardeners should avoid Dalefoot Wool Compost for Seeds. The mix was too nutritious for petunias to germinate and seedlings were stunted. Even the tomatoes did poorly. Most young veg plants are greedy feeders and need a nutrient-rich compost to grow strongly. If the young plant runs out of nutrients it will slow or stop its growth and may never fully recover. The exceptions are some root vegetables like carrots and parsnips which may lazily keep their developing roots near the surface if they feel little need to grow downwards.

Whatever compost you buy, check how heavy the bag feels: if it has been left out in the rain it will be heavy and have lost much of its nutrient. Don’t buy any compost with a faded label that has clearly been weathered for some time. Old compost changes and does not produce the expected results.

Plant of the week

ANEMONE BLANDA VAR. ROSEA ‘PINK STAR’ does indeed have bright pink star-shaped flowers with a white “eye”. The species is a woodland plant so give Anemone blanda humus-rich but well-drained soil that is fairly dry in summer. Clumps readily spread but the plant is low-growing, 10-20 cm, so best at the front of a border or under roses or shrubs that will not yet be in leaf.

The dark green leaves are attractively divided and last in to the summer to recharge the knobbly tubers.