Peat-free nutrition – what we’ve learnt this year and what next!

As I sit here at 3.45 pm in late December, looking out of the window into the darkening sky, my thoughts are not of the winter to come but of spring heralding a new growing season. I’ve experienced more growing seasons than I care to admit, but my inherent positivity always hopes, and expects a perfect spring; with mild conditions in March and a sunny Easter weekend to start plants growing, and for people to rediscover the joy of flowering plants in their gardens.

Looking back at 2024, the weather told its usual tale – a variable, cool wet start, neither a good or early spring, and a summer that was often wet with temperature and light levels good in parts. The lesson for me is to prepare for a ‘usual year’ not a ‘hope springs eternal’ perfect weather year!

Here in the UK and Ireland, we are experiencing more localised heavy rainfall events and extended periods of wet weather, with the potential to leach nutrients from container plants during active growth periods – when nutrient requirements are high.

As we move towards peat-free and more sustainable growing media, there is a potentially greater risk of plant quality suffering from poor nutrition. A double whammy of growing media materials having a lower nutrient buffering capacity, combined with a greater propensity to lock up N.

I’ve conducted extensive UK peat-free trials looking at the nutrition of container nursery stock. Those that attended our Hort Science Live ‘Peat-Free in Action’ event in July had the opportunity to see the results at first-hand. While of course, N is very important, water-soluble nutrition added at the start – such as calcium nitrate – can be quickly leached. Our trials this year clearly show the benefit of adding controlled forms of N; such as Osmoform High N, a slow-release N for shorter-term crops such as perennials; and the fully coated Osmocote N (5-6 months) for longer terms shrubs. Results from these peat-free trials clearly demonstrate that controlled N leads to greener plants with more shoots and flowers, whereas water soluble N initially gives rise to faster soft growth but is followed by higher leaching and paler growth.

Looking at the core nutrition, typically higher rates of Osmocote are required for top quality plants – this is also true when growing in peat free. Choosing the right longevity can help too. In our increasingly cool summers, an 8-9month Osmocote 5 delivers 25% enhanced release, compared to the same rate of 12-14month Osmocote 5. The same effect as increasing the rate of the 12-14 month Osmocote 5 by 1kg.

Water soluble fertilisers, such as Universol and Peters, can be used for supplementary feeding, but there are few opportunities to apply them to outdoor crops in a cool, wet season. To have a real effect, water solubles need to be applied several times. If applied overhead, it’s worth taking a minute to consider how much of the water carrier reaches the plant pot.

Blending woodfibres

Looking ahead to 2025, I will be exploring the future – when supplies of certain growing media raw materials, such as pine bark and coir, may be in shorter supply. With UK FSC sustainable woodfibre set to have a greater part to play, the trials will look at blends of different Fibagro Advance grades to create mixes with the optimum water air properties. This will involve blending up to four grades of woodfibre, in much the same way as peat grades were blended in the past. The results are very encouraging when combined with a well-balanced nutrition package – including Osmocote N, Osmocote 5 and Micromax Premium trace elements, plus our H2Gro wetting and water management agent.

Employing our Angelaweb 3.0 precision nutrition programme, our skilled team can advise on nutrition packages tailored to individual situations, taking your nursery’s water quality and growing media into account.

Photo Media trial

Turning my attention back to spring, now is a good time to plan ahead to ensure overwintered stock is top dressed with a controlled release high N fertiliser, such as our sticky Osmocote Topdress FT 4-5month in late winter. This will help ensure your plants are looking their best for that perfect spring we are all hoping for.