Most perennials don’t necessarily need fertilising. However, in some cases, it’s still beneficial to provide them with nutrients to support healthy growth.
With proper nutrition – such as horn shavings – gaps in the perennial bed will fill in more quickly.
Just like vegetables, perennials are divided into light feeders and heavy feeders – meaning some need little to no fertiliser, while others require more nutrients. The group of nutrient-demanding perennials is relatively small and mainly consists of highly cultivated, lush-flowering border perennials like delphinium, phlox, coneflower, and sneezeweed. Many of these species originate from the North American prairies, where they grow in nutrient-rich loess soils.
If your garden soil is sandy, you should apply 2 to 3 litres of mature compost per square metre every spring, mixed with a heaped handful of horn shavings.
Planning a new perennial bed? During soil preparation, it’s also a good idea to work in plenty of well-rotted cow manure.
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Fertilising After Cutting Back for Rebloom
Some early summer bloomers like salvia, delphinium, and others will rebloom later in the season if cut back a hand’s width above the ground right after their main flowering period. This process, known as remontancy, requires a lot of energy from the plant.
To support this, fast-acting nutrients are helpful. An ideal option is a mineral fertiliser like Blaukorn (Blue Granules), as it provides all essential nutrients that the plant can absorb immediately. In garden centres, it is available under the name “Blaukorn Novatec.”
- Apply sparingly – one heaped teaspoon per plant is enough.
- Water the plant afterward to dissolve the fertiliser and make nutrients readily available.
How to Fertilise New Perennial Beds
A newly planted perennial bed or groundcover area may initially appear quite bare – with lots of exposed soil between plants. This bare ground is quickly colonised by weeds, which require frequent weeding in the early years – often a significant maintenance task.
Once the perennials have formed a closed canopy, weed growth will naturally decrease.
To speed up this process:
- After the initial growing phase in June, feed the bed with a fast-acting organic fertiliser such as horn meal or a special perennial fertiliser.
- This is recommended for all types of perennial plantings – whether under shrubs, in a showy perennial bed, or a groundcover area.
In the following years, fertilise in spring until the bed has filled in, using a mix of compost and horn meal.
Humus for Shade-Loving Perennials
Perennials growing in partial or full shade generally have low nutrient needs. However, applying leaf humus in spring acts like a fertiliser – even though it contains very few nutrients.
- Simply spread 3 litres of decomposed autumn leaves per square metre between the plants.
- You’ll notice a visible growth boost, as the new layer of humus encourages the formation of runners and new roots.
