Last updated on October 23rd, 2023 at 08:58 pm
You have carefully created a compost in your garden, which by now has produced ready humus.
And now you’re wondering when to spread compost and how much compost should be spread in the garden?
Here you will learn exactly that and get an overview of the amount of compost that can be applied depending on the plant culture.
Compost should be applied to the garden during the growing season in spring and summer. On average, you can spend 2 liters of compost per square meter per year in the vegetable patch and lawn. Woody plants, such as shrubs or hedges, and perennials tolerate 1-2 liters of compost per m2 per year.
When to apply compost?
Compost should be applied during the growing season in spring and summer, when plants are growing, flowering and thriving.
Despite some still conflicting opinions, this is the recommended time to apply compost, also according to the technical literature and experts, such as the European Federal Environmental Agency or the Weihenstephan-Triesdorf University of Applied Sciences.
During the growing season, plants grow, form flowers and fruits, and therefore also require the most nutrients.
The plants can usefully obtain a large part of this nutrient requirement from compost soil if the compost is spread in the garden at this time.
In principle, compost can be spread in any weather, although rather damp, overcast weather is advantageous. This is because the compost can then be better worked into the soil and is directly available as a source of nutrients for the plants.
When to add compost to the vegetable bed?
Compost should initially be applied to the vegetable bed at the beginning of the growing season, i.e. in spring, either shortly before planting the seedlings or shortly after. During the rest of the growing season through the summer, vegetables should be regularly re-fertilized with compost.
Spreading compost in autumn
Compost should never be applied in the fall because plants absorb little to no nutrients during the cold season, and the risk of soil leaching is highest during this time, so fertilizing with compost would have little effect.
Little to no nutrient uptake by plants in fall and winter.
As mentioned earlier, the growing season for plants, the time when they grow and thrive, is in the spring and summer.
In the fall and winter, however, plants are in what is called vegetative dormancy, a time when they are not growing. Vegetative dormancy is similar to hibernation in animals.
When there is no growth in autumn and winter, no nutrients are needed or absorbed by the plants.
For this reason, the application of compost in the fall is not useful or effective.
Risk of soil leaching in autumn and winter
In addition to plants that are in the garden year-round, there are of course crops, such as vegetables, that are usually harvested completely in late summer.
In this case, the beds lie fallow and without plantings that would have nutrient needs or a solid root system branching out in the soil.
This can result in a compost application in the fall or winter leading to leaching and transfer of nutrients to groundwater.
Finally, in large quantities, an excess of nutrients (especially nitrogen and phosphorus) in groundwater can lead to eutrophication of water bodies (popularly known as “overturning” of water bodies) and thus cause severe environmental pollution.
For this reason, too, compost application in the fall is not recommended.
Can compost be used pure?
Compost can be applied “pure” to beds for fertilizing and incorporated, but should never be used “pure” to create a completely new bed.
Since compost is very rich in nutrients, i.e. contains a lot of phosphorus, potassium and sodium, similar to a conventional fertilizer, it should always be mixed with normal plant or potting soil or peat to create a new bed, so as not to over-fertilize the plants.
Like other fertilizers, however, compost can be easily spread and incorporated in its pure form as a nutrient supplier to existing beds.
How much compost to apply?
Across all different plant crops, you can apply an average of 2 liters of compost per square foot in the garden. This will ensure that plants are not over-fertilized but still receive adequate nutrients.
The exact amounts of compost that can be applied on average per square meter for the different plants are as follows:
- Vegetables: 2 liters of compost per square meter
- Woody plants: 1 liter of compost per square meter per year
- Perennials: 1-2 liters of compost per square meter per year
- Lawns: 2 liters of compost per square meter per year
The exact amount of compost depends on the crop, so that, for example, high-yielding vegetables, such as potatoes or cabbage, need more compost (3 liters per square meter) and vegetables with low nutrient requirements, such as lamb’s lettuce or asparagus, need less compost (only 1 liter of compost per square meter).
Spreading compost on lawns?
Compost can also be applied to lawns and thus used for lawn fertilization. The lawn should be fertilized similarly to all other plants during the growing season in spring and summer with about 2 liters of compost per square meter.
Compost should first be applied to lawns in spring, after scarifying. During the summer and fall, compost can be re-fertilized as desired, as long as a total amount of about 2 liters per square meter per year is not exceeded.
Where can you spread compost in the garden everywhere?
Compost can and should be applied to almost any area in the garden, i.e. vegetable or flower beds, lawns, under perennials or under fruit and ornamental trees.
Because compost is high in nutrients, it can be beneficial to almost all plants, providing them with phosphorus, potassium and sodium.
However, compost should not be applied to acid-loving bog plants – such as rhododendrons, blueberries or hydrangeas – because they are usually slightly alkaline.