Green manure - plant selection, incorporation, pictures, tips and tricks

the essentials in brief

With green manure, a so-called catch crop is incorporated into the soil to improve the soil.
Legumes such as beans, peas or lupins are usually grown as catch crops, as these bind nitrogen and release it to the soil.
The roots are left around the soil to loosen the soil, the upper parts of the plant are lifted under.

“The fattest soil carries the most weeds.” (William Shakespeare, King Henry IV.)

What is green manure?

Green manure is a tried and tested method in natural gardening as well as in organic farming. It is carried out primarily to cover and improve the soil by incorporating fresh or wilted plants into the soil that have been sown especially for this purpose. The farmer calls these plants “catch crops” because they are not harvested but fed back into the natural nutrient cycle.

It is best to cut green manure plants shortly before or during their flowering so that no seeds develop and you subsequently have a colorful flower meadow instead of a vegetable patch. The roots of the green plants remain in the ground, are gradually decomposed and loosen the soil. The clippings, on the other hand, can be left until they are re-sown, where they serve as mulch material and compost.

Which plants are suitable for green manure?

Like all plants, green manure plants have their own special requirements in terms of location and soil. Incidentally, legumes, i.e. legumes such as vetches, beans, peas, lupins and also clover, are particularly important for this purpose, as their roots can bind nitrogen from the air and keep it in the soil. This is made possible by so-called nodule bacteria on the roots, the Rhizobium bacteria.

The following table clearly lists these and other important green manure plants, their location requirements and their effect on soil health.

Art	Latin name	sowing	Location and soil	Effect on the ground
Broad bean	Vicia faba	February to July	good for dry soils	Deep roots for loose soil, good nitrogen collector
Alexandrine clover	Trifolium alexandrinum	April to October	sunny, moist soil	Nitrogen collector, suppresses weeds
Bee friend	Phacelia	April to October	very good for nutrient-poor soils	Bee pasture, acts against nematodes
Blue flax	Linum usitatissimum	April to June	also for partially shaded locations	Deep roots for loosening the soil
Blue lupine, fertilizer lupine	Lupinus angustifolius	April to October	also for partially shaded locations	valuable nitrogen collector, deep-rooting for loose soil
Buckwheat	Fagopyrum esculentum	May to August	for low-lime sand and heather soils, including bog soils	fruit-neutral (knotweed), bee pasture
Hornschotenklee (common horn clover)	Lotus corniculatus	March to August	very good for poor, dry and lime-rich soils	Deep roots for loose soil, good nitrogen collector, valuable bee pasture
Oil radish	Raphanus sativus var. Oleiformis	April to September	very good for compacted soils	Deep roots for loose soil, not before or after cabbage plants
Pannonian vetch	Vicia pannonica	August to October	for sunny locations	good nitrogen collector, for winter cultivation
Red clover	Trifolium pratense	March to September	for deep, fresh soil	Deep roots for loose soil, fast-growing, nitrogen-forming
Marigold	Tagetes	May to June	very good for partially shaded locations and moist soils	Deep roots for loose soil, bee pasture, combats nematodes
White mustard (also yellow mustard)	Sinapis alba	March to September	very good for compacted soils	Deep roots for loose soil, not before or after cabbage plants
White clover	Trifolium repens	February to October	for sunny locations	good nitrogen forming
Winter rape	Brassica napus	May to September	for nutrient-rich soils	good for loosening the soil, for overwintering, not before or after cabbage plants

Digression

Spinach as a green manure

The hardy spinach (bot. Spinacia oleracea) is also suitable for green manure, but only to a limited extent. The vegetables are suitable as a preculture and should be sown early in the year - between March and May. The strong tap roots of the fast-growing plant loosen the soil well and prepare it for suitable secondary crops. Spinach contains saponins, which promote the uptake of nutrients by other plants, improve soil life and thus indirectly water storage, shade the soil and prevent it from drying out. That is why spinach is very suitable for a mixed culture with almost all other vegetables.

However, leafy vegetables also have a disadvantage: They accumulate nitrate in the soil and should therefore not be cultivated together with high-consumption foods such as peppers, cabbage plants and celery. Other vegetables from the same plant family - beetroot, Guter Heinrich, Swiss chard, garden cress and rocket - are not suitable for mixed cultivation and crop rotation.

If the soil is mulched with spinach, this attracts earthworms - these in turn are indispensable for the production of valuable, nutrient-rich humus.

Sowing and timing

The green manure is sown between March and October, depending on the selected plant species. It is best to proceed as follows:

First remove any growing weeds with a rake.
Work the soil thoroughly with the hoe, loosening the upper layers of soil.
Crush the clods of earth with a rake.
Sow the seeds broadly on the prepared area.
Alternatively, if available, you can also use a spreader.
Then work the seeds flat into the ground with a wide hay rake.
Finally, go over the seed area with a lawn roller, if available.
Irrigate the area when it is dry.

Most seeds will germinate in about six to 14 days, depending on the type of plant.

Pre-sowing

Green manure applied in early spring between February and March is called pre-sowing. It primarily serves to nourish and activate the microorganisms living in the soil after winter. For this form of green manure, choose plant species that are tolerant of frost, such as spinach (bot. Spinacia oleracea), lamb's lettuce (bot. Valerianella locusta), Phacelia (bot. Phacelia tanacetifolia) or yellow mustard (bot. Sinapis alba).

These plants remain on the surface until you plant or sow the actual crops. The green manure can remain between the rows of vegetables in the bed as so-called undersown and is only cut occasionally if it grows too strongly.

Under- and inter-sowing

Under- and intermediate seeds should cover the soil between different perennial vegetable crops such as corn, tomatoes, cabbage or berries. Here you apply the green manure plants as soon as the crops have grown. Annuals such as nasturtium (bot. Tropaeolum), marigold (bot. Tagetes erecta), marigold (bot. Calendula officinalis) or purslane (bot. Portulaca oleracea) are particularly suitable for this purpose. A pleasant side effect of these plants is that you can also use them in the kitchen or in the medicine cabinet.

Overseeding

After the harvest in late summer, the vegetable beds can be covered with overseeding. You can sow these two to three weeks before the harvest - for example as undersowing between the rows - so that the fallow phase is no longer necessary. Most of the plants used for this are not hardy and die with the first frost. The effect is intentional, because under the frozen plant matter, the soil remains protected and loose. Instead of frost-sensitive species such as yellow mustard, phacelia or sunflower, you can also use hardy leafy vegetables such as spinach and lamb's lettuce. However, this variant is only recommended if the beds are to be planted late in the following year.

When and how do you have to incorporate the green manure?

Apart from the wintering species, the green manure plants remain on the beds for about five to ten weeks and are then mowed. However, do not clear away the plant residues, but leave them in place as mulch (€ 99.99 on Amazon *). They rot there and go into the ground as humus. Green manure plants that remain low, such as garden cress and lamb's lettuce, are not mowed, but worked directly into the soil from a height of around five centimeters.

Mowing before the seeds ripen

In addition, make sure to mow the plants before the seeds are ripe, otherwise you will have a problem with masses of wild germinating plants in the following year. Green manure plants that are not hardy, on the other hand, usually freeze before the seeds ripen and can therefore remain. Here you do not mow the leftovers until spring and work them flat into the ground. The bed can be reordered after another three to four weeks.

Work green manure plants into the soil

Mowing is done with a scythe, with a brush cutter (94.07 € at Amazon *) or with a powerful lawnmower. The latter is especially the device of choice when it comes to a mulching mower. The green manure plants, which are equally well chopped up, rot faster. Do not work the mowed plants into the ground straight away, but let them dry for a few days. this is especially true for species with a lot of leaf mass, as they can otherwise rot in the ground. Green manure plants with woody stems (for example sunflowers), on the other hand, are not incorporated at all, but are well chopped and composted on the compost. Here the decomposition process is simply too lengthy to work the remains into the soil straight away.

You have to pay attention to this with green manure

When choosing the plants, there are some tips to consider with regard to crop rotation or a mixed crop. For example, representatives of the same plant family must never be grown one after the other on one area, as otherwise certain pathogens accumulate in the soil and threaten the subsequent harvest. Typical examples of this are nematodes and clubheads. Furthermore - especially with legumes - excretions from the roots lead to self-intolerance.

Note crop rotation

For this reason, you should take three to four years of cultivation breaks before you cultivate a representative of a particular plant family on the area again. Specifically, this means: If you want to grow cruciferous vegetables such as cabbage, radishes or radishes in your vegetable patch, you must not sow rapeseed, oil radish or mustard as green manure. If, on the other hand, peas and beans are planned, lupins, vetches or clover should not be used for green manure.

Phacelia for the vegetable garden

Phacelia, on the other hand, is ideal for the garden, as it is not closely related to any vegetable and therefore mutually exclusive. The same applies to buckwheat, a knotweed plant that should simply not be associated with rhubarb. The marigold, also known as marigold, helps against root-damaging nematodes.

How does green manure work?

Green manure is not so much an actual fertilization, but rather a measure to improve the soil. Harvested vegetable beds, but also fruit beds and other garden areas benefit from green manuring in several ways. Depending on the choice of plants and the desired use, this can be sown as the main crop, catch crop or undersown or, however, rarely, planted.

Green manure in the vegetable patch

Green manuring is particularly useful before or after the cultivation of heavily consuming vegetable plants such as tomatoes, peppers, potatoes, artichokes, melons, etc., as these plants leach out the soil despite additional fertilization. Soil improvement measures as well as sensible crop rotation and mixed culture allow the soil to recover more quickly and the harvest yields to increase.

View this post on Instagram

A harvested bed was replanted 😊 the harvested peas were chopped very small with the spade, they serve as green manure. On top of it a thin layer of compost, enriched with primary rock flour and horn shavings. 16 white beets were now placed in the outer circle, 8 kohlrabi lanro in the inner circle, 4 x colorful chard in the middle circle and 1 x yellow chard in the middle 😊 I'm curious how it will look in a few weeks 😊 #neuesbeet # green manure # weisserüben #kohlrabi #lanro #buntermangold #mangold #bed processing # foundation # primeval rock flour # horn shavings # fertilizer # fertilization # organic vegetables # vegetable garden # vegetable cultivation # vegetable patch # vegetables # organic #stefanshobbygarten

A post shared by Stefans-Hobby-Garten (@stefans_hobby_garten) on Jul 8, 2019 at 10:57 am PDT

Green manure for soil improvement

Unfavorable soil conditions, such as the soil compacted by heavy construction machinery in the new building areas, can be improved by green manuring, as the plants loosen the soil with their roots and thus protect it from clogging. Phacelia (bee pasture), winter rape and yellow lupine are particularly good for loosening the soil. At the same time, these plants increase the valuable humus content due to their rotting plant mass.

Green manure in the orchard

In the orchard or the orchard meadow, flowering green manure plants - sown as undersown - attract many insects, which in turn pollinate the apple and pear trees. This also contributes to a rich fruit harvest, especially since the trees benefit greatly from additional nutrients.

Green manure for the garden has these advantages

Aside from those already mentioned, green manure has many positive effects on the garden. The dense carpet of plants not only suppresses the growth of unwanted weeds, but also prevents soil erosion and the washing out of nutrients from the fallow soil. This is no longer unprotected due to the targeted planting.

Enrichment of the soil with nitrogen

The green manure plants not only receive the nutrients already contained in the soil, but also enrich them with fresh nitrogen. Legumes filter the nitrogen from the air with the nodule bacteria in their roots and later, after having been incorporated into the soil and decomposed, to the following plants. Thus, vetches, beans, peas and lupins act practically as natural long-term fertilizers.

Loosening of compacted soils

Green manure plants with deep roots - for example, alfalfa and oil radish - are also able to loosen highly compacted soils and thus make them usable in the first place. This property is particularly important in new development areas, where the soil is often very compact due to the construction activity with heavy machinery.

Enrichment with humus material

Still other species - for example winter vetch or phacelia - are perfect for enriching depleted and / or sandy soils with humus and thus making them fertile again. These plant species develop a lot of leaf and flower mass, which composts in the soil and thus activates the soil organisms.

The advantages of green manure at a glance:

rapid greening of fallow areas
Protection of the soil from the weather and thus from erosion
deep loosening and aeration of the soil
Improvement of the soil structure
Enrichment of the garden soil with nutrients
Activation of the soil organisms that are important for humus formation
Absorption of nutrients (especially nitrogen) from the air
Utilization of nutrients from deeper soil layers
Suppression of weed growth
Clippings result in valuable mulch material
Insect pasture by means of flowering green manure plants
some green manure plants fight nematodes (roundworms) and fungal diseases in the soil

The following video shows very clearly how the soil can be improved with green manure and what you specifically need to consider:

frequently asked Questions

Can you also sow summer flowers and use them as green manure?

Of course, you can also use summer flowers for green manuring, especially since you are not only doing something good for your garden: The flowering plants attract numerous insects and serve as valuable pasture for bees, bumblebees, butterflies and other animals. This nutritional function is all the more important the later it is in the year, as many insects no longer find enough food from the summer months. Borage, sweet peas, marigolds, marigolds and sunflowers are particularly suitable for this purpose.

However, blooming green manure also has a disadvantage: As soon as the seeds ripen, you will have colorful flowers in the garden over and over again in the years to come - usually exactly where you don't want them. For this reason, you must mow the plants in good time before the seeds ripen. Also note the crop rotation, which is particularly important in the vegetable garden: Under no circumstances should plants from the same plant family be planted in the same place one after the other. This promotes diseases! For example, marigolds and sunflowers may not be grown before or after salads.

Which green manure plants make the soil particularly loose?

The cultivation of green manure plants - depending on the selected plant species - has different effects on the garden soil. Firm and compacted soils, which are unfortunately typical in new building areas due to construction machinery, cannot only be loosened with mechanical work. To loosen the soil, also plant deep-rooted plants such as bitter lupins (or generally lupins), oil radish or sunflowers - their roots also reach the lower soil layers and thus ensure better ventilation and permeability.

Which green manure plants are particularly suitable for the vegetable garden?

Choosing the right green manure for the vegetable garden is not that easy, after all, for reasons of plant health, no plants from the same family should be grown one after the other. However, this means that many of the otherwise recommended green manure plants are omitted, because cruciferous vegetables such as mustard, cress or rapeseed do not get along with cabbage plants, radishes or radishes - the unpleasant result would be cabbage hernia. However, there are also suitable green manure plants that are true all-rounders and can actually always be grown: Phacelia is one of them, but also winter cereals such as winter barley or winter rye.

Why are winter grains problematic in the vegetable garden?

Winter cereals as green manure plants have many advantages: The seeds are cheap and as cereals the different types are not related to any vegetables and can therefore be sown without hesitation. However, winter rye and co. Have a disadvantage: They develop very dense roots, which can only be removed or incorporated in spring with a lot of strength and effort.

Tips

If you want to use legumes such as clover or lupine for green manuring, fertilize the soil with some primary rock flour or algae lime before sowing. The natural material promotes the activity of the nodule bacteria in the roots of the plants.

Grow and incorporate green manure

the essentials in brief

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What is green manure?