Alex’s Compost Kitchen: Recipes for using Compost

Growing mediums

Specific potting mixes can be used to produce healthy seedlings and effectively grow plants in pots and containers. Garden soil has a complex balance of micro-organisms, air spaces and nutrient levels which can be lost in the artificial and restricted conditions of a container.

The ideal growing medium:

  • Moisture retentive
  • Well aerated
  • Contains an appropriate amount of nutrients to serve its purpose
  • Allows a vigorous root system to develop
  • Is uniform in consistency and predictable in behaviour
  • Is free from pathogens and pests

A growing medium will usually contain a carbon rich bulking material, a material to help improve drainage and possible a material to add nutrients depending on the end use.

Seed Sowing mixes: consist of fine-textured bulking material and possibly a material to improve drainage such as horticultural sand. Seed sowing mixes contain low nutrient levels as high nutrient levels can inhibit germination and growth of seedlings.

Cuttings growing mediums: Similar to seed sowing mixes. Often horticultural grit or perlite is used instead of horticultural sand to further increase drainage thereby reducing the risk of cuttings rotting instead of rooting.

Potting mixes: Used to pot up seedlings or cuttings once rooted. They need a similar texture and ingredients to seed sowing mixture but with the addition of a nutrient-rich material to sustain plant growth for an extended period of time.

Multipurpose growing mediums: It is possible to produce a mix similar to a potting mix but with lower levels of nutrients. This can then be used for both sowing, cuttings and potting on although as plants mature they will need additional nutrient feeding.

National Volunteer Masters Conference 2015. Written by Alexandra Heelis.

Recipes for seed sowing, potting and cuttings growing mediums
Use / Ingredients / Ratio (by volume) / Comments
Seed sowing mixes / Leafmould alone / Often sufficient on its own if sieved.
Leafmould : Loam / 1:1 / Gives good results with most seeds. Has enough nutrients until seedlings are transplanted. Too coarse for small seeds. Needs careful watering.
Comfrey leafmould: Sand / 4:1 / Will provide sufficient nutrients until potting on stage.
Potting mixes / Coir alone / Transplant seedlings promptly to avoid nutrient deficiencies.
Loam: Leafmould: Garden compost / 1 : 1 : 1 / A good basic mix, well-drained and fertile.
Leafmould: Vermicompost / 3 : 1 / Nutrient rich.
Loam : Manure : Leafmould / 3 : 1 : 1 / Very rich mix for heavy feeders such as pot-grown tomatoes and peppers.
Comfrey leafmould alone / Good for flowering and fruiting container-grown plants.
Garden Compost: Vermicompost / 1 : 1
Leafmould : Loam / 1 : 1 / Good for permanent plantings in pots. Use comfrey leafmould for a richer mix.
Cuttings growing mediums / Coir : Grit or Perlite / 1 : 1
Sieved leafmould : Coarse horticultural sand / 1 : 1 / Use well-rotted leafmould.

Sourced mainly from : Encyclopedia of Organic Gardening. Editor-in-Chief Pauline Pears. The Henry Doubleday Research Association.

National Volunteer Masters Conference 2015. Written by Alexandra Heelis.

Ingredients suitable for use in growing media

Vermicompost: The compost created from a wormery is called vermicompost and can be quite wet when first harvested. It may be easier to apply if you let it dry out a bit but do not let it become dust-dry. If you are not using it straight away it can be stored in a bin or bucket for a few months. Vermicompost is organic, far richer than normal garden compost, and has good water-holding capacity making it an excellent addition to hanging baskets. It can also be added to bought potting compost for an extra nutrient boost. Vermicompost can also be used as a soil amendment at sowing time by sprinkling it along marked out drills before sowing. This will give young roots an excellent nutrient boost. It can also be used as mulch around fruit trees, bushes and canes where the nutrients will give an additional boost to ripening fruit. Worm compost can be used for top dressing around plants in pots. It can also be used in a similar way to garden compost by applying in spring and summer to plants that need to put on vigorous growth.

Loam: There are three types of weathered rock particle that make up soil: sand, silt and clay. If these particles are in roughly equal proportions, the soil is called loam. If one type starts to predominate then it is called a sandy, silt or clay loam. When referring to loam in terms of a medium for a potting mix,this usually refers to a pasteurised, fine-textured top-soil (preferably with equal proportions of the particles discussed).

It is possible to make loam yourself. Turf, stacked and left to decompose will produce a crumbly, even-textured loam, ideal for use in potting mixes. The turf needs to be stacked upside down and covered with a light-excluding material such as black polythene or carpet for 6-12 months. If using loam in seed-sowing mixes it is best to pasteurise it to destroy harmful pathogens and weed seeds. This can be done by heating the loam in an oven (180⁰F for 30 mins) or microwave (time dependant on weight of soil and power of microwave). Sterilising loam is not recommended as it can kill beneficial micro-flora and can affect the way nutrients behave.

Leafmould: By composting only leaves in a separate compost heap, leafmould can be produced. It takes longer than normal garden compost and is best used after two years decomposition. It can provide a low-nutrient bulking agent that has good moisture retention and consistency. It makes an excellent seed sowing medium on its own and can be added to potting mixes to maintain an open structure.

Comfrey leafmould: Created using the same method as normal leafmould but only using comfrey leaves. This creates a nutrient-rich bulking agent high in potassium.

Garden Compost: Home-made compost can be used to provide nutrients as well as providing structure and acting as a bulking agent; it is best used in potting mixes. Garden compost may contain weeds and different batches will vary in quality and consistency.

Horticultural sand: This is sand that has been washed to remove salt, lime and other elements

Composted bark: Although unsuitable for small modules, composted bark can be used as a low-nutrient bulking agent. It is too free training on its own and so needs to be mixed with another finer material.

Coir: A natural fibre extracted from the husk of coconuts. It has good aeration and water holding capacity although the surface often dries out whilst underneath remains moist so it can be easy to overwater. Coir has a high potassium content and can be used as a bulking agent. Although coir has a pH of 5.8-6.5 it is unsuitable for ericaceous plants as they prefer a pH below 5.5.

Manure: Well-rotted ‘strawy’ farmyard manure provides bulk and nutrients. It is best used in rich mixes for long-term use such as tomatoes and peppers in pots.

Additional note on mulches

Mulching is where a material is spread over soil for any of a number of reasons including; improving soil structure, helping the soil retain moisture, insulating the soil from rapid temperature changes, suppressing weeds, attracting insects, covering bare soil, preventing nutrient leaching, supplying additional nutrients, and improving drainage. A number of the ingredients listed above are also suitable for using as a mulch including; garden compost, composted and non-composted bark and leafmould.

Liquid Feeds

Liquid feeds provide plants with nutrients in a readily available form. In organic gardening the aim is to feed the soil not the plant; however there can be times when a liquid feed is necessary in an organic garden. The primary purpose of liquid feeds is to boost container plants where the volume of compost is limited or to sustain young plants in modules where planting out is delayed.

Liquid feeds can be used in the garden but only as a short term solution where soil is poor, or soil conditions or root damage prevent a plant taking up sufficient nutrients. In the latter case, the feed is best used as a foliar spray to the leaves.

Organic liquid feeds should never be used as an alternative to good soil care and management.

Feeding plants in pots

The type of plant, its size in relation to the container it is growing in, how vigorously it is growing, how big you want it to grow and the quality of the growing medium will all affect how much and how often you need to apply liquid feed. Observation and past experience are very important and you need to be aware that you can over-do it; overfeeding encourages excess leafy growth, delaying the production of fruit or flowers whereas a tomato plant covered in fruit may need feeding three times a week.

Homemade liquid feeds (beware of the smell!)

Comfrey

Comfrey is a fast-growing hardy perennial growing up to 1m tall. Bocking 14 is a variety of comfrey developed by Lawrence Hills, founder of HDRA[1], now known as Garden Organic. Bocking 14 comfrey is high yielding and has a particularly high potash content. A sample analysis of comfrey concentrate made from Bocking 14 contains per litre, 79mg of nitrogen, 26.4mg of phosphorous and 205mg of potassium. Unlike other types of comfrey which spread rapidly, Bocking 14 does not set seed and does not have a creeping root.

Root cuttings or pot-grown cuttings of Bocking 14 should be planted in spring or summer. The leaves can be cut three or four times a year once the plant is established with the last cut in early autumn at the latest. Grass cuttings applied in spring and shredded prunings added in autumn, every year or two can be a very effective nitrogen-rich feeding regime.

Comfrey leaves are rich in plant foods and decay rapidly releasing the goodness they contain. Comfrey leaves can also be used as a mulch or compost activator. Comfrey based liquid feed should not be used on acid-loving plants as comfrey leaves tend to be slightly alkaline. Comfrey liquid is high in potash (see above) and has reasonable levels of nitrogen and phosphate.

Comfrey Concentrate

Pack comfrey leaves into a container without water. Cover with a lid. Ready in about 10 days. Use diluted 1:15

Comfrey liquid

Put 6kg of comfrey leaves and 90 litres of water in a container. Cover and leave for 4-6 weeks. Use undiluted.

Nettles

Nettles make a general liquid feed. It is fairly low on phosphate but also supplies magnesium, sulphur and iron. The highest levels of major nutrients are found in young nettles cut in spring.

Nettle liquid

Pack 5kg of nettles into a container and add 45 litres of water. Cover and leave for 2 weeks. Stir occasionally. Use undiluted.

Manure Liquid

Suspend a sack full of manure in a container of water. Allow to stand for 2 weeks. Use undiluted.

Worm wine (tea)

The liquid that collects in wormeries consists of runoff from the kitchen waste, moisture from rain and condensation and urine from the worms. This is a strong liquid fertiliser known as worm tea, but worm wine is way more fun. It’s fantastic stuff! Worm tea makes a valuable liquid feed when diluted at 10:1 with water. Once harvested, worm tea should be used as soon as possible. It may ferment if left for too long and could explode if left in a sealed container. It can be used for container crops and hungry plants such as tomatoes. When added to a compost heap it will also give it a boost and act as an activator. A liquid feed can also be made by putting some vermiculture compost into an (old) pair of stockings and suspend in a bucket of water for a week.

Bokashi liquid

The juice that is collected from a bokashi systems is an excellent, very rich plant feed that needs to be diluted with water at a ratio of 1 : 100.

National Volunteer Masters Conference 2015. Written by Alexandra Heelis.

[1] HDRA: the Henry Doubleday Research Foundation.