Organic Matter for the Greenhouse Border

Plant feeding

organic matter for the greenhouse border Plants in an organic garden obtain their food through the activities of soil organisms, which break down organic matter and release nutrients as plants need them. Ideally, the same should happen in a greenhouse, whether plants are growing in the border or in pots. Plants fed in this way are less likely to suffer nutrient overdoses or deficiencies, and generally will be much healthier.

Liquid feeds — even plant or manure-based ‘organic ones’ — bypass the soil life and are easily washed out and wasted. They are no substitute for good preparation of the border soil or potting compost, and they should be used only to give a boost to plants when absolutely necessary.

However you do it, giving greenhouse plants a balanced diet is not easy. There are two main problems:

  • Shortage of nutrients – The plants often need more nutrients than they would outside because they are growing more quickly. This need has to be satisfied from a small volume of compost in a pot or from an intensively planted bed.
  • An excess of nutrients – Too high a concentration of nutrients results in various disorders. This is rarely troublesome outside, where rain continually washes out soluble salts, but it is a common greenhouse problem.

Preparing greenhouse borders

It is preferable to grow crops in the greenhouse soil rather than in pots or growing bags. This gives them more root run and makes them easier to feed, provided that you give the soil the care and attention it needs.

Organic matter

This is essential, both to provide plant nutrients and to maintain the structure of the soil, which is at particular risk in a greenhouse from constant heavy watering in summer. Use compost, well-rotted manure, and other materials as appropriate to the crop, just as you would in the garden. They can be dug into the soil, or used as a mulch which will protect the soil surface and hold in moisture.

Organic Matter for the Greenhouse Border

Organic Matter

How to Use

Well-rotted strawy manure

Use this to provide nutrients and improve the soil. Fork into the soil each season before planting hungry crops, such as tomatoes and cucumbers, and permanent fruit. Also, use it for mulching them when extra nutrients are needed. The recommended amount is about 5kg per sq m.

Garden compost

Use this in a similar way to well-rotted manure. As it is more stable and the nutrients less available, it can be used in greater quantities. It is also suitable for flowers, shrubs, and climbers.

Fresh strawy manure

Traditionally, this is used for hot beds. If manure that is not well rotted is forked into the soil or used as a mulch, then there is a danger of:

  • Burning plant roots.
  • Ammonia gas building up in the greenhouse.
  • Excess nutrients building up in the soil.
  • Chemical residues from the straw affecting plant growth.

Leaf Mould

Dig this into very light or heavy soils to improve the structure without adding nutrients (and hence building up the salt level). It is also useful as a mulch, especially on winter crops.

Grass mowings

Use a thin layer as a mulch (but beware of a build-up of ammonia, and ventilate if necessary). It adds nutrients to the soil as it breaks down.


Use this as a mulch around mature cropping plants.

Proprietary products

Bagged manures, composts, and soil conditioners often contain a bulky substance, such as peat substitutes, plus a source of nutrients. Follow the directions on the bag.

28. November 2010 by Dave Pinkney
Categories: Garden Management, Greenhouse Gardening, Manures and Fertilisers | Tags: | Comments Off on Organic Matter for the Greenhouse Border


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