Seeds, seedlings and repotting with EM: soaking seeds, compost and dilutions

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A good start often makes for a good harvest. Vigorous seedlings and sturdy, well-rooted young plants cope better with transplanting, drought and cold snaps. Many gardeners add effective microorganisms to their sowings: by soaking the seeds, moistening the compost or watering the young plants.

These steps are simple, but they call for weaker dilutions than in the vegetable garden, because young roots are fragile. Here are the doses, the right sequence, and what the few published trials actually show.

Why give your plants a good start

Before thinking about EM, let us recall what really makes sowing a success: plenty of light, a temperature suited to each species, light and clean compost, and regular watering without overdoing it. A seedling that lacks light grows leggy and weak, whatever you give it. Waterlogged compost rots the roots.

EM complement these good conditions. They are always used diluted in unchlorinated water: rainwater, or tap water left to stand for 24 hours. You can use EM-A Microferm Active Solution, ready to dilute, or an EM-A you make yourself from EM-1 Mother Solution, following our guide Activating EM-1: making your own EM-A step by step.

Soaking seeds

The best-documented soak is at 1 in 500, i.e. 2 ml of EM-A per litre of water (a small dosing syringe is very handy for measuring), for 30 minutes before sowing. This is the protocol used in the published trials on celery and tomato, and the dilution recommended by one distributor for sprouts and seedlings.

1. Prepare the solution in lukewarm, unchlorinated water.
2. Immerse the seeds in a small bowl or a cloth tea bag.
3. After 30 minutes, drain them on kitchen paper.
4. Sow straight away, without letting them dry out or waiting until the next day.

For very fine seeds (carrot, lettuce, strawberry), soaking is impractical: simply moisten the compost with the solution, as explained below.

What can you expect? The results are mixed. In trials on maize, sorghum and sunflower, treating seeds with EM did not change the germination rate under favourable conditions, but it gave better results under stress, particularly cold. Other laboratory tests on sunflower report better germination and longer roots. In other words: a possible small boost, especially when conditions are not ideal, but nothing that will make up for seed that is too old or a sowing that is too cold.

Preparing the compost

The day before sowing, moisten your compost with the same 1 in 500 solution. Mix well, so that it feels damp to the touch without being sodden: a tightly squeezed handful should not drip. Then fill your pots or trays.

A few rules for the growing medium:

• No kitchen bokashi or bokashi mulch in seed compost: too acidic and too coarse for young roots.
• A light, fine compost, renewed every season. If you make your own, our guide Making your own potting compost from your compost gives the right proportions, using well-matured, sieved compost.
• Clean containers, rinsed in hot water and dried.

Emy's tip

Always sow a few control pots, watered with plain water, alongside those receiving EM, and label them. It is the only way to see, in your own conditions, whether there is a difference.

Watering young seedlings

Once the seedlings have emerged, water them with EM once a week, and with plain water the rest of the time:

• From emergence to the first true leaves: 1 in 1,000, i.e. 1 ml per litre.
• From the first leaves to pricking out: 1 in 500, i.e. 2 ml per litre.

Ideally water from below, letting the pots soak for a few minutes in a saucer, then tip away the excess. Do not spray the seedlings' leaves, and never increase the dose: stronger does not mean more effective, and EM-A is acidic.

EM are no substitute for precautions against damping off, the collapse of seedlings at compost level: clean containers and compost, moderate watering, fresh air and sufficient light remain the only real defences.

Key points

The younger the plant, the more you dilute: 1 in 500 for seeds and compost, 1 in 1,000 for seedlings, and 1 in 100 only for well-established plants in the garden.

What the trials on young plants show

Two greenhouse trials carried out in Estonia on transplants are often cited. They are interesting, but must be read with their limitations in mind.

Leaf celery

The seeds were soaked for 30 minutes in a 1 in 500 EM solution, sown in peat treated in the same way, then watered weekly. Result: markedly sturdier plants (about a third shorter), with thicker stems and higher levels of nitrogen, phosphorus, potassium and calcium. But this was a single trial, over a single season, with no measurement of the harvest, and the three treatments were combined: we do not know which one made the difference.

Tomato

Here, it was diluted bokashi juice that was tested: seeds soaked at 1 in 500, then watered weekly at 1 in 1,000. Only stem diameter was significantly greater, by about 13%. The plants seemed slightly taller, but the difference was not significant, with a very small number of plants. Bokashi juice has its own rules of use, detailed in our guide Bokashi juice: dilution, uses and limitations.

Beyond these two trials, reviews count a majority of positive studies on vegetable growth, but this is a simple tally that does not weigh the quality of the trials. Field trials in temperate climates, for their part, show no clear effect on yields, as we explain in our guide What science says about effective microorganisms.

Did you know?

A smaller plant is not necessarily a failed plant. For transplanting, gardeners actually look for sturdy plants with thick stems, which establish better than tall, spindly ones.

Pricking out, planting and repotting

When pricking out

Water the plants with a 1 in 500 solution the day before, so that the root ball holds together, then again just after pricking out, so that the soil settles well around the roots.

When planting out in the garden

Water the planting hole and the root ball with the same solution. For larger plantings (shrubs, fruit trees, large container plants), you can mix a little bokashi mulch into the soil in the hole, at the rate given in our guide Using EM in the vegetable garden, mixing it in well so that no clumps are left in contact with the roots.

When repotting container plants

Moisten the new compost at 1 in 500, repot, then water with the same solution. For well-established plants, whether houseplants or balcony plants, the manufacturer of Microferm recommends regular watering at 1 in 100; in pots, where the roots have nowhere to escape, we advise starting more diluted, at 1 in 500, then moving to 1 in 100 if the plant is doing well. Always empty any water left standing in the saucer.

In summary

For sowing, soak the seeds for 30 minutes in a 1 in 500 EM solution, moisten the compost the day before with the same dilution, then water the young plants once a week at 1 in 1,000, then 1 in 500 until pricking out, always with unchlorinated water. When pricking out and repotting, stay at 1 in 500; the 1 in 100 dilution is reserved for well-established plants. Published trials show sturdier plants with thicker stems, but they are few and small in scale: EM complement light, warmth, good compost and careful watering, but never replace them.

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