Seeds, germination, and seedlings

Germination test

A germination test is a good way to determine the approximate percentage of viable seeds in a given batch of seeds. It is especially useful for seeds saved by amateur gardeners or for old batches of seeds.

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To do a germination test, simply take a representative sample of about 10-20 seeds of a seed batch. To obtain a representative sample, simply pick the seeds at random: picking only the best looking or biggest seeds from the batch would not be a good way to test the whole batch. Put the seeds between two layers of wet paper towel or wet biodegradable coffee filter, place in a sealable plastic bag, and let sit in a dark and warm place. Keep the paper material moist at all times, without adding too much water in the bag. Every few days, check the seeds to see if any sprouted yet, and compare the time of germination to what’s written on the seed packet. Seeds that do not sprout at all are not viable, and seeds that sprout are viable. The germination rate is the percentage of viable seeds in the sample (i.e. seeds that sprouted).

Soaking seeds

Soaking seeds before planting them helps get a faster and more uniform germination. Seeds need water to soften up and get activated to initiate growth. Yet, when sowed dry in the soil, they get less water at a time and at a less uniform rate in space and time (if the soil dries between watering sessions, or if an unequal soil structure or planting depth doesn’t allow as much water to reach all seeds equally, for example). When soaked, seeds get to absorb all the water they need before being planted in the soil.

To prevent fungal and microbial growth, seeds can be rinsed with a 1 part bleach to 10 part water solution before soaking.

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To soak seeds, simply put them in clean lukewarm water. It is preferable not to allow seeds to germinate before planting, as it is easier to contaminate the sprouts once they have germinated. For this reason, never let seeds to soak for more than 24 hours, unless they don’t look ready. A well-soaked seed will have swollen and lightened in color, and its hull will have softened. Beet seeds have a very hard shell and it is better to soak them for a full 24-hour, if not more. Likewise, large bean seeds may need more than 24 hours of soaking.

Thoroughly submerge the seeds and place them in a warm, dark spot. Small seeds tend to stick to fingers when wet, so they can be put in a water bottle with their soaking water and squeezed out to plant. They can also be put to soak between moist layers of toilet paper or biodegradable coffee filters placed in a hermetic bag, and then planted along with the paper material. Other people also prefer to mix the wet seeds with wet sand and to sow the whole mix. Bigger seeds can be planted by hand, and are also the ones that benefit the most from soaking (since they need more water).

Seeds should be planted right away after being soaked. Once the soaking is done, seeds should not be left to dry or to soak longer before planting.

Finally, soaking seeds only allows for faster and better germination under normal conditions. Soil temperature, sowing depth, regular watering and well-prepared seed bed (amended with compost, loose soil, etc.) should thus not be overlooked when sowing.

Preparing the seedbed

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Seeds will need a rich, well-aerated, loose, and moist but not wet soil for planting. If the soil is too hard or too compact, dig a large hole where lighter soil will be mixed with the garden soil. This will allow the seeds to germinate without too much difficulty while encouraging strong root growth (if the roots are too weak, the harder soil will be impossible to penetrate and will act as a container for the plant).

A good potting mix should include the following : water-retaining fibres such as peat moss or coconut fibres, solid organic fertilizer, perlite, and compost. Using 5 gallons buckets, the recipe is :

-3 buckets peat moss

-2 cups organic fertilizer

-1 bucket perlite

-3 buckets compost

Wet the mix before using.

Sowing seeds

Whether they are sowed directly in the garden or to be grown as seedlings, seeds are planted the same way. It is also useful to keep a propagation record detailing the sowing date, the germination date and the rate of success, as well as the date when seedlings are ready for transplanting. This way, it is easier to notice what went right and what went wrong, and adjust accordingly the following year.

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After soaking the seeds, place them in the soil at the recommended depth. As a rule of thumb, seeds should be planted at a depth of twice their diameter (no more than 3-4 times the diameter), but it is better to look on the seed packet or the internet for specific instructions. Very small seeds can simply be sprinkled on the soil surface. If planted too deeply, the seeds may germinate but die before reaching the surface. If planted too shallowly, wind or rain may blow or wash the seeds away before they sprout. When planting during the summer, sow the seeds slightly deeper, as the soil dries quicker.

Gently tamp down the soil over the seeds to allow good contact between the soil and the seeds. Water to moisten the soil. It is better to plant seeds with half the recommended spacing and then thin once they germinate, in order not to leave empty spaces in the garden due to failed germination. Similarly, preparing more seedlings than necessary is useful in case some seeds do not germinate (seeds rarely have a 100% germination rate).

Make sure that you don’t water the seeds too much and that there is good aeration (in the aerial parts of the plants and in the soil), otherwise some fungal diseases might develop and kill the plant not long after it germinates. When watering, use a gentle spray to avoid disturbing the soil and seeds. A light mulch over newly planted seeds can help conserve moisture.

Sowing techniques

Rows: using a hoe, dig a straight furrow, plant.

Wide rows: seeds can be scattered over the surface or planted in blocks (i.e. the same crop will be planted in a same block instead of a row, so that a bed will be a succession of blocks instead of row of crops)

Hills: for cucurbits and corn. Not mounds; hills are groupings of seeds, not actual hills (which result in dry soil). Sow 4-5 seeds in 6-8 inches circles, using recommended spacing. Thin to 3 plants later.

Square-foot: 1-by-1 ft squares, single crop at a time, the amount of plants per square depends on the recommended spacing (minimum 1 large plant, like a tomato plant, except for squash which use at least 2 squares each)

Taking care of and hardening the seedlings

Growing conditions for seedlings include proper soil temperature, exposure to sunlight, fertilizing (if necessary), soil mix, and watering. Normally, seedlings will grow best in a constant environment, with 12-16 hours of light per day, constant temperatures, no wind, good aeration and a constantly moist but not wet soil. Heating may be necessary, but more watering will be needed for warmer temperatures. Give the seedlings a quarter-turn each day for even sunlight exposure.

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Seedlings need to be hardened before being transplanted in the harsh outdoors. As they’ve been growing in a controlled environment, with no wind, warm and constant temperatures, and with a constant supply of water, indoor-grown seedlings are more fragile than seedlings growing from garden-sowed seeds. It is thus necessary to make them hardier to the natural elements before they face the sad, sad reality of this world. Do not transplant seedlings if they show signs of stress or wilting; allow them to recover first, by putting them back into an artificial environment if needed.

First, to thicken seedlings stems, one can simply brush the seedlings with their hand a few times a day as they are growing indoors. This can be done as often as possible, by making sure not to break, weaken or damage the seedlings.

Then, one to two weeks before transplanting them, seedlings need to be gradually accustomed to direct sunlight, desiccation, wind, temperature changes, etc. The first step is to take the seedlings outdoors for a few hours in a shady, protected area. Over the next few days, seedlings should be exposed gradually to direct sunlight and wind for longer periods. They should also be allowed to go a little dry between the watering during the hardening process.

Transplanting seedlings

When transplanting, one needs to be careful not to break or damage the aerial parts (stem, leaves) of the seedlings, but also, more importantly, not to disturb roots to allow a quick recovery after transplantation. Water seedlings before transplanting.

Try to transplant in the late afternoon or on a cloudy day, so as to avoid stressing seedlings with excessive heat. If this is not possible, cover the seedlings with a thin layer of straw to shade them a bit.

If using biodegradable pots (e.g. peat pots), the pots can be transplanted with the seedlings, but the pots need to be completely buried, as they will otherwise act as a wick that will draw moisture from the soil on windy and/or dry days.

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To remove a seedling from a plastic pot without disturbing the roots, place a hand over the pot in order to receive the soil block and to secure the seedling without breaking it. Then, squeeze and/or tap gently the bottom of the plastic pot too loosen the soil, and finally flip the pot upside-down to let the seedling fall gently in your hand. If the root ball is tangled up, gently untangle the external roots before transplanting. Seedlings can also be gently pulled by the leaves to get them out of their pot.

Make sure that the transplant hole contains loose soil with compost (but not too much). If the garden soil is very compact or very different from the planting soil used for the seedling, dig a large hole and mix garden soil with the planting mix. This will act as a transitioning zone so the seedling roots do not encounter a physical or chemical wall as they grow.

Water the hole before adding the seedling. The seedling should be transplanted so its stem is slightly under soil level (basically you want the surface of the root ball to be level with the garden soil surface). Some seedlings can be buried up to their first true leaves, like tomatoes that will grow additional roots from buried stems. Surround and cover the seedling roots with soil, and tamp gently to ensure good contact between the root ball and the soil. Water a bit more if necessary.

Early transplants may need a cover to avoid frost. Make sure, though, that it is well aerated, otherwise the seedlings may suffer from heat shock. All seedlings should be mulched lightly after transplantation to conserve moisture and reduce transplant shock.

Do not allow seedlings to flower. Remove the flowers, as blooming needs a lot of energy that would be better invested in root or stem growth at this stage.

Planning is important

Before planting time (March) comes, a planting calendar must have been done. Indeed, not all plants are sowed/transplanted indoors/outdoors at the same time, depending on the soil temperature. An approximate calendar can be made using the average last frost date (LFD) of the locality.

Soil temperature

A more accurate method to sow/transplant at the right time is using soil temperature. Soil temperature can be measured with any glass bulb thermometer. Make sure to make multiple readings during the day (at least one in the morning and one in the late afternoon) at the recommended sowing depth. Make a pilot hole with a screwdriver for the thermometer to avoid breaking it. When measuring the temperature, sunlight can skew the measurement, so make sure to shade the thermometer and to give it some time to get an accurate measurement before reading it.

Frost hardy plants -Seed at 4°C (soil) -Grow in 10-24°C (air), hotter than this and they risk bolting -When mature, can survive frost as low as -7°C (air) -In general, can be planted 2 to 4 weeks before the LFD -Seedlings must be protected from temperatures lower than 4°C (air) -Warmer temperatures tend to make them taste bitter	Asparagus Brussel Sprouts Cabbage Collard Garlic Horseradish Kale Kohlrabi Leeks Mustard Onions Parsnips Peas Radicchio Radish Rhubarb Rutabaga Spinach Swiss chard Turnip
Semi frost hardy plants -Seed at 10°C (soil) -Can survive as low as -1°C (air) -Can be planted 1 to 2 weeks before the LFD	Arugula Beets Broccoli Carrots Cauliflower Celeric Celery Chinese cabbage Endive Jerusalem artichoke Lettuce Potato
Frost-tender plants -Can’t survive frost -Heavily damaged by low temperatures -Seed at 16°C (soil) when all dangers of frost have passed -Can be planted 1 to 2 weeks after the LFD	Artichoke Beans Okra Peppers Pumpkin Southern Peas, Spinach NZ Squash Winter Sweet Corn Tomatoes
Very frost tender plants -Last group to be planted -Seeds will rot in wet, cold soil -Plants are intolerant to cold spring winds -Daytime temperatures (air) of 13°C may retard growth -Seed at 21°C (soil) -Can be planted at least 2-3 weeks after LFD	Cucumber Eggplant Melons Squash Summer Sweet Potatoes