Starting Your Own Seedlings

Starting Your Own Seedlings

Starting your own seedlings requires some calculations to determine how many plants are needed based on the room available.

Usually, a seed packet has approximately twenty-five to two hundred and fifty seeds or more.  How expensive the seed is, depends on the variety and whether it is a hybrid, a new variety or a heavy seeder. If you get two hundred and fifty seeds in the packet, do you really need or want two hundred and fifty seeds?

Figuring out how many seedlings to start takes a simple calculation. Say you want to have twelve plants. Look at the package of seeds that states the percent (%) of germination. Not all companies state it on the seed packet but many do. The seed packet does have to state the year the seed was packed for, the amount of seeds, and the days to maturity, as well as providing directions on planting in terms of depth, spacing, etc. The minimum required germination rates can be from 55%, like in carrots, to 80% as in lettuce. Not too many packets will have the 100% germination rate. If you know the germination rate, divide the number of plants (twelve) by the percent of germination. This is important because, if the germination rate is low, then you could end up short on plants.

Testing Seeds

If the seed is older, saved from prior years, or if the package does not state the germination rate, you can test it yourself. Take ten seeds and place them in a damp paper towel – not dripping wet but moist enough so that the seed feels moisture. Fold the paper towel in half or place a second moist towel on top. Place inside a plastic bag or wrap in plastic and place it at room temperature. The seed package should state days to germination. Example: If it states seven days to germination, check the seeds on the seventh day and count the number of seeds that actually germinated. If you got six to germinate, then you have 60% germination. I recommend that, once the germination is below 50%, it is best to get rid of the seed and start with fresh seeds.

If you don’t use all the seeds the year the seed was packed for, it will lose germination as time passes. To retain the longest possible germination, keep them in a dry cool place, like a plastic container or a bag in the refrigerator.

How deep you should seed them is different for every single type of vegetable and seed type.  The rule of thumb is to seed them two times the diameter of the seed.  Any deeper, and they will likely not germinate or they may come up very late after some of the soil on top has washed away.

Keeping records

Whether direct seeding or growing seedlings, label the area. Seedlings sometimes look very similar, and we will forget. Also, the variety may slip the mind. If something does real well and you like it, you want to grow it again but if you can’t remember or find the variety that you grew, you won’t be able to. Write down a plan for the seed and the variety, especially when you do the growing of transplants.

Preparation of soil mix

The Potting Mix

Potting mix should be at least 30% organic matter, if not, then add some so that enough nutrients are in the mixture to get the plant to a good start. You can add compost or composted manure. Do not add raw manure or compost that is not fully finished, as it will burn the seedlings. If the mixture is too weak nutritionally, then the plants will be more susceptible to disease. When filling the containers to the top, lightly press down but do not overly compact them.


These can be anything that is big enough to hold a plant for a good four to eight weeks. If you use something that will fall apart with ease within that time, then use something else. For example, maybe try a paper pot. Just make sure it is thick enough to withstand the regular watering and will not break down before it’s time to transplant it.

Some are made of peat and these you can just take the whole container and place in the ground once they are ready to transplant. Again, see that they are not too thin. Fill them to the top with the media. The media will settle some and, when you transplant them, the ridge that is at the top edge must be cut back first, as it will draw the moisture from the soil and can easily prevent the pot from rotting once in the ground. This would limit the roots from expanding and developing into a good root system, which will result in a poor plant as well as poor production.

You can use any type of plastic containers, like ones from old yogurt or tofu. Just make drainage holes at the bottom. A good three to four holes will suffice for water to drain without allowing the soil to wash away.

You can also purchase plastic flats and reuse them every year. Just wash and sterilize them well with a little vinegar or bleach water. They do sell containers with a plastic lid that you can place on top once you place the seeds in the mix.  You can also use plastic to cover them. Remove the cover once the seedlings emerge.

Temperature Requirements

You need warm conditions above 60° for germination to take place. The rule is that the temperature should be at least five degrees higher than what is required for the actual plant to grow. This will vary if we are dealing with cool weather crops versus warm weather crops. But, overall, a safe temperature will be around sixty degrees. If you use your basement with some lighting, it should be good enough.  An unheated garage may be too cold and the seeds would not germinate.

Light Requirements

A window will work provided it is a southern exposure getting at least five to six hours of sun.  You will just need to rotate them and not have a tray that is too big; otherwise the middle plants will suffer. Keep in mind that if they are too close to the window, then the cold coming through from the glass will affect the overall temperature. The best situation is to have a full spectrum light over a table. Raise the lights as the seedling get taller so they don’t get burned. If the plants begin to look leggy, then they may not be receiving enough light. As the plants get taller and bigger they will compete for space as the leaves overlap each other. Enough light has to be provided in order for them to properly grow, but not so close as to burn them.

Watering and Fertilization

This is the hardest part. If you overwater, you are likely to kill them, as diseases like botrytis will proliferate at high moisture levels. The moisture level has to be such that it’s moist to the touch but not all the time. Water in the morning and allow them to dry as the day goes by. If they are by a window, this can be tricky, as the plants in the back may get less sun than those in front.  Also, you would water less on cloudy days. Too much water will also cause roots to rot. Check to make sure that the water comes out of the bottom.  If the drainage is not good, then the water will settle at the bottom and rot out the roots.

How to water is also important, as you don’t want to use a strong flow, which can easily bring the seed to the surface, wash away the soil, and give more water than is desirable. Therefore, water lightly but test the soil. If it feels moist to the touch on the surface, then skip the day and let the surface dry out.

If the leaves begin to look slightly yellow, then add some fish emulsion as fertilizer following the instructions on the bottle.

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The plant should be well of its way in its developmental stages. It should have various sets of true leaves versus the initial leaves it puts out (these are not true leaves – they are like baby teeth that will fall off). The root system should be well developed but not so much that it is getting out of the container.

Initially, place them in the shade outside by a tree and change their location every day. Little by little, by moving them closer to where they will end up, they will adapt to the type of sun they will receive once outside. At night cover them with a cloth or special fabric to prevent them from extreme weather fluctuations that they are not used to. Do this for the initial four evenings.  Do not water every day but rather begin to skip a day and even two days. If it’s windy, leave the fabric on the seedling, unless you have been practicing touching motion and slowly remove the fabric as you get closer to the final planting location. Once you start hardening them off, do not add any nutrients or fertilization.

Read about  Growing cabbage that needs transplants.

Make Your Transplants Stronger

Play music that is soft and pleasing. Most large nurseries know that plants respond to touch and sounds. Many have classical music playing inside the greenhouses.  Also, take the time to gently touch the seedlings as you walk along the side of the trays.  Gently making them bend over but not so strong as to break them. This gentle touch in a different direction each day will make the stems thicker and create a more resistant plant against winds and probably diseases. The movement mimics wind and, consequently, the plant stem will thicken up to counteract this “wind”.  If you do this, you will not have to worry if it’s windy outside.

Root Crops do Not Need Transplants 

Root crops really don’t do well when transplanted. If you break off the tap root that these plants give, they are unlike to develop another afterwards. It’s best to direct seed them (carrots, beets, radishes). Also, corn, peas, beans and the like need to be direct seeded.

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