From Seed to Garden

by Craig LeHoullier

A frequent comment that I get when people find out about my hobby of growing many varieties of heirloom tomatoes is are there any special tricks to use? My response is often something along the lines of saying that tomatoes are nearly like weeds, in that they are easy to grow, often come up where they are not expected, and are very forgiving of growing conditions. They are also very vigorous plants that grow until killed by frost or disease. There are, though, some things that are necessary for success.

I am not a gardener who goes in for the latest expensive gimmick described in the avalanche of gardening supply magazines and flyers that are delivered amongst all of the seed catalogs. People have been growing things for as long as man has been on the earth, and prior to the availability of expensive containers, sprinklers, or fertilizers. Gardening begins with seeds; after that, you need something to plant the seeds in, a container to hold that something in, water, heat and light. Let’s take these ingredients one at a time:

1. Seeds: Seeds are what make preservation of old varieties possible. Organizations such as the Seed Saver’s Exchange were founded upon maintenance and trading of seeds that may have immigrated from foreign lands, been passed down from generation to generation, or are otherwise not widely grown. Tomato seeds are viable for a long time when they are saved properly and kept dry. Last year I had very good success germinating varieties that I saved in 1987 (that is 7 years!), which were kept in glass vials and stored in my garage, which gets cold in the winter and very hot in the summer. If I were to freeze the seed, it would keep even longer. You can never be sure that the seed that you receive from another seed saver is viable, though. Another potential problem is the genetic purity of the seed you receive, but that is another story.

2. Containers: There is no need to be fancy or expensive in choosing what to start your tomato seedlings in. I like to use the thin black plastic 4-or 6-paks that are available in garden centers in late winter. I do not like to recycle them from year to year, as I do not want to risk my seedlings acquiring diseases from previously used containers. I mentally divide the 4-paks down the center, and plant 3 seeds of each tomato variety in each half, labeling the outside of the paks. That way, I will have a maximum of 8 varieties, 24 plants total, in each 4-pak. What is most important about the container, in my opinion, is that there are holes in the bottom to allow drainage, and that the cube of growing medium with its host plant can be easily removed without having to dig out the plant and risk damage to the roots. For growing lots of varieties of tomatoes, small is better also. Tomato seedlings take up little room, and they will not be in the original germinating container for very long, anyway.

3. Growing medium: DO NOT USE POTTING SOIL OR GARDEN SOIL! This cannot be stressed enough! I suspect that many a seed has rotted and failed to germinate in these way-too-heavy substances that can also crust when dry and carry diseases. The best thing is to buy large bags of a soilless mix, like Peter’s, Pro-mix, or Jiffy Mix. It is light and fluffy, absorbs water quickly, and does not crust over when dry. It also allows good root development, and plants are easily removed from the medium without a lot of root damage. Let’s say it again. Do NOT use bags of potting soil, or soil from your garden!

4. Heat: Tomatoes are not as fussy as peppers about heat, but they will not germinate very quickly if they are in cold soil. I like to use plastic heating mats that have a heating element embedded in the plastic. I put my 4 paks of seeds directly on the mats, and I have found that my seeds take between 3 and 21 days to germinate, depending upon how fresh and vigorous the seed is. If bottom heat is not possible, then any warm place is fine, such as the top of the refrigerator.

5. Light: Light is not necessary when germinating tomato seeds. It is essential after the seedlings have emerged, however. I used to grow my seedlings in front of a south facing window. They did reach for the sun, so I turned the plants each day so that they would grow straight. Now I use fluorescent lights, which really gives much more stocky plants. I set the lights so that the growing tip of the plants is about 2 inches from the light.

Those are the main ingredients. Now I will talk you through the process that I use to go from seed to plant in the garden. This will cover the areas of watering, fertilizing, planting depth of seed or plant, use of container covers, transplanting, and germination enhancing. One thing that I did not mention yet is keeping good records of what you grow. When I start, I have an idea of which varieties that I want to plant. I write the names of the tomatoes on sticky labels, and place the labels on the outside of the containers. I fill the containers with the soilless mix, being sure to compress it a bit, since it is fluffy when dry. I then water the cells with warm water, as the mix repels cold water when it is dry. After the mix has absorbed the water, I place 3 seeds of the corresponding variety (watch the labels!) in the cell, gently press into the moist mix (watch the tips of your fingers, as moist tomato seeds tend to stick to skin!), and sprinkle about an eighth of an inch of dry mix onto the top of the seeds. I then mist the cell with warm water to moisten the covering mix, being sure to not dislodge the seed. After planting all of the cells of the 4 or 6-pak, I loosely cover the pak with cellophane, and place the tray on the heating mat. The plastic overwrap helps keep the moisture in the pack. After 3 days to a few weeks, when the seedlings begin to emerge, I make sure to remove the wrap, as it is not good to wet the stem or leaves of the seedling. One thing that can happen to newly emerged tomato seedlings is damping off disease, which is a fungus that rots the plant stem at the soil line. This can be avoided by using new containers each year, using fresh soilless mix for each cell, and allowing the surface of the soil to dry between waterings. For watering after seedling emergence, be sure to water from the bottom, which can be done by setting the pak in a tray of warm water until the surface of the soil darkens with moisture. It is also beneficial to get the new seedlings into the light as soon as possible, either south facing window, or under fluorescent lights.

I do not fertilize my seedlings until they have been transplanted into larger containers, so water will suffice for the early days of growth. It is time to transplant after the seedlings have reached a height of 2 or 3 inches, and have their first and second set of true leaves (the first leaves that emerge from the seed are not true leaves). I like to use inexpensive drinking cups, perhaps 3 inches diameter at the top and 6 inches tall. I label each cup, poke a hole in the bottom to allow drainage, and fill the cups with the soilless mix. I pop the clump of plants out of each cell, being sure not to confuse the varieties if I am growing 2 types in each cell. After gently separating the plants, I poke a hole with my finger in the mix in the cup, and place the seedling into the hole gently, being sure that most of the stem is buried. Since tomato plants form roots along stems that are in contact with soil, this will give the plant a very strong and extensive root system, which will mean less transplant shock when putting them in the garden. I then firm the soil in the cup against the stem, and water with warm water until it starts to come out the bottom. At this point, they either return to the grow lights, or sometimes, depending upon the weather outside, I start the hardening off part. As you can imagine, the outside conditions are very harsh for young tomato seedlings. The sun can scorch leaves, and they can dry out in a hurry. The wind is also tough on their slender stems, and cold another hostile enemy of young tomato seedlings. Gradual exposure to the elements is the key, so putting the plants outside for longer and longer periods of time over 2 weeks or so will result in happy plants. After they have adjusted to transplanting to cups, maybe 2 weeks or so from transplanting, I feed the plants with half strength water soluble fertilizer. Once the plants are 6 inches tall or so, and before flowers can be seen forming, it is time to get them into the ground. But, that is not what this article is about!

Some problems that pop up from time to time are poor germination, strange looking or deformed seedlings, refusal of the seed coat to drop off of the emerging seedling’s growing tip, damping off (which we already discussed), and browning of the new foliage on the tips of the leaves. Poor germination, if all is carried out as above, may simply be a sign of dead or dormant seed. One thing, though, is that you should be patient, as I have had seeds take nearly one month to emerge. Carolyn and I have been experimenting with various means of enhancing germination, such as microwaving the seeds or presoaking in solutions of potassium nitrate or gibberellic acid. While no “scientific” study has been carried out, it is clear that there is something to these seed treatments, and we plan to investigate this more in the future. Deformed seedlings occur from time to time, and often as the plant grows, the situation improves. It is often best to start the seed again, though. One frustrating phenomenon is the stubborn seed coat. It seems to be somewhat variety specific, and age of the seed may also play a role. I have found that using proper heat when germinating tomato seeds minimizes this problem. If you want to chance microsurgery on your seedling in effort to remove the seed coat yourself, be very careful, as it is very easy to snap off the growing tip. Another variety specific problem seems to be browning of the edges of leaves on the young seedling. It is most severe on the wispy, frail looking seedlings of heart-shaped tomatoes. We have found that the plant often outgrows the problem, and we have helped the situation by snipping the brown parts off of the infected leaves. Transplanting a bit sooner and getting the plants into the sun also seems to help them to overcome this problem, which seems to be a seed carried blight. by the way, one thing that is evident after looking at hundreds of heirloom tomato seedlings. There is a lot of variation evident, from stocky vigorous seedlings to frail, hopeless looking specimens, and even different shades of green. Be observant, have fun, and get all that you can out of the experience of growing heirloom tomatoes from seed!