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Growing Food With Greg: Growing tomatoes — direct seeding vs. transplants

Tomatoes are the star of most people's vegetable gardens, including mine. This year, I decided to see what grew better — tomato transplants or plants that I seeded directly into the garden at the beginning of May.
These Rutgers tomatoes were moved from the cold-frames about three weeks ago. The tallest are 22 inches high. (GREG AUTON)

Tomatoes are the star of the show in most people's gardens. We love our gardens, and everything in them, but few gardeners are more prideful or boastful about any other plant. In today's article I will discuss different strategies for growing healthy plants based on some experiments that I did this year in my garden. I think you will be fairly surprised at the results!

Whether it is their vibrant red colour, their wonderful flavour, or the pure hubris fooling a tropical nightshade (many nightshades are toxic) to grow in a northern climate, tomatoes inspire vanity in food gardeners like no other plant, and I am no exception to that rule.

I love tomatoes, and I wait in eager anticipation for the joy of eating the first tomato that I am able to pluck from my own vines. For me, it's all about the flavour. There is no comparison of the difference in flavour between store-bought tomatoes and home-grown. I find it so stark that I rarely buy tomatoes out of season because I find that for the most part, while they have the colour and the shape, the flavour just isn't there, and even when they are 'good' — they are in a different category of 'good': store-bought good — the best of the not-so-good.

The problem: A short growing season that isn't very hot

So, we love tomatoes and we all want big healthy plants that produce as many as possible — but there's a problem: it's cold here in Canada, and in some parts of Canada, the growing season is short and not very hot. This makes is difficult in some areas to trick a tropical plant into thinking that it's south of the border long enough for it to bear fruit.

Conventional wisdom

The conventional wisdom to planting heat-loving plants in a cold climate is to choose varieties that have shorter maturity times (for tomatoes that means growing bush/indeterminate varieties), and to grow them indoors for a month or two prior to the last frost date, or to buy transplants from a garden centre, and then to plant them once all risk of frost has passed.

The first of these suggestions is solid advice, and I advise anyone growing tomatoes where summer comes late and is not very hot, to heed it without question.

The second is also good advice and works fine, but I have never liked dealing with transplants. Growing your own transplants is labour intensive and all that work can be for nothing if you move them out too quickly, do not harden them off properly, or plant them in the ground when the soil is too cold.

These are all especially big problems for impatient optimists (like me). Buying transplants is a little more sure-fire, takes less work, but costs money, offers limited options to the gardener in terms of variety, and can also be all for naught if you plant them out too soon. Finally, transplanting involves extreme shock to the plant, and it is typical for a transplant of any kind to simply stop growing for multiple weeks after being moved, while it adapts to its new, harsher, outdoor environment.

071517-tomatoes-2These store-bought transplants are about 18 inches high as of July 14. A month ago, they were nine inches high. They didn't grow at all until about three weeks after they were planted. I fully expect the cold-frame tomatoes (see below), despite having germinated a month later than these, to outgrow and out-produce them as the season progresses. (GREG AUTON)

A new hope

This season, I tried something new and the results have been great so far. I stepped back and thought about two things that I have been noticing in recent years.

The first is that, while some plants are more able to withstand being transplanted than others, no plant likes being moved, and they all stall out for a certain amount of time with they adapt to having been moved.

The second is that tomatoes are tropical plants, and they need to feel that they are at home, and not in Canada. The problem is this: they need to be directly seeded in the ground where they are going to grow outdoors, but wherever this is, it needs feel like June in May, and like July in June. The answer was obvious — direct-seed them on May 1 in a cold frame.

In early May, while it can still easily get down to 0°C or below on any given night, the cold frame can get up to 30°C during the day and keeps the soil from freezing at night. This means that your tomatoes will germinate in a week or two, and will get along just fine in their makeshift "bio-dome" home.

If your soil level is close to grade, you will only need to water once a week (or less if there is regular rain), because the roots will be able to find groundwater easily, and this also makes it easier than messing around with transplants. As the season progresses, you leave them in there until the plants hit the roof (sometime by early July), and then you just remove the roof, mulch, and let the rain do all the work. In this way, during the hottest part of the year (July/August), you don't have to worry about them over-heating because the roof is off.

071517-tomatoes-3These Rutgers indeterminate tomatoes were direct-seeded into the ground in these cold frames on May 1. They are now the tallest tomatoes in my garden at 25 inches. When I bought my transplants, which were 9 inches high at the time, these were only a few inches tall.

Problem solved!

The real advantages of starting tomatoes this way speaks to how successfully this technique addresses the key problems that I mentioned earlier:

  1. The tomatoes are warm enough to germinate outdoors in the ground where they are going to grow.
  2. The cold-frames extend the tomato growing season by allowing it to begin earlier.
  3. Because you are direct-seeding, you can plant any variety that you want.
  4. There is no need for hardening off. Whether you are growing under plastic or glass, the plants have no problem adapting once the roof is removed. The soil temperature remains quite stable from July onward, and the range in temperature from day to night is tolerable, and not unlike the highs and lows they have experienced thus far, because under glass in May, they would have experienced night temperatures as low as 5°C, as well as day temperatures as high as 30°C.
  5. The plants stay where they were planted. This means no setback from the shock of being moved, resulting in healthier plants, accelerated growth, and earlier and more bountiful yields.
  6. Growing them this way also saves the electricity, space and materials that would have been required by whatever makeshift grow-op you would have constructed/bought to do it indoors.
  7. You can move some of the cold-frame plants to other parts of your garden when thinning in mid-June. As a result, these plants will mature later than the ones that were not moved, thereby extending the length of your harvest, and allowing you to grow more plants than the size of your cold frame would otherwise have allowed.

Final thoughts

So that's the trick: build a cold frame this fall. On May 1 (or earlier if you feel lucky), put some seeds in the ground. Water once a week (or less if there is regular rain), and then take the roof off in July. I suggest dimensions of approximately 72 inches wide, 24 inches from front to back, 12 inches high in the front and 18 inches high in the back, with a sloping transparent roof (plastic/lexan/glass). Position the cold-frame so that the slope is facing southward, and then count the days until next spring. The tomatoes that I planted using this technique have outperformed all the other tomatoes in my garden this year, so I think I have a winner, and my tomato grow-op days are over!


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Greg  Auton

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