Tomato Red Face: How to Waste Water

When I started this blog, I figured I was a better-than-average tomato grower. I’d picked up a lot of tricks over the years, I said. I also said that tomatoes are super resilient and hard to ruin – which is kind of true. You can do a lot of things wrong and still get some tomatoes, but they may not be very good tomatoes, or the plants may not produce to their full potential – and it’s pretty clear that this is what happened to me this summer.

As I mentioned I’ve been taking some classes through the U of S’s Prairie Horticulture Certificate program and having multiple “eureka” moments about what I may have screwed up this summer, usually based on common but bad advice. While this is embarrassing for me, someone who thought they were so good at growing tomatoes that I could have a whole blog about it, I owe it to you, my 11 or so readers, to talk about the practices I used that were not based in sound science. These posts focus on four specific topics I didn’t understand very well (photosynthesis, plant hormones, nutrient uptake, root development) and why my well-intentioned but misguided practices may have led to my 2020 gardening woes.

Regarding sources – unless otherwise specified, the majority of general plant science information in these posts is based on what I learned in the University of Saskatchewan Prairie Horticulture Certificate courses HORT 13 Applied Botany and SLSC 14 Soils for Horticulture.

Not surprisingly, I followed yet more bad advice and am quite sure I watered my tomatoes incorrectly this summer. I mentioned in previous posts about how most of my 2020 plants appeared to have poorly developed, shallow roots (when in prior years I have nearly thrown my back out trying to get them out of the ground in the fall). Some of this is likely due to the nutrient issues I subjected them to, but underwatering may have also been part of the problem.

The piece of advice I heard this year, which again is VERY common, was that one should let their tomatoes “dry out” between waterings so the roots have to go searching for deeper water. This explanation was specifically called out in my classes as being incorrect science. It’s not technically bad advice, but the reasoning behind it is not accurate.

Roots are not sentient beings or dowsing rods and thus do not go searching for water if they are in dry soil – they simply stop growing. This is how ALL plants work, not just tomatoes. Attempting to force plants to “search for water” and grow deeper roots will actually encourage shallow roots if improper watering practices are used. It’s important for plants to have well-developed, large root systems so they can take full advantage of all the nutrients and water in the surrounding soil – they can’t do this if they’re concentrated in one small area.

A common example everyone has probably heard that it’s best to water your lawn very deeply and infrequently – this is sound advice. If you moisten the soil deeply, it will take longer to dry out (thus less frequent waterings needed) and the roots will be able to grow into the deeper wet layers of soil. If you only moisten the top layer of soil the roots will only grow there, and if you stop watering they won’t go looking for water on their own – they’ll probably just die.

I know I definitely watered my tomatoes less this year than usual. For some reason I was worried that I had overwatered them in the past (even though they always turned out fine), and was trying to be a little more environmentally friendly. I suppose it was a noble pursuit, but didn’t work out so well for me. On the days I didn’t water, I would stick my finger into the soil and check if it felt damp – if it did, I didn’t water. I should have been checking the moisture where I expected the deeper root zone to be, not the first inch of the surface soil.

Depending on the type of fertilizer one uses, it’s also important to water deeply to leach soluble nutrients (i.e. those that are ready for uptake by the plant roots) down into the rooting zone. For example, if you put slow release fertilizer or manure in the top layer of soil, you need water to dissolve the available mineral nutrients and carry them down to the roots where they can be used.

One doesn’t need to water every day – that part of the advice is sound. But when you do water, water deeply to ensure the roots have moist soil to grow into, because they won’t go searching for it

Another important thing to understand about roots is that if they are well developed, they’ll take up approximately as much room under the soil as the plant does above ground. You’ve probably heard this about tree roots – it’s true! This is why burying a piece of pipe beside a tree trunk to be able to water the roots is not particularly effective. The best part of the roots for absorbing water are the very fine tips where the roots have extended and branched out, farthest away from the plant. Watering near the trunk of a tree, or stem of a large tomato plant, does not direct water to the roots best suited to absorb it.

In my attempt to conserve water this summer, I would direct the shower of my hose right at the base of the stem of my tomato plants. In previous years I’d always soaked the entire bed. Now that I’m woke to the above knowledge, I realize that my “environmentally friendly” watering method meant that I was not directing water to the most appropriate area of the root zone – in fact, I was probably promoting dry pockets at the root tips, greatly inhibiting the root growth and thus the ability of my plants to take up the precious water I was so nobly trying to conserve (as well as whatever random mix of nutrients I managed to cobble together with my haphazard “organic fertilization” scheme). Knowing all this now, it’s no wonder my plants had tiny, compact root systems.

The path to Tomato Hell is surely paved with good intentions. But if you really want to be frugal and sustainable with water use, get a rain barrel and stop trying to hack the hose.

Note – when marking this assignment, my instructor commented that copious use of mulch will solve a lot of water problems. I have never been much of a mulcher, but I’m going to make 2021 the Summer of Mulch.

This concludes the Tomato Red Face series! I also created a Soil for Tomatoes guide for one of my other classes, which I hope to post in pieces in the late winter when it’s time to get seeds started. Thanks for reading!

While I’m not proud of any of this, I’m excited to be able to learn from these mistakes. I’m writing this down for myself a) (of course) to fulfill the requirements of my Applied Botany class but also b) so I can identify and remember the bad practices I used so I don’t repeat them in the future. And I am sharing it with you, even though it is a bit humiliating to do so, in case it is helpful for anyone. If you followed any of my bad advice this summer and similarly screwed up your tomatoes, I hope that the hours of effort that I’ve put into these posts might also serve as a sufficient apology.

Let’s grow some better tomatoes in 2021!

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