The volume of a potting container significantly increases the height of tomato seedlings during the first month of growth
Introduction & Background
I thought it might have occurred by chance. Gazing at seemingly motionless tomato plants day after day I started to notice things I didn’t before. I stumbled upon this peculiar pattern by accident after planting tomato seedlings in my basement. It seemed as though the small plastic pots grew tomato seedlings faster than those in smaller seed trays, holding constant the type of potting mix, lighting, and watering. This could have happened to anyone, but it happened to me and I like statistics, plus I had a yardstick handy. To understand how one could even stumble upon such a pattern, or why anyone would grow tomatoes in their basement, first some background.
I had been gardening with my friend and I wanted to grow my own heirloom tomatoes. Naturally, I read several books about growing them. Since I didn’t have a backyard (well I had a 4 x 6 ft cement pad) for a greenhouse, I decided to grow them under eight 40-watt fluorescent plant/aquarium bulbs (48 inch) in my basement. These bulbs are ideal on a small scale, because they emit visible light at wavelengths that are catered to those preferred by plants and do not get very hot. Therefore the relatively low intensities of the bulbs can be made up for by the fact that they can be placed very close to the plants.
Now when one becomes acquainted with heirloom tomatoes, one will most likely want to grow and taste as many different types as possible. I mean have you ever seen, or more importantly tasted, a fresh Southern Night tomato? Or Striped German? The classic Brandywine tomato has got curves that will arouse, and a taste that will keep you coming back. Especially after picking it fresh from the vine. Moreover, today you could potentially grow a wide variety of these unique plants by buying seeds from Seed Savers Exchange on the Internet. Logically, Todd Wilson and I planned to grow as many varieties (this is going on over three years now with eight or nine) as possible.
The first year growing seedlings under lights was a wreck. I planted seeds inside that should have been sowed outdoors. I produced a swamp in my growing tray that propagated fungi (or something which smelled bad), which killed a few seedlings. In another instance, I planted and then watched lettuce grow, bolt, and go to seed without eating it (I didn’t even keep the seed). I still don’t know why. Maybe I thought lettuce just grew then stayed tasty forever. I was very wrong.
The second year I refined my skills and developed a well thought out plan. I would plant one heirloom tomato type and one variety of heirloom pepper. The types planted; the classic Red Brandywine Tomato and the King of the North Red Pepper (both from Seed Savers Exchange). I planted the tomato seed in each container (10.2 x 10.2 x 7.6 cm) and filled it with Vigoro Organic potting mix (0.10:0.05:0.05) I bought from Home Depot.
At the same time Todd Wilson was growing similar heirloom tomato seeds in a basement under fluorescent lights, except he used “seed trays” (or trays with small cylindrical pot holes compacted together) to start his plants. This practice is a mainstay in farming operations in Pennsylvania, in which a large amount of plants have to be grown in a greenhouse during the early spring. Under these circumstances, in may be hard to use a larger container, because of space or potting mix constraints, therefore seed trays are used so that there is a small volume of potting mix (and surface area) per seedling.
During the second year, Todd and I remarked that my tomatoes appeared larger on average than those he grew in seed trays (2.5 x 2.5 x 5 cm) under relatively similar conditions (although differences in heirloom varieties and lighting). A few ideas flew around as to why one set grew faster than the other. Eventually we settled on fertilizer differences (twice I used Miracle Grow while watering the seedlings) or the size of the potting container.
From there I began my search for understanding how to grow tomatoes faster and more efficiently. With more data, I thought, this finding may be used to find the necessary level of potting mix needed for optimal tomato seedling growth, while minimizing excess potting mix use (e.g. volumes greater than X cm3 do not change the average height). Think of the potential – tomatoes a week earlier!
Methods & Results
In April of 2013, I devised a strategy to find out what may have caused the pattern Todd and I observed the year before. I would sow two heirloom tomatoes in a small plastic potting container (i.e. volume = 10.2 x 10.2 x 7.6 cm = 791 cm3) for every one I planted in the seed tray (i.e. volume = 2.5 x 2.5 x 5 cm = 31 cm3). I employed six varieties of heirloom tomato and grew them under the same conditions. In total, I planted 61 tomatoes split 40 in containers and 21 in seed trays. I used Vigoro Organic potting mix and set the plants under an automatic timer that had the light bulbs on for 15 hours a day. I then devised a system so that I could raise or lower the lights to about 2 to 4 inches above the plants to adjust their level as they grow.
I watered the plants as evenly as possible and twice added a tablespoon of Schultz Plant Food plus (20:30:20) (per gallon of water during watering) that I bought at Dollar General probably around 2002. I placed a small fan with a timer on a table across the room, and set the timer to three 15-minute periods of oscillating wind over a 24-hour period. I labeled the containers and trays carefully and took note of the day I sowed the seeds. Also, I usually let tap water sit in an open container overnight, so that it would evaporate off the added chlorine.
After 26 days of growth (April 5 to May 1st) I measured each plant using a yardstick. I placed the yardstick against the base of the plant and measured up to the highest point. All measurements were logged in a notebook.
At a later time, I typed the tomato measurements into a Microsoft Excel spreadsheet, and converted the measurements centimeters. I then broke up the measurements into two groups – containers (volume = 791 cm3) and seed trays (volume = 31 cm3) – which were then broken down further into heirloom variety. These included; Mariglobe, Italian Paste, Mystery Brandywine (seed saved from feral Red Brandywine tomatoes in 2012), Red Brandywine, and Southern Night tomatoes. Average heights were calculated per variety and per potting volume, along with error bars (Figure 1). This demonstrates that within 95% error, the heirloom tomatoes grown in containers with a volume of 791 cm3 were taller than those grown in seed trays with a volume of 31 cm3 (Figure 2).
What if this occurred by chance?
Could this have happened by chance? Definitely. We are certain that we are uncertain about everything. However, can we determine whether or not that chance was so low that it most likely happened because something caused the pattern to emerge? Yes.
For instance, to approximate results from individual experiments we often calculate the average. This has disadvantages and, in most cases, does not reflect upon the reality of the individual data. There is usually a distribution of values, in which some are probably quite different. Therefore, to account for our uncertainty of the true average (if we measured an infinite amount of seedlings) I calculated the 95% confidence error bars. Or rather, the two values that I am 95% certain the true average height falls between (Figure 1). When the 95% error ranges of the two averages do not overlap, can we be sure that the plant height results are really different? Probably. And probably is not good enough.
To me, the height difference could have still occurred by accident. Fortunately the t-test for two sample means exists, and by default assumes that there is no difference between the average plant heights. After conducting the calculations and gathering the results (i.e. t = 4.45, df = 21, P = 0.0004), I can state with over 99% confidence, that the average plant height difference between the two container volumes is significant and has a very low probability of occurring by mere chance (Figure 2).
What caused the average heights to be different?
This is where it gets really interesting. What caused this to happen? I don’t know. I am confident that there is a significantly different tomato seedling height between those grown in potting containers versus seed trays after 26 days in a basement under eight 48-inch fluorescent bulbs that emit light for 15 hours per day. Beyond that is all conjecture.
Currently, I think it is one or some combination of water/nutrient holding capacity of the potting mix, initial root growth dynamics, or how close the seedlings were to the light.
Of the three ideas, I don’t really think it is the water/nutrient issue. I kept the soils moist during most, if not the all, of the 26 days. Plus, I used Schultz’s plant food. This is assuming that there was some limiting nutrient, which is not known to me at this time. Overall, it does not appear to be the problem to me.
The root-growth idea is a more favorable idea of mine at this point. I say that because the sudden growth spurt does not become apparent until about 14 to 20 days of growth. During first week of growth the seedlings are the same height. However, it is during this time that the initial root growth protrudes into the surrounding potting mix. Upon building a proper root infrastructure, the plant can then begin taking up nutrients to grow leaves and a stem. I think that a certain amount or volume of root growth is needed to facilitate an optimal growth rate for the tomato seedling. Restricting the volume of the early root growth is reflected in the poor growth during the first month. On the bright side, though, after the seedling is “potted up” or put into the ground, it would make sense that normal growth rates would probably return.
Alternatively, a new idea is quickly gaining ground as a new favorite. Could this have occurred because the containers were taller (by 1 inch) than the seed tray? This situation is most precisely described by the light intensity equation, which states that light intensity is inversely related to this distance from the source squared (intensity = watts of light/[4 x π x distance2]). So lets say we had an 80-watt source of light directly 4 inches above the potting mix surface in the container (i.e. 391 cm3). Since the seed trays are 1 inch shorter, they would be 5 inches from the light. Using the equation above, the intensity of the 80 watts of light would be reduced by 64%! I conclude from this that the distance from the source of light is especially important during indoor growing, but how much this could account for differences observed in grow rates is not understood (by me, at least). This, again, comes down to a limitation question. Was the growth rate limited by light that was further reduced by the longer distance traveled to the shorter seed tray containers?
On the other hand, in an outdoor greenhouse this should not make much of a difference. This needs further investigation by people who have greenhouses or live in more favorable climates for growing tomatoes outdoors in the early spring. Future research will figure out the influence of light intensity using fluorescent lights at different distances and with a range potting volumes.
This story and experiment has been to show you that using bigger potting container significantly increases the growth rate of tomatoes seedling during their first month of growth. Faster growth rates probably reflect a tomato plant that is more efficiently transforming light, soil, and water into delectable fruits. Gardeners who want to grow tomatoes faster take notice – potting containers are vital!
Eric Morris recently visited BCGG and other gardeners in Pittsburgh. The following is his account of the current state of urban gardening in 2013.
“Here’s an invasive species,” David Pompeani says as he crouches over a garlic bed in the tiny backyard of a 38th Street home in Lawrenceville. “It’s this morning glory that you can’t get to go away. It’ll grow all over your plants.”
Pompeani digs into the ground and plucks the weed from the soil. Although his gardening is now limited to a few beds in a backyard, it wasn’t long ago that Pompeani himself was invading Pittsburgh soil via the act of so-called guerrilla gardening – or gardening on property that didn’t belong to him.
Guerrilla gardening is one form of urban gardening, a practice that has steadily picked up steam over the past several years. Guerrilla gardens, backyard gardens, community gardens and market-based, for-profit gardens continue to pop up all over Pittsburgh, serving the dual-purpose of providing fresh, homegrown produce for local communities and covering the unpleasant blight of neglected properties.
And it’s not just happening in Pittsburgh.
A 2011 report by the American Planning Association discusses the efforts of city governments to recognize the rising popularity of urban agriculture in North America and respond to the needs of the urban agriculture community.
Community gardens can now be found in all 50 states, according to a 2012 survey by the American Community Gardening Association and Rutgers University. Almost 40 percent of the 9,000 gardens listed in the survey were built within the last five years.
And perhaps most telling, part-time gardener Ron Finley became the man of the hour after a stirring 10-minute speech at a TED conference in Long Beach, Calif. in February promoting guerrilla gardening in low income areas. Finley, who has been rejuvenating vacant lots in Los Angeles since 2010, preached the importance of guerrilla gardening for solving inner-city woes. His speech has received nearly 1 million views on TED’s website.
Pompeani and his small group of friends began their gardening adventures in 2010, planting in a vacant lot on 46th Street in Lawrenceville before moving operations to an empty lot on 38th street, not far from the garden he currently operates in his friend’s backyard.
“Red bricks, coal debris, broken glass – those three things are in infinite supply in the soil,” Pompeani said of the small lot before they had cleared the ramshackle plot of land and hauled in the soil. In place of rocks and bricks, the group planted tomatoes and peppers, a raspberry bush, anything they felt like consuming.
Despite obtaining a permit from the city through Mayor Ravenstahl’s Garden Pittsburgh Program and assuming responsibility for the lot for nearly two years, Pompeani was forced from the lot last fall when the city sold the lot that hosted his gardening operation. A house is currently being built in its place.
Since 1950, Pittsburgh has seen its population decrease by more than half, taking a good chunk of its housing along with it. This has created an abundance of vacant lots around the city, sitting unused, revealing blight.
Ed Jacob of the City of Pittsburgh’s Real Estate Division estimates that there are about 4,000 city-owned vacant lots in Pittsburgh, and the city actively attempts to sell all of them, garden permit or not.
“Having a garden permit does not prohibit us from selling a city lot,” said Jacob. “The permit doesn’t create any sort of warranty or guarantee, other than the fact that, yes, this lot is owned by the city and you’re given permission to garden on it.”
Pompeani wasn’t the only one who was sad to see it go. Denise Chirico’s backyard abutted the rear of the garden, which ran the entire length of the lot some 50 feet to the edge of the sidewalk. And it was wonderful, she said.
“It made the lot look so much better. It looked like it was out in the country, that’s how good the garden looked. I think every vacant lot should have that – here in Lawrenceville and everywhere.”
Well, Rev. John Creasy is working on that.
Just a mile and a half away on a hillside in Garfield, on the corner of Wicklow and Cornwall streets, Creasy, associate pastor at the Open Door Church in East Liberty, spends his Thursday nights at the Garfield Community Farm, curating community gardening sessions at the three acre tract of land of about 25 lots that were once vacant.
“It was just completely abandoned land,” said Creasy.
When he began gardening the land in 2008 in collaboration with two other local church organizations, the lots, which once held houses, were owned by the City of Pittsburgh, the Urban Redevelopment Authority and private owners. Creasy and company bought 14 of the lots for $1,000 each and have been granted permission to use the remaining lots through the Green Up Pittsburgh Program, a city-funded program for residents to assume care for vacant lots in city neighborhoods.
The Green Up and Garden Pittsburgh programs are just a few measures that Pittsburgh has taken to give residents a chance to revitalize their neighborhoods while growing their own food at the same time, according to Leah Smith of the Pennsylvania Association for Sustainable Agriculture.
“Pittsburgh has taken steps to really facilitate urban agriculture,”
said Smith. “The city has recently passed new zoning ordinances to help make it legal for people who want to do urban agriculture in the city. They can now sell products directly from urban garden locations.”
And that’s just what the Garfield Community Farm is doing. Now, the garden is home to what Creasy says is “a little bit of everything,” a variety of produce which the group sells to subscribers, farmers’ market patrons and local restaurants.
They also donate amply.
“This neighborhood is really focused on getting food to our lower-income neighbors, so we get food into the hands of the people in our community.”
The Garfield Community Farm isn’t unlike what Mindy Schwartz was doing in Wilkinsburg several years prior.
For Schwartz, what began with a couple tomato seedlings grew into a garden of tens of thousands of them. In 2001, Garden Dreams Urban Farm and Nursery was born on a quarter-acre site of former abandoned properties on Holland Avenue.
“Allegheny County has a program where if you’re a property owner you can buy a side lot for your own use,” said Hannah Reiff, production manager and one of two employees under Schwartz at the for-profit Garden Dreams.
The Allegheny County Vacant Property Recovery Program allows residents to purchase blighted properties for around $4,000 and reuse them as residential side yards, community parcels or affordable housing developments.
Schwartz bought the two lots where the garden sits in addition to the surrounding properties. She owns a total of four buildings on Holland Avenue and Center Street, two of which remain vacant and the other two acting as a tool shed and seedling growing area.
While Garden Dreams specializes in heirloom tomatoes, Reiff says they grow numerous other vegetables including peppers, lettuce, broccoli and rhubarb, all of which they sell to the East End Food Co-op and Whole Foods markets while also offering their produce at wholesale prices to local schools and nonprofits.
So while invasive species try to take over garden beds everywhere, now there are Pompeanis and Creasys and Schwartzes invading vacant lots all over Pittsburgh, crouching to pluck those pesky weeds so they can get back to revitalizing a city and growing the food that fuels.
We have been slow to update our “many readers” with what has been going on in our own garden, so here are some pictures so you don’t have to read anything. You’re welcome.
Well, as they say, a picture is worth a thousand words. You’re probably pretty tired of reading by now. So, until next time let’s garden responsibly.
We are Bridge City Guerrilla Gardens. Let’s bridge the gap between us, our food, and our communities.
As we inch closer to every Pittsburgh gardener’s favorite date, let’s call it “Get Those Tomatoes In Day,” May 15th, it’s not an uncommon occurrence to see little sprouts popping up all over your garden. If you’re on the ball and have some frost resistant seeds in the ground; peas, spinach, or something like carrots, it may be a daunting task to tell the difference between weeds and your desired crop. This can become especially difficult if some weeds get a jump on your sprouts or if you have never grown the selected plants before. To make identification easier, so you can find your swan amongst ducklings, I’ll include some pictures of seedling that are common to direct seed in the garden. Especially one’s popping up right now! Those are the pictures I have. Womp. Womp.
That being said, I have become pretty partial to starting seedlings, when I can, giving the plants a head start on the inevitable weed pressure, allowing me to prep a proper bed, possibly providing a mulch straw cover.
So, here we go:
CARROT (Daucus carota): Delicate carrot seedlings are notoriously bad competitors with weed pressure. It is important to identify these seedlings and eradicate competing weeds.
SWISS CHARD (Beta vulgaris): As can be seen above, swiss chard “seeds” are actually seed pods containing many seeds. It will make for a better crop if you thin the sprouts down to one every foot or so.
BEETS (Beta vulgaris): Notice that the botanical classifications of beets and swiss chard are the same. Swiss chard is actually a beet that over generations and generations had been selected for it’s green rather than the root (interesting right?). , My picture is of golden beets, if you would have your typical red beet, the sprout would have a burgundy tint to it.
PARSNIPS (Pastinaca sativa): These guys are in it for the long run. You put them in early, and you will take them out early in the fall (or later in the winter…or the next spring). These are a commitment crop, so you will want to give them a great start. They come up looking, well, about likr everything else around them. They have two leaves going in either direction. The difference between them and my weeds were their vibrant green color. They will eventually form their true leaves, which looks like a parsley leaf, or like celery when it forms its true leaves
SPINACH (Spinacia oleracea): The initial leaves are long and skinny, but eventually a broader rounder leaf will form…In the shape of spinach. Yum.
PEAS(Pisum sativum): These are great, for a number of reasons. You can get them in early, they fix nitrogen, and they taste great!
Alrighty! Get weeding. Make sure you leave those beautiful swans alone, and get rid of only the ugly ducklings.
This is an extremely abbreviated list, but if you have any requests, I can set up a photo shoot (If the lighting is just right), and try to weed out, well…the weeds.
Until next time, let’s Garden Responsibly Pittsburgh.
We are Bridge City Guerrilla Gardens. Let’s bridge the gap between us, our food, and our communities.
Last night I attended an awards dinner held by the Thomas Merton Center (TMC) honoring Dr. Vandana Shiva. She, upon receiving the award, joined a list of distinguished awardees including the likes of: Joan Baez, Howard Zinn, Studs Terkel, Wendell Berry, Amy Goodman and Noam Chomsky.
I’m not going to sit here and write a post that tells you all about Dr. Vandana Shiva and how great she is (She is amazing by the way). If you want to know you’ll find out, and anything I say isn’t going to change that. I just thought you should get to know that she’s out there. There are people that haven’t given up the good fight and she is one of them.
I’ll start this post as my night started. Just to get you in the mood. So, yeah…it started with the musical stylings of Deewane, Carnegie Mellon University’s premier South Asian all-male a cappella group, performing “This Love” by Maroon 5. Bizarre. (I couldn’t find the their version online, but just so you can get a sense of the song: There you go) Wowee. I can not get over this song choice. What? Really? Maybe it lightened the mood. I don’t know. I was just confused. I think I saw Vandana Shiva dancing….Not really.
Anyway, what I’m going to do, is tell you what Dr. Shiva said about gardening.
Different forms of food production can not be talked about without at least thinking about modern industrial agricultural. Shiva described, “One of the things that has happened, with industrialism on the one hand, and the rule of capital on the other is the perpetual message as human beings you are incapable. You can’t grow food. You can’t have a home. You can’t build a community. You can’t have freedom. All of that will be provided to you in the package and recipe that we will decide.”
She is right in too many ways. She is not saying that industry and capital are making all of our decisions, because they are not, but they are making it increasingly harder to make the decisions we want to make. When these decisions come all the way down to the nourishment that we are putting in our bodies, it blatantly becomes a time to stand up and say “no!” No, I don’t want that. But, that’s not enough. You have to say “yes!” Yes, I’m willing to do something. What should I do? I’m not sure, and I ask myself that question every single day. We all know a generalized version of Newton’s the law of motion, ” For every action, there is an equal and opposite lobby that makes that action irrelevant.” Well, that’s not exactly right, but it surely feels like it.
Wendell Berry, a past TMC award recipient said, “Eating is an agricultural act,” and if we stop eating processed, commodity food-like substances this industrial system on which we depend might change to take the person eating the food into account. Even if it doesn’t happen immediately, it doesn’t prevent anyone from producing their own food. We can implemet our own “subversive plots.” Subversive garden plots.
“I really feel that the garden is the future,” Shiva continued and she went on to say that when you are a gardener, ” You produce abundance. You produce beauty. You produce nourishment. A gardener doesn’t conquer, a gardener serves.”
You serve your personal health, you produce fresh vegetables, and divert at least a portion of your diet away from industrial agriculture, and you create beauty in a site that can really bring people together. The way we eat is going to have to change. Any way you look at it, we are eating unsustainably, and I am not saying that I am better, or that I’m even close to eating or being sustainable, I’m just saying I recognize that we can’t go on like we are into eternity. Change may not be an immediate thing, but taking steps now to make a transition easier can’t be a bad thing (I was going to equate this to the steps of AA but their steps sort of freak me out). Let’s manage the unavoidable, but avoid the unmanageable. Our seemingly irrelevant decision now could mean really hard times for a lot of people. I know a lot of us are holding out for some sort of rapture (fingers crossed), but that date has passed how many times now?
Dr. Shiva finished her speech by quite frankly stating, “Within one hundred years we could push ourselves to extinction. That is not an option.”
You can follow Dr. Shiva on Twitter @drvandanashiva
and now you can follow Bridge City Guerrilla Gardens @bridgecitygg
We are Bridge City Guerrilla Gardens. Let’s Bridge the gap between us, our food, and our communities.
In the beginning God created the heavens, the earth, water, land, people, animals and He needed a break (I would really have liked to see sandwiches as a priority…What can you do?). Before the break God said,
“Be fruitful and increase in number; fill the earth and subdue it. Rule over the fish in the sea and the birds in the sky and over every living creature that moves on the ground.”
Humans took this advice very seriously! Being city dwellers, we live everyday amongst and on top of an island of cement in close quarters with our neighbors, and that’s why a lot of us like being here. Our neighborhoods, the earth under our feet, have been subdued. In one way or another, whether it be development, chemical intensive agriculture or a plethora of other circumstances the earth has been subdued. We can get any produce, any time of the year for really cheap. Bridge City Guerrilla Gardens (BCGG) will discuss the benefits and opportunities of producing your own food and what it means for the future.
Pittsburgh has unique opportunities for individuals to get out, rejuvenate, bring beauty, and productivity to vacant and abandoned green spaces. These projects also give individuals opportunities to spend time in their neighborhoods, getting to know people living in their own communities in healthy and productive ways.
In the coming posts we are going to:
-Lay out a step by step process of finding a gardening site, and getting a “Garden Waiver” from the city. We will be sure to address questions and concerns that may arise. (Where will I get my water? Is this soil toxic? Am I allowed to be doing what I’m doing? etc.)
-Find cost effective and space effective composting techniques for all living situations. We will try to address issues concerning composting such as: Why? How? What? Where?
-Publish seed saving techniques for a wide variety plants.
-Have locally produced, seasonal recipes.
-Discuss the benefits and opportunities of producing your own food and what it means for the future.
Lastly, we will address any questions or concerns that you have about anything we are doing.
Bridge City Guerrilla Gardens wants you to know that you can live in a city, you can have a garden, you can produce your own fresh vegetables, compost, save seeds, rejuvenate soil and its not as hard as you might think.
We are Bridge City Guerrilla Gardens. Let’s Bridge the gap between us, our food, and our communities.