Any reader will find among the pages of gardening books, magazines, and websites dozens and dozens of suggestions, tips, and hints that may sound rather unbelievable. I like to call these gardening urban legends, often unproven but, for whatever reason, adopted by this or that gardener and then passed along as folklore during discussions with friends and neighbors. I’m sure many great ideas are included, as well as procedures that are most effective in a specific locale, but some of these “tips” are just money-making scams. The information age has done both great and awful things for our knowledge. In gardening (as with money-making schemes), if something seems too good to be true, it probably is. I’ve found through the years that much of what works in growing tomatoes is common sense and easily reasoned.
This chapter consists of a list of various tomato-related myths, urban legends, and off-beat theories that I’ve collected through the years, along with my experience with or assessment of the approach. But I’m also still learning all the time, so read them, process them, and reason my assertions, and then make up your own mind.
Why not try testing some of these theories yourself? If you do, remember to carefully control the experiment. Try to use the same variety of tomato in the same type of garden environment in close proximity, to ensure that the only thing you’re doing differently to one of the plants is the practice you’re testing; in other words, introduce only one change, or variable, and treat each plant the same throughout the growing season. I’ve often read about the placebo effect in play as the cause for the noted improvement — if you really believe something should work, the desire to see the effect overcomes objective evaluation. In some cases, the tested plant may be just slightly more coddled or cared for, and it becomes that little bit of extra care that makes it seem like something is working, when it really is not.
Is it risky to grow non-hybrid/heirloom tomato varieties? Will they get diseased? Is it safer to stick with hybrid varieties?
Not necessarily. It depends on your goals. In general, many hybrid tomatoes were bred to handle various diseases (see Tomato Diseases). Flavor was often not the primary goal, setting up what seems to be a trade-off between yield and flavor. The response to this question has many dependencies, all related on how and where you garden and your particular goals (variety, yield, flavor, or seed saving as examples).
I was so interested in this topic of hybrid versus heirloom that I undertook a detailed study, the results of which can be found in The Great Competition. My conclusion was that the heirloom varieties I grew equaled, and in many cases exceeded, the performance of most of the hybrids. What is most important is to understand the goal of your garden, try different varieties and approaches, and make future changes based on what you experience.
Is the “Tomato Potato Plant” I saw advertised in the Sunday paper for real? Sounds like a great way to get both from the same plant.
If it sounds too good to be true, it probably is. I’ve seen Sunday newspaper inserts through the years offering a plant that has tomatoes above and potatoes below, or bush-type tomato plants capable of immense fruit or 100-pound yields. My experience tells me that it is best to avoid such offers, or at least to approach them as curiosities only if you are willing to part with the money it takes to purchase them.
Since potatoes and tomatoes are both from the Solanaceae family, it is possible to graft a tomato “top” onto a potato stem. (I’ve also read of rooting tomato stems inside potatoes.) But there are so many potential issues with this that it’s hard to see why a person would want to dedicate valuable garden space to the endeavor. The potato gets the energy needed to produce potatoes by producing rampant vines. If a tomato plant top is grafted onto a potato plant stem, one root and vascular system is now responsible for the nutrition needed to produce two crops — the potatoes below the soil, and the tomatoes on the top growth. I’d love to hear the results from anyone who gives it a try and compares yields of potatoes and tomatoes of the same varieties from normally grown plants.
To make matters worse, potatoes often produce seed balls that look like small tomatoes and are very toxic — mistakenly eating one, thinking it was a cherry tomato, would be a very bad thing to do for your physical well-being. Finally, potato plants are magnets for the potato beetle. The beetles would be just as happy to munch on the close-by tomato foliage as on the harder-to-find potato foliage.
It is hard to keep up with all of the over-hyped gardening merchandise, typically advertised in Sunday-paper inserts (which seems to be where they first appeared many years ago) and now also found in popup Internet ads or on garden blogs and websites. Exaggerations of fruit size and plant yields are nothing new, as a look through old seed catalogs (dating into the mid-1800s) confirms.
Can I sow tomato seeds outdoors in the winter? I’ve heard that this is a great way to get an earlier harvest with less work.
It depends on the length of your growing season and which varieties you choose to grow. Winter sowing is the process of planting tomato seeds outdoors in containers at about the same time you would plant them indoors. The concept is that the weather experienced between planting and spring will provide well hardened-off, hardy seedlings, without the need to purchase and set up the materials used for indoor seed starting. In a way, many of us observe winter sowing in action when we notice that seedlings sprout in the spring in the containers or garden areas from last year. Perhaps some tomatoes or peppers fell off the vine and rotted on the ground, and when the conditions warmed and became appropriate in the spring, there was germination. Many of my seedling customers return to me to tell tales of seedlings of tomatoes popping up throughout their gardens, and they wonder what they are and whether they will grow. Winter sowing is a way to control that process so that you are confident of the varieties that pop up. If you are unable to start your own tomato seed indoors, winter sowing may be a good solution for you, given a long enough growing season.
Direct seeding is a variation on winter sowing; the timing and location are different. With winter sowing, you begin when it is still essentially winter and create a somewhat protected location into which you do all of your sowing in various containers. Direct spring sowing is planting seed in place where you will grow the plants to maturity. This certainly is a method that can work in long-season areas, or to extend the season; the seeds will germinate, and as long as you don’t have a late and unexpected frost, they will grow on, become hardened off naturally, and produce full-size plants, but only where the season will allow before the killing frost; you are essentially cutting a few months from the plant’s life cycle, since the two months from seed to a plant ready to be set out will be happening in the garden. Each year, it seems that a few tomato seedlings from dropped fruit escape my detection and produce surprise plants, though it seems to be most common with cherry tomatoes. The variety Mexico Midget appears here and there throughout our yard each season, much to the delight of our chocolate lab, Buddy!
If I grow tomatoes next to each other, will they cross-pollinate and produce fruits that will appear as a cross of the varieties?
No. A tomato plant of a given variety will produce that variety, even if some of the flowers get crossed by bees with pollen from another variety that season. Seeds saved from such crossed tomatoes, however, will produce hybrid plants the following season, which will likely appear to be very different.
If I separate tomato varieties in my garden by a large distance, will that guarantee that the tomatoes will not cross-pollinate?
Separation helps but is not a guarantee; it depends on what the bees do. Tomatoes are one of the best plants for seed savers because they tend to self-pollinate the vast majority of the time — over 90 percent. Even if curious bees visit open flowers, the pollination deed has likely already been done. But likely isn’t always; consider the time it takes a bee to move from one corner of a 100-foot-long garden to the other, and you will understand that separation doesn’t provide a guarantee of purity. Growing other flowering plants between varieties will reduce chances of crossing.
The only way to truly guarantee that tomatoes will not be crossed by bees is to use a physical barrier to isolate flowers. You could try securing a homemade sack of a very light, air-permeable material such as row-cover fabric around an unopened blossom cluster, or use a cage that is wrapped in screening or row cover fabric. I plant my tomatoes very close together and grow out thousands of seedlings each year, and find that by saving seeds from the earliest fruit (whose flowers would have been self-pollinated early, before the bees took much of an interest in the blossoms), my seed purity is greater than 98 percent. If you choose to not use a physical barrier but want to save seeds, be aware of the bee population in your garden. Save seeds from fruit that started to develop before the bees’ arrival, or wait until late in the season, when bees find other types of flowers to keep them busy.
Will setting up a fan to blow on young tomato seedlings cause them to develop sturdy stems and end up hardier?
It can’t hurt. Air circulation certainly benefits the health of very young tomato seedlings by reducing the incidence of fungal diseases caused by stagnant, humid conditions. Toughening up the plants by aiming a fan at them is often mentioned. And, in fact, in a study done at Cornell University, lightly brushing tomato seedlings (with a broomstick or plastic pipe) was shown to slow the rate of stem elongation, leading to sturdier, stockier plants.
Personally, I’ve always felt that nature provides the perfect solution: a nice, gentle spring breeze. But plugging in a fan certainly can’t hurt either.
Will sticking a copper wire through a tomato plant stimulate the plant defense mechanism through an electric charge?
No. The premise is that either through movement of copper ions into the plant vascular system or through some effect of a charge built up through the copper wire, some protective properties are transmitted to the growing tomato plant so that it is less likely to suffer from disease. The procedure involves passing a copper wire through the lower stem of a young tomato plant and passing part of the wire into the ground. I’ve also found variations that include spraying the copper wire–treated plants with 3 percent hydrogen peroxide. As a scientist, I can’t come up with a basis for the effectiveness of this treatment. Most people who tried this reported no difference, and as with all of these types of unique or unusual remedies, a very few report high effectiveness.
Will injuring some tomato foliage early on cause the plant to create its own disease-fighting agents and help the plant be healthier?
No. The idea is that crinkling or otherwise maiming some young tomato foliage will cause the plant to fire up its defense mechanisms, which would hopefully lead to being able to fight any disease that comes to infect the plant. Unfortunately, there is no sound scientific basis for such a phenomenon. Indeed, intentional injury to tomato foliage produces an easy entryway for disease.
Will pruned tomato plants produce larger fruit than unpruned plants?
In my experience, no; the size of a tomato is controlled by its specific genes. Any variety will grow as large as it can when it’s given optimum growing conditions.
Will removing all of the foliage from the plant increase the production, flavor, or quality of the tomatoes?
No. In fact, this is detrimental. The removal of all foliage from tomato plants is an invitation to numerous issues and will significantly reduce the quality of whatever fruits manage to grow to maturity. With no foliage to shield the tomatoes from the searing heat of summer’s direct sun, sunscald would have a significant impact on most, if not all, of the tomatoes, ruining the quality. Tomato flavors develop because of photosynthesis going on in the leaves. One of the reasons that indeterminate tomato varieties are generally more intensely flavored than determinate varieties is the vastly increased leaf area, which allows far more chemistry to go on in the plants and results in increased flavor. This is thought to be the reasoning for the generally superior flavor of indeterminate tomato varieties when compared to determinate types.
Will using leaf or grass mulch around the base of the tomato plant allow for the formation of substances that fight some of the various tomato afflictions, leading to healthier plants?
No. As a physical barrier that prevents spores from potentially diseased soil from splashing up onto the lower foliage of the plants, mulch is a very effective tool that contributes to a healthy garden. Mulching also helps to slow down water loss from the soil on very hot days, which can help reduce the formation of blossom end rot. As mulch breaks down it forms humus, which acts as a natural fertilizer for the plant. But there is no direct evidence that mulch itself leads to the formation or existence of actual disease-fighting or disease-blocking compounds.
Will allowing my tomatoes to sprawl, uncaged and unstaked, result in greater yields?
In theory, yes, but many factors will negate the advantages. Sprawling tomatoes are certainly easier to manage, and it makes sense that just letting them go will allow them to produce enormously. There are many caveats, however. Most soils contain various bacterial, viral, or fungal agents that can harm the tomato plant and fruit in various ways, so yield is easily compromised by disease, if and when it hits. A good layer of a barrier substance, such as straw, leaf mulch, or non-treated grass clippings, is necessary to keep the soil off the tomato foliage and fruit. Even still, mice, voles, and slugs can do great damage to the tomatoes. A tomato cage, allowing vertical, cleaner growth, achieves the same sort of yield with less potential loss from disease. Sprawling plants are also a potential logistical problem in terms of getting in to harvest the tomatoes without stepping on and injuring the plant. Varieties can also get easily confused, which is detrimental to accurate seed saving. Indeterminate tomato vines can easily reach 10 feet or more in a long growing season, and all of those side shoots (a.k.a. suckers) will reach nearly as long. This explains both the incredible yield potential and the tangle of tomato plant that will likely result.
Do those Topsy Turvy containers really work?
This novelty works reasonably well, but only for small-fruited tomatoes, with frequent watering. The Topsy Turvy is a name brand of a widely advertised hanging planter with a simple premise — the plants are grown upside down, with the seedling emerging from the bottom, roots upward, watered from the top, and hung from a secure hook. This can be considered a space-saving and unique way to grow plants, and it does work.
Strawberries, which produce numerous runners, may do quite well in such a container. Training flowers such as some petunia varieties would be lovely in one. But it is very limited in its use for eggplant because of the upright nature of the growth and vigor of the plant, and it is essentially useless for the fragile-stemmed sweet peppers, though it actually works to some degree for tomatoes, with two significant caveats: A Topsy Turvy device doesn’t hold much soil, so it is limited to one tomato plant for any hope of a decent yield. And because larger tomatoes become heavy as they ripen, a single cherry tomato plant is probably the best use. I planted a single Sun Gold plant in a Topsy Turvy a few years ago and hung it off my deck. As long as I kept it well watered, it thrived, and it hung 8 feet down to the ground, producing a decent crop of tomatoes along the way. Our dogs, in particular, thought it was a splendid idea, especially when tomatoes started to appear at ground level.
Will leaving my grow lights on for 24 hours a day result in healthier tomato transplants?
No. In fact, this practice can be detrimental. “More should be better” is a common supposition. If tomato seedlings benefit from grow lights, then the longer they are on, the happier the seedlings? Well, no. Keep in mind that plants in nature receive a break in the action between sunset and sunrise. Research indicates that the optimum amount of time for tomato seedlings to be under light is 14 hours. No additional benefits are seen between 14 and 20 hours, and possible detrimental effects are seen beyond that (the theory is that a buildup of excess starch and sugars in the foliage promoted by the nonstop light leads to foliage damage).
I turn my grow lights on when I wake up and turn them off when I go to bed, which provides light between 8 a.m. and 10 p.m.; this has worked fine for me. It isn’t necessary to be absolutely specific about the start and end times, so you can fit this to your own particular morning and evening activities. A timer can be very helpful if your schedule is not predictable.
Is transplanting my tomatoes really necessary?
Transplanting is strongly recommended. Transplanting seems to be the norm for the gardeners who start their own tomato seeds, though it is true that, in some climates and for early varieties in particular, direct seeding can work. Often, we find in our garden volunteer plants from the previous season’s dropped tomatoes that emerge once the soil warms and, if we leave them be, turn into fruiting plants. This then raises questions of whether one needs to transplant.
For most of us, transplanting is a necessity because volunteer- or direct-seeded seedlings wouldn’t nearly match the yields of those plants that get their start indoors. In addition, transplanting allows for very vigorous and healthy seedlings, due to root development along the part of the stem that is buried during the transplanting step (see Should You Transplant?).
Will my garden be more successful if I plant by the phases of the moon?
Evidence of success are anecdotal, and those who abide by it are passionate. I’ve not tried it myself. Planting governed by the phases of the moon seems to stem from a long-held belief that the moon controls moisture, a principle dating back to Pliny the Elder in the first century C.E. How this theory extrapolates to when we do specific tasks today depends on the beliefs of the individual gardener. The guidelines indicate that the various phases of the moon will be beneficial to different gardening tasks, whether it be seed sowing, planting, or weeding. As always with suggestions that seem to be more legend or myth-based than science-based, these provide great opportunities for small projects so that you can explore for yourself which ones do or don’t work for you.
If I save seeds from the first tomatoes that ripen on a particular plant, and I do this for several seasons, will I end up with a tomato that is earlier than the one I started with?
No, since the genetic material in all seeds from all tomatoes on an uncrossed, open-pollinated plant will be the same.
If I save seeds from tomatoes with blossom end rot (BER), will all of the tomato plants from the saved seeds produce tomatoes with that affliction?
No. If a tomato variety is open pollinated, all of the genetic material in each seed in each fruit on a plant is the same. A physiological issue like BER is a result of the conditions experienced during the formation or ripening of the fruit, not of anything genetically distinct about the particular affected tomato, so seed saved from a fruit with BER should be fine. The only exception would be if every single fruit on the plant, and other plants grown from the source seed, suffers from BER; then it is possible that something genetic about the variety is making it prone to developing BER.
Should I remove all suckers from a tomato plant? I’ve heard that they sap energy from the plant.
No, they don’t sap energy. In many cases, leaving some or all can be beneficial. It was actually the suckering topic that gave me the idea of dedicating this chapter to tomato myths and urban legends, because I get more questions about sucker removal than just about anything else during our spring seedling sales. I cover side shoots/suckers in depth in To Prune or Not to Prune?. The short answer is that suckers are simply additional growing stems and do not sap energy from the plant. Indeed, there are more reasons to keep them than to prune them.
Will shading my tomatoes to reduce the temperature or using calcium spray on the blossoms prevent blossom drop and increase the chances of a good crop?
These practices have limited effectiveness at best. Each particular tomato variety has a temperature and humidity range that facilitates pollination of the flowers and therefore fruit set. Tomatoes from cherry to medium size seem to be far less fussy and yield more reliably over a wide range of conditions. The large, irregularly shaped beefsteak tomatoes can be fussier, though it is variety specific. Tomato flowers should, in theory, pollinate as they open, from the brushing of the pollen-releasing anthers against the receptive tip of the pistil. Though it is impossible to control the humidity experienced by a tomato blossom growing outdoors, screening on a very hot day could provide a microclimate sufficient to increase the probability of pollination. To the tomato grower who is salivating at the thought of the crop to come, any simple efforts such as these are worth a chance.
The various hormone and calcium sprays that are applied directly to the blossoms are another story entirely. They are intended for use primarily to promote pollination and fruit set in cooler climates, and their effectiveness in the more problematic hot, humid conditions is likely very low. And even in those cases where fruit set succeeds, the resulting tomatoes tend to be seedless (parthenocarpy), resulting in unpleasantly mealy, even bland fruit that don’t approach the quality of those that pollinate naturally.
My tomatoes won’t set fruit! Is that because there are no honeybees?
No. I hear this comment frequently each season during our seedling sales. Many of my plant customers find that their tomato yields are lower than they had hoped, and since many yards are short of honeybees it can seem like a correlation. First, honeybees are not particularly attracted to tomato flowers (many other bee types are, though). Second, tomatoes are self-pollinating, and the deed is typically done as the flower opens, meaning bees are not needed. More important is a much-overlooked fact: the often unrelenting heat and humidity of the summers, particularly over the last decade. Lack of tomatoes is a result of excessive temperature or humidity experienced during the flowering of the particular variety.
I have a lush, healthy plant with no fruit at all. What’s wrong with it?
Most likely the blossoms dropped before fruit set. When a tomato plant is healthy but fruitless, three explanations are possible. If absolutely no blossoms are produced throughout the entire season, the plant is a “mule,” possessing a rare genetic mutation. In all the years I’ve grown tomatoes, I’ve observed this only a couple of times. Far more common is the impact of weather conditions. Perhaps the plant produces flowers regularly along the vine, as it should, but the flowers shrivel and drop off, leaving no tomatoes at all. This phenomenon is quite common during very hot, humid periods with the large beefsteak-type varieties (it is highly unlikely to happen to small- or medium-fruited varieties), particularly if the plants are heavily pruned, leaving only the main growing stem. Since the numbers of flower clusters will be limited, if the conditions favored for pollination for many of the clusters are unsuitable, the result could be 8 feet or more of very little harvest. The best way to avoid this issue if you want to grow large-fruited tomatoes in a hot climate is to hedge your bets on the weather: cage or only minimally prune the plants and/or stagger the tomato plantings so that the varieties you desire are flowering throughout the growing season.
I’ve heard reports that overly fertilizing tomato plants (especially with an excess of nitrogen) will actually lead to an excess of vine and a relative lack of tomatoes, but I’ve never observed this in my gardens. The goal of a tomato plant is to create seed, so that it carries on from generation to generation; the flowers, and subsequent tomatoes, should happen, given appropriate weather and plant nutrition.
Will getting water on the tomato plant foliage lead to disease or damage from the sun’s hot rays on the beads of water?
Damage from the sun is unlikely, but promotion of disease is possible, especially if soil gets splashed on lower foliage. Rain in cool weather can also lead to late blight, if the disease agent is present. Many tomato gardeners do everything they can to prevent wet tomato foliage, but consider what happens to the plant in a heavy rainstorm. It isn’t so much about wet foliage as it is about what may be splashing on the plant that could cause harm. Since many tomato diseases are embedded in garden soil, the most important thing is to prevent soil from splashing up onto the lower foliage by mulching well around the base of the plant. Watering large tomato plants from above is potentially wasteful, as the water cascades off the foliage but, especially if the plant is large, may not provide the deep watering that the plants require. I’ve experienced no issues at all with watering flats of tomato seedlings from above using a gentle spray. But once a plant is seated in its final location, be it pot or garden, it is far more effective to water around the base of the plant to allow for a good soaking of the root zone.
Is it true that the tomatoes on my plant won’t ripen if they’re hidden by the leaves?
No. Tomatoes ripen when they are good and ready, informed by the particular genetics of a given variety. Weather will certainly play a role, but the location of the tomato on the plant doesn’t impact its ripening time at all. In fact, exposed green tomatoes that become roasted by direct sun in the middle of the summer are prone to sunscald. The main problems with deeply hidden tomatoes are the propensity to actually miss them when they are ripe and the opportunity for increased pest attacks because they are more difficult to monitor.
Do I need to vibrate my tomato blossoms or shake the plants each day to get good pollination?
This isn’t necessary, but it could help if the plants are grown to maturity in greenhouses.
The principle behind shaking or vibrating tomato blossoms is that the flowers may need a bit of help to ensure that the pollen from the anther is captured by the tip of the pistil to ensure fruit formation. This is a common practice with greenhouse tomato growers, since there are no natural breezes to move the flowers. It shouldn’t be necessary to vibrate tomato plants grown outdoors.
To test the effectiveness of this practice, it would be interesting to have the same tomato variety side by side, and to vibrate each flower daily (or shake the entire plant — gently, of course) on one plant and totally ignore the other plant. Be sure to collect information on numbers of tomatoes set and total fruit weight. If you do this, I’d love to know how the experiment turns out.
Should I pinch all blossoms from my transplants, so that the energy goes into the plant, not the first tomatoes?
No. The supposition of this garden myth is that if you have transplants that possess buds or open flowers, or even small set fruit, all of these must be removed when the transplant is set into its final location so that it puts its effort into establishing the plant, not dealing with maintenance of the flowers or tiny fruit. My personal experience is that the plant knows best, and I’ve often gotten some nice early tomatoes (far in advance of posted maturity dates) by leaving any flowers or fruit as I settle the transplant into its resting place. I’ve observed no delay or setbacks with the establishment of the plant; grown side by side, there is no difference in the health or size, over time, of plants with or without flowers and fruit when planted. In my opinion, all you are doing by plucking off those first flowers and fruit is delaying gratification. But, as in the case of the myths that are easily tested in the garden, it is better to “do the experiment” and find out for yourself.
Are tomato diseases passed along on seeds?
Sometimes. Unfortunately for tomato seed savers, a number of serious tomato diseases can indeed be carried on saved seed. The three general types of tomato diseases, caused by viral, bacterial, or fungal agents, are covered in detail in chapter 9. Even though fungal pathogens are the greatest in number, they tend to be more of a plant surface issue and, though they can be harbored on seed coats, are far less of an issue. Bacteria and viruses are better able to navigate the vascular system of the plant and wind up in the seed embryo, and hence the final seeds. Simple seed treatments can be used to minimize the pass-along disease potential from infected seeds. Of course, the best prevention is to ensure seed is saved from healthy plants only.
If I save seeds from hybrid tomatoes, will they germinate?
Yes. Any properly saved tomato seed will germinate, whether saved from open-pollinated or hybrid varieties. So it is not if you get a tomato plant; it becomes all about what you get. The F2 generation, which is what you are working with if you plant such seeds, will segregate into plants that genetically express the parents of the hybrid, depending on which characteristics are dominant or recessive. In summary, all bets are off when you grow tomato plants from seeds saved from hybrids. You may like what you find . . . and you may not!
Do I need to plant at least two of each type of tomato so that they cross-pollinate and produce tomatoes?
No. I am asked this question often during seedling sales by gardeners with limited space. They want to try out as many varieties as possible but think that two of each is needed to get a decent crop. Fortunately for the intrepid tomato explorer, tomato flowers are “perfect,” meaning that they effectively pollinate themselves upon opening. If you have room for 12 tomato plants in your garden, and you love variety, select 12 different tomato varieties and enjoy the experience of discovery as you learn about each of them.
Is it true that pink or yellow varieties are less acidic than red varieties?
No. According to a study carried out by the USDA in 1977, just about all tomatoes are similarly acidic.
Relative acidity is measured on a pH scale of 0 to 14, with 0 being extremely acidic and 14 being extremely alkaline. Acidity and sweetness are not opposites, however. In fact, honey (with a pH of around 3.8) is actually more acidic than tomatoes (which have a pH range of 4–4.6). Some tomatoes taste sweeter than others simply because their sugar content is higher, which masks the acidity.
When considering which tomato varieties to can, feel free to choose anything that is in good edible ripe condition. Acidity does drop off a bit with age, so very ripe tomatoes, which often taste unpleasantly sweet, are likely have elevated pH levels and are best kept out of the canning mix; sauce may be the perfect use for those that have been neglected on the counter or vine just a bit too long.
If I grow a tomato variety for enough years in my garden, and I save seeds each year, will it become genetically more adapted to my climate over the years?
No. A particular tomato variety has a specific set of genes that control how it grows, how it looks, and how it tastes. If, over a period of time, the tomato seems to change and adapt, it is likely due to either subtle changes in how it is grown, how the weather affects its growth, or even an inadvertent selection for different characteristics by the seed saver. For example, if half a dozen plants of a particular variety are grown each season and one plant does slightly better, and the variety is carried on by saving seeds from tomatoes only from the superior plant, something is likely genetically different about that plant. So, in this case, it isn’t that the genes are changing or adapting. Rather, a genetically slightly different tomato was found and is now the basis for refinement into a new variety.
