tomato-growing faq’s

Homegrown heirloom tomatoes

Q. What is the difference between a determinate and an indeterminate tomato?
Q. Should I grow heirloom or hybrid tomatoes?
Q. How much sun do I need to grow tomatoes?
Q. How do I prepare the soil for tomato plants?
Q. Do I need to plant my tomatoes in a different place each year?
Q. Can I grow tomatoes upside-down in one of those new hanging planters I saw?
Q. How and when do I start tomatoes from seed?
Q. When do I transplant my tomato seedlings into the garden?
Q. Can tomato seed be direct-sown in the garden?
Q. If I am buying tomato transplants, are big ones better?
Q. How do I plant tomatoes?
Q. Do I mulch my tomato plants?
Q. Should I cage, stake or trellis my tomato plants?
Q. Do tomato plants need pruning?
Q. When and how much do I water tomato plants?
Q. Do tomatoes need to be fed; I have read that they are “heavy feeders”?

Q. What is the difference between a determinate and an indeterminate tomato?

A. The terms refer to the growth habit of a particular variety (and there are also semi-determinates). Think of determinate and indeterminate like bush types and vine types.

Some varieties grow to about 3 feet and then stop, making them ideal for gardens with restricted space or container use. These are the determinates. Indeterminates, which includes many of the heirloom types, grow like the vines they are, as long as the season will allow.

Another difference is that generally speaking the relatively short branches of determinate plants end in a flower cluster, and most of these ripen in the same several-week-long period (a good trait if you want to make one giant harvest into quarts of sauce, for instance). With indeterminates, more potential flower-cluster-bearing growth is produced as long as conditions allow, so there are multiple harvests over a longer season.
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Q. Should I grow heirloom or hybrid tomatoes?

A. I grow a mix of heirlooms and hybrids for a little insurance: The non-hybrid, or open-pollinated heirloom types are beautiful, delicious and a critical part of our genetic heritage, but some may they lack the disease-resistance (often labeled VFN) of hybrids. I like to mix it up, though my sentimental preference is for the heirlooms.

Remember that even with hybrids rated as having VFN resistance, the word “resistance” is the operative phrase. It means less-susceptible, not immune. There is no substitute for good cultural practices, whatever variety you begin with (more on that below, in the bulleted list in the question about crop rotation).

Some commercial growers, especially of greenhouse tomatoes, have been adding a layer of insurance to their heirloom plants by growing them grafted onto more vigorous rootstock. More about tomato grafting is here.
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Q. How much sun do I need to grow tomatoes?

A. Tomatoes want full sun; don’t plan to plant them in a shady spot or they will languish. Sun means 7 hours of direct exposure, not a passing ray or two. If you don’t have an in-ground spot with that kind of sun, consider whiskey-barrel sized planters positioned in a sunny spot as an alternative—there may be a place for such an impromptu tomato patch somewhere in your yard, driveway, etc.
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Q. How do I prepare the soil for tomato plants?

A. Start with a soil test, or at least a simple pH test. Tomatoes like a pH of about 6.5 (6.0-6.5 or so is fine). In acidic soils like mine, the addition of lime is recommended, at the rate of 5-10 pounds per 100 square feet worked into the top 6 or so inches.

High-quality finished compost is the best amendment you can add to support great tomatoes. Work in a 2-to-3-inch layer each year. Some growers add more alongside the plants as the season advances.

An all-natural organic fertilizer that’s balanced or has a slightly higher middle number (Phosphorus) can also be incorporated according to package directions. Do not use a high-Nitrogen fertilizer or you will get foliage but not fruit. Also: Overfertilized, too-fast-growing plants are a target for trouble, and more inviting to disease; don’t overfeed.
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Q. Do I need to plant my tomatoes in a different place each year?

A. Alternating where you grow something is called crop rotation. Conventional widsom said to Identify a full-sun spot outdoors where your tomatoes will grow. Then pick another such spot, and preferably a third, as a three-year rotation is thought to provide defense against various tomato diseases that can overwinter in the soil. The thinking is also that no other Solanaceous cousins, no potatoes, eggplants, peppers or tomatillos, can go there in the off years, either.

I am only able to rotate every other year here, so I add lots of compost to the soil and follow these key steps recommended by tomato breeder and seed farmer Tom Stearns of High Mowing Organic Seeds, who says rotation doesn’t cut it:

Certain fungal pathogens, such as septoria and early blight, reside in the soils of the Northeast, mid-Atlantic and upper Midwest in particular, Stearns explained to me (listen to our archived podcast on the subject–it’s the second half of this show). That means that no matter how much you move your tomatoes around year to year–how much you rotate your crop–you can’t completely avoid these troubles.

“Rotating where you grow your tomatoes is not really going to help—so you must manage the disease,” says Stearns. What he calls “good tomato hygiene” starts with wide spacing, pruning and staking–all aimed at good air circulation. Tom’s tips:

  • Growing tomatoes on black plastic landscape fabric increases soil heat, provides weed control and help with soil-splash control–keeping some of those soil-borne spores from getting up onto the plant by creating a barrier.
  • Strip the lower leaves from the plants to eliminate the “ladder” for spores splashing up from the soil as well.
  • Trellis and stake tomatoes, and prune them to get rid of suckers. (From “Fine Gardening” magazine, details on tomato pruning.)
  • Focus on air circulation this way, too: Place tomatoes on the edge of a bed, not the middle, and never do a teepee or other too-close tangle of tomatoes.
  • With staked tomatoes, 18 inches between plants within a row is a good distance. Leave at least 3 feet between rows.
  • Overfertilized, too-fast-growing plants are a target for trouble, and more inviting to disease; don’t overfeed.

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Q. Can I grow tomatoes upside-down in one of those new hanging planters I saw?

A. Please, don’t grow your tomatoes upside-down, as is the fashion started by at least one recent gimmick product. Yes, they’ll grow if you follow the instructions, but why would you bother, why spend the money? The tomato experts at Rutgers agree with me on this one, by the way. I think there’s enough upside-down in the world without us adding to the dizzying picture, no?
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Q. How and when do I start tomatoes from seed?

  • Count back from 5 or 6 to as much as 8 weeks. Everyone has their own beliefs on this. I like a strong little plant grown in a medium-large cell, so 6 is plenty; my seedlings would need larger quarters (like a 3-or 4-inch pot each) to thrive for 8 weeks indoors; more work, but to my mind, no extra benefit.
  • Seeds germinated on a heat mat in flats will get off to a particularly fast start. A soil temperature of 70 degrees is essential; higher (like mid-80s) is better in those early days.  I do not use a heat mat when I sow directly in insulated, self-watering foam trays that last many years, rather than typical cellpacks and flats. If you use a mat, remove it once seeds germinate; heat mats are for germinating, specifically.
  • If you’re re-using seedling flats or other containers, clean with a 1:10 bleach:water solution or hot, soapy water.
  • Start with fresh seed-starting mix. A soilless mix (they are usually peat-based) is best. This is not heavier “potting soil,” but labeled for germinating specifically.
  • My long-ago hero, James Underwood Crockett of the original “Victory Garden” series, would sprinkle 6-8 seeds per 3-inch seedling pot, then after about two weeks, or when the plants were 1½ inches high, transplant them into 6-packs, one plant per cell. Confession: Rather than transplant, I usually put two seeds per cell and use a nail scissors to cut out the weakling, skipping the potting up. I start with slightly larger cells than a conventional plastic 6-pack, however; others swear by transplanting each baby to its own 3- or even 4-inch pot.
  • Barely cover seeds after sowing with ¼ inch more mix and tamp down, then moisten thoroughly (easiest with a spray bottle). If you are using a bottom-watering system like APS, mist the tops, then fill the water wells.
  • Keep the covered trays in a warm spot (no light needed or even desired). Again, 70 degrees is the minimum requirement, and the desired temperature throughout their young lives.
  • Do not let the seeds dry out before they germinate.
  • Germination will take place from a few days (with early varieties) to 10 days or so. A consistently moist environment is essential, but don’t let them cook or drown, either; vent the lid or bag so no moisture beads are ever running down the sides. Remember: when the seedlings show, remove the heat mat.
  • Once up, it’s critical to move the babies fast to a high-light situation or they will stretch out and be useless. Forget low light, such as a windowsill. You want 12 hours of strong light minimum a day; some think 14 or 16 is better, with the lights close to the plants (a couple of inches, meaning some form of adjustable setup is required. I recently got a new adjustable light set-up, which is detailed here. On warmish days, I bring my plants outside into a protected, bright spot to give them even more light (more on why I do that is here). No artificial light source can do the seedling-strengthening job that sunlight can!
  • Feed with half-strength water-soluble fertilizer after the first true leaves appear. Important: If the seed-starting mix you bought includes fertilizer, go easy or skip this step. Overfertilized baby plants can stress out and even die. If using unfertilized mix, plan to feed at half-strength twice during the plants’ indoor growing period.
  • They will grow fast now, and this is when you must transplant if you sowed in “community pots” or they’ll become overcrowded.
  • Don’t water with cold water; and never douse. Mist, with tepid water, or use a device whose spout delivers gently. One system I use has wick-like felt mats beneath the cells that draw up moisture, so I just need to get things started and supplement occasionally with my spray bottle.
  • Turn on the fan, on low, not right next to the plants but so they feel it a little bit. This helps strengthen them, like young trees whose trunks grow stronger in the wind. Air movement also helps prevent deadly fungal diseases like damping off.
  • Brush the tops of the seedlings daily with your hand to provide the “mechanical conditioning” that creates sturdy, not spindly seedlings. Not just once, but gently for a half-minute or minute. (Yes, go ahead, talk to them while you do it. I probably do without even realizing it.)
  • If any flower buds form on your young plants, pinch them off. Don’t let the baby stress itself trying to reproduce just yet.

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Q. When do I transplant my tomato seedlings into the garden?

A. After all danger of frost is past, it’s planting time. Hurrying doesn’t help, and it can hurt; I usually wait until a week after my final frost date. Even if you plan to offer protection from devices like plastic-wrapped cages (clothespins work well to hold the plastic in place) or walls-o-water or hotcaps, I have never found that really pushing it does much but add to my workload. Time the babies to go out when it’s safe, and not before.

Harden off your transplants over the last week in your indoor care with daily trips outside to enjoy a taste of what’s to come, returning them to a protected place at night.

Follow the bulleted steps in the crop-rotation question above (laying down black plastic, pruning off lower leaves, etc.). On transplanting, snip off any flowerbuds that set until the plant is settled in and growing strong, after it reaches perhaps a foot tall or so.
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Q. Can tomato seed be direct-sown in the garden?

A. If the indoor seed route sounds daunting, you can direct-sow tomato seed right in the garden if your season is 4 months or longer between frosts…and if you are vigilant about weeding and. It can be hard to keep a tiny emerging seedling happy in the outdoor environment; vigilance will be required.
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Q. If I am buying tomato transplants, are big ones better?

A. The garden center can be a confusing place, and prices can vary from less that $2 for a 6-pack of something to many more dollars for a single large plant. I say buy smaller, but select ones that are stocky and tough. Start with dark green, stout transplants equally high and wide, preferably about 4 inches in each direction.  (My step-by-step for growing your own includes many tricks; you can also shop locally for seedlings or by mail.)
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Q. How do I plant tomatoes?

A. Plant deep, at least to the level of the original seed leaves, or even to the topmost couple of pairs of leaves. (More on how, and how deep, here.) Water in well, applying first of two doses of liquid feed; see below under “Douse each plant’s root zone,” for details.

Space plants at least 2 feet apart in each direction; 3 or more would be much better, as air circulation is another disease-preventive tactic. Caged plants need wider spacing than staked ones, and indeterminate varieties more than some determinate; plan accordingly.

Follow the detailed instructions in the bulleted list above, in the question about tomato crop rotation, pruning off lowest leaves, laying down black plastic and so on, to help manage disease.
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Q. Do I mulch my tomato plants?

High-quality woven polypropylene landscape fabric, such as is used on greenhouse floors, is an excellent, porous, weed-preventive measure for a tomato patch. It can be reused for many years. Staple it to the ground with earth staples. On top of that, a layer of clean straw or some other organic mulch will further reduce splashing of spores and other woes up from the soil onto the plants.

Just have a few plants or a single row and the fabric would be overkill? The straw or equivalent alone will suffice.
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Q. Should I cage, stake or trellis my tomato plants?

A. I recommend that you decide on one of these methods to support the plants, to keep them up off the ground, for best health. There and pros and cons to each style.

  • Staked plants will ripen faster crops of generally larger fruit. Staking and pruning also helps manage disease. Stakes must be at least 1 inch thick and 6 feet high, inserted a foot into the ground.  Remember: Staked plants require a commitment to ongoing pruning, keeping the plant to one or two main stems of vine-like, not bush, habit. All small suckers that develop in the crotches between the leaves and the main stem must be removed. Here’s the encyclopedia of tomato-pruning if you wish to stake (or trellis) and prune.
  • Caged plants are easier to care for, and in the longterm may produce heavier yields (because they have more branches and stems). I bought a set of cages that also fold; you can make excellent cages from concrete reinforcing wire (6 feet of it makes a 22-inch cage). Stabilize each cage with a stake and twist-ties, unless the cage has inground legs.
  • Another advantage of cages: You can use them as mini-greenhouses should late or early frosts come, by having clamps and reusable pieces of clear, heavy plastic cut to wrap each cage. Some expert growers always put the plastic on in the first weeks to reduce negative effects of wind on young plants.

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Q. Do tomato plants need pruning?

A. Staked plants do need pruning (as above); a good reference on tomato-pruning is here. Some gardeners who do not stake prune anyway.

Though this is more pinching than pruning, snip off any flowerbuds that set until the plant is settled in and growing strong, after it reaches perhaps a foot tall or so.
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Q. When and how much do I water tomato plants?

A. Tomatoes rely on you to team up with the heavens and provide consistent moisture, consistent being key. Ideal is the equivalent of an inch of water throughout the entire growing area; half again as much in the heat of summer. Remember: an inch of rain (which is what you are simulating) is a lot of rain, and takes a long time to apply. Use soaker hoses or a drip system, not the end of a hose. If you must use a sprinkler, use it in the morning, so that foliage can dry by day, and don’t work in the garden while the foliage is damp.
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Q. Do tomatoes need to be fed; I have read that they are “heavy feeders”?

A. Douse each plant’s root zone with a liquid feed twice during the growing season. Some growers swear by doing this at transplant time and again when the first flowers appear; others say transplant and first fruit. Just remember to do it while they are in their run-up to adulthood and you will be fine. Powdered seaweed fertilizer or fish emulsion diluted in water according to label directions are two non-chemical possibilities, and compost (though not technically a fertilizer) is always welcome.
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For a detailed FAQ about tomato troubles–preventing, diagnosing and fighting pests and diseases, click here.

21 comments
April 14, 2010

comments

  1. says

    I was hoping you’d have an answer about those upside down planters. My mom bought two of them for us last year. (Actually, I think she bought them for herself and decided she’d never use them.) I was excited about using them because I’ve run out of space in the raised beds my husband made for me. Then someone from work told me she tried them two years in a row and didn’t have any success with them. Do the things just not work well usually? Is it even worth trying since I already have them?

  2. says

    Well put! I’d be writing a post on the same topic but since you’ve got it covered I’ll just share this around. And I agree about our upside down world (and tomatoes). I’ve got a similar feeling about those “potato bags” being sold now. Have you seen those?

    Since our soil was too muddy for transplanting, we’ve been potting up our seedlings to buy time until they can go in the ground. We made a little how-to video (plus you get a peek at the Seed Library farm). Hopefully you’ll be able to come visit us when we dry out a bit. But for now here’s a soggy snapshot of the seed farm and hoop house: http://www.seedlibrary.org/wp/?p=1657 .

  3. Sarah says

    This was some great information. Thanks!

    Have you tried the new spiral stakes? My tomatoes absolutely love them, I don’t have to physically tie them to the stakes, and they don’t need to be pruned. Even better, the stakes are only about 1/4″ in diameter.

    • says

      Hi, Sarah. I have not tried the spiral stakes. Will look at them, thank you. As for rotating tomatoes, I have to say that I feel as if in my raised beds (even though I add compost etc. each year) there has been some carryover sometimes from year to year of problems. I’d love not to rotate them, so I will read up on Coleman’s advice and see what else he is doing that might be helping.

  4. Sarah says

    I meant to also add that Elliot Coleman claims tomatoes actually grow better if they are planted in the same spot year after year instead of using a normal crop rotation. If there is a disease issue, though, he highly suggests rotating them to a non-infected plot. Have you played with this at all? I haven’t moved my tomatoes in three years, and they do seem to get bigger each year, but I might also have just gotten lucky with the disease/pest issue.

  5. Pam Oleary says

    Tried the topsy turvy tomato planters and they didn’t grow or produce any fruit. Waste of money. Grew tomatos in stacked tires and had abundant harvest.then tried growing tomatos in square foot garedning grow box.they didnt grow at much either and did not produce any fruit.this year I will dig through the landscape material under the soil to give them more root space. Hope that works. ( Had to get rid of tires.they didnt look nice.My back yard is open and I had to clean up . May buy a few tomato grow bags. Has anyone used them?

    • says

      Hi, Pam. I have not — generally speaking, I am old-fashioned and skip the gimmicky stuff. I am thinking of trying to find some cheap used whiskey barrels for tomatoes, actually, at the moment. Hope I come across some…

  6. Rae says

    I live in a condo, have added a 4×4 raised bed in the cul-de-sac and planted two tomatoes as last year. I had success, but think I need to fertilize more. Trying a new variety of tomato in a large pot, ‘Tomaccio’ which are supposed to dry like little raisins. We’ll see how that goes.

    • says

      Hi, Jeff. Have you been feeding a lot perhaps? They like nutrients but not tons of Nitrogen, which will produce more plant than bloom. Other nutrient issues can affect flowering as well. Also if the plants are in a semi-shady spot, that can limit the inclination to bloom. Or are the blooms forming and falling off, which can happen in high heat, for example?

  7. theresa says

    I have a concern regarding spots ,which I think is a bacteria problem ? Do I just take the plant out and next year start over or use a bonide product to try and salvage it ?

    • says

      Hi, Theresa. With fungal things, I think they are more easily prevented than cured (though not easy in certain years to prevent, either!), so no, I don’t try to do anything, except try to nurse along any possible fruit. If it were late blight, yes, I would remove and destroy all the plant parts. Important to try to find out what it was — your local cooperative extension can guide you to a diagnosis, I expect.

  8. carolyn says

    thanks so much for the great info. i have actually grown tomatoes from seed in a galvanized bucket and produced some fruit. Not sure what kind of tomato it was as it came in a plastic egg and did not say. But, since it was my first attempt at growing tomatoes, i was happy anything grew.

  9. Betty Frost says

    This is the first time I have planted tomato seeds and I appreciate what I have read on your site. I am planting black cherry tomatoes and am hopeful some of the seeds actually turn into plants with lots of tomatoes. I will be planting them in planters on my patio. What type of soil should I buy for the pots? I am not a gardener, so this is a big step for me.

    • says

      Hi, Betty. In pots, we can’t really use real soil, as in the ground, but rather a potting mix that’s actually “soilless” and made of peat and ground bark and so on. I like to buy one that is “bark-based” (meaning a little heavier weight than the ones that are mostly peat moss) and I buy the ones without chemical fertilizers added. I sometimes mix compost (you can buy it bagged if needed) with the potting soil. Ask at the local garden center for advice which products, since each region has different brands. In the Northeast I use one by Fafard called Fafard 52 mix and add compost, too, but that’s not sold nationwide (an equivalent kind will be).

  10. Sarah Sellers says

    HI Margaret-
    I have 18 beautiful tomato plants in a 4×12 raised bed. Yes, it looks like Jurassic tomato park, lovely, but probably not best situation to yield, pest control, sun, feeding, watering, etc. Could I move some of them now to a similar soil in neighboring bed?
    I started these babes from seed and am very attached to them.
    Best,
    Sarah
    Sharon, CT
    Zone5B

    • says

      Hi Sarah. Yes, you can transplant if you must — but of course if they are big and gangly it’s a bit of a challenge! If they were staked and pruned like this, they’d almost fit there — but again, you’d be late to the starting gate for that, I fear. I assume they are in cages maybe? How tall?

  11. Geno says

    Hi Margaret I like all your information. Have a question on a ant infestation on the roots of a tomato. I was told it was do to a parasite attracting the ants. Is that true and how does one get rid of them?

    • says

      Hi, Geno. Usually ants are not looking to eat a plant, as much as being attracted by something else, I believe — for instance, by the sticky secretion made by aphids, called honeydew. I do know that aphids can be parasitized by wasps (like this) but as for ants on the roots of a tomato specifically, and so on, I don’t think it’s about the tomato specifically. I would be inclined to use water to try to dislodge/discourage them and also check the plant carefully for signs of aphid infestation or honeydew.

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