How to Grow Tomatoes: The Ultimate Guide

How to Grow Tomatoes: The Ultimate Guide
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How to Grow Tomatoes: The Ultimate Guide

How to Grow Big, Tasty Tomatoes

You can sow tomato seeds directly into the warm spring soil when nighttime temperatures stay above 55 degrees F, but because tomato seeds are slow to sprout, most gardeners prefer to start them indoors in late winter. To decide when to start your seeds indoors, find out the latest expected frost date for your area (your County Extension Office can tell you when this is), count back 5 to 7 weeks, and that's your sow date!

Park's Bio Dome seed starter is a great way to sow tomato seeds, because each bio sponge has a pre-drilled hole you just drop one seed into -- no need to thin seedlings, no wasting of seeds! You can use either the original 60-cell dome or our 18-cell Jumbo dome, which grows big, stocky seedlings ready to transplant right into your garden.

Place your Bio Dome in a 70- to 75-degree room, or just use a seedling heat mat to raise the temperature in the dome. You should see the first sprouts in around 3 to 8 days. They won't look very promising -- they'll be bent over, as if you'd planted the seeds upside down. Don't worry though -- they're actually just unfolding their cotyledons. This pair of leaf-like things will eventually wither and drop off once the plant gets its true leaves.

As soon as your sprouts are up, place the seedlings under strong light. Fluorescent light for around 14 to 16 hours a day is ideal for fastest growth. Keep your seedlings just a few inches below the light so they don't "stretch" and get "leggy." If you don't have strong artificial light, a sunny window will work too -- just keep the clear dome on your Bio Dome to protect your seedlings from those chilly drafts! (And if your seedlings do stretch some -- get long stems with too much space between leaf sets -- don't worry! Tomato plants are very forgiving, and you'll fix this little problem when it's transplant time!)

Congratulations! Your Tomato crop is up! Now just keep an eye on that weather report . . .

When it comes to transplanting tomatoes, you want to ignore your calendar. Outdoor temperature is the most important factor in transplanting tomatoes; far more Tomato plants are killed by being put into soil that's too cold than from any pest or disease. Both the soil and the air temperatures needs to stay above 55 degrees Fahrenheit, even at night, before your plants are ready for transplant. When in doubt, just keep them inside a bit longer.

When the weather starts being cooperative, it's time to harden off your seedlings. This process will acclimatize your indoor plants to the outdoor world, and it usually takes around 5 to 10 days. Wait for a nice warm day and move the Bio Dome full of young plants to a sheltered spot outdoors -- one that's shady and protected from wind. Leave your plants out until evening, then bring them inside. Repeat this process until you get a very mild night; then leave your plants outside overnight. Soon your tomato plants should be spending all their time outside, and the'll be ready to be transplanted (unless the temperature drops steeply!).


Choose an overcast day or late afternoon to transplant your tomatoes to keep your plants from getting stressed by too much direct sunlight on their first day in the ground. Find a nice sunny spot and dig a hole about 18 inches wide and deep for each plant. If your seedlings have stretched, you'll want to dig it even wider. Work vegetable fertilizer into the hole, then mix one shovelful of compost or humus into the soil you'll be adding back.

Set each seedling into a hole so that it will be buried right up to the bottom leaf pair. If your plants have stretched, just remove the bottom few sets of leaves and place the plant horizontally in the hole so that only the top three sets of leaves are above ground. Either way, you should be burying some green stem. This might seem odd, but don't worry; tomato plants can root all along their stems, so the buried stem will soon be healthy roots! (It's the only vegetable plant I know of that can perform this trick!)

Press the soil down firmly around your freshly planted tomatoes, sink a pair of Tomato Boomers fertilizer spikes on either side, and water thoroughly. If you're growing an Indeterminate or ISI (vining) plant, go ahead and put your Tomato Pen or Tower in place now.

Tomato fruits are full of water, so of course these are thirsty, thirsty plants. Your tomato plants need about an inch and a half of water each week, which is around 50% more than most plants need! Test the moisture around your plants several times during the first few weeks after transplanting by sinking your index finger into the soil right beside your plant all the way to the knuckle. If your finger is at all dry, you need to water the plant more.

If water is scarce and you're worried about your Tomato plants getting enough, I strongly suggest you use an Automator. It fits easily right around the plant's stem, inside your Tomato Pen and funnels water and fertilizer right down to the plant roots, keeping the water where you need it rather than all over the place. It also keeps weeds down and prevents evaporation, saving you time and money.

Mulch your plants well right away, too. Your mulch can be something as simple as pine needles or even old newspaper, or something as sophisticated as our Red Mulch, a plastic sheeting that will actually increase the growth speed and strength of your Tomato plants. If you're using a biodegradable organic mulch, layer it on as thick as you want! It's great for your soil and will protect your plants from temperature changes, weeds, and even some evaporation.

Your tomato plants also need a lot of food to grow their best. Fortunately, this is easy and inexpensive to provide. That one dose of fertilizer you added to the soil when transplanting will last the entire season. Twice a month, you can toss in some seaweed, which is a growth enhancer (and which is 100% natural -- no potentially harmful chemicals to worry about, and it's completely safe around children, pets, and every other plant in the garden, which will love it!). This combination of a slow-release fertilizer, a liquid feed, and a seaweed growth enhancer is can't be beat!

Tomatoes prefer a deep, thorough soaking once or twice a week to lighter, more frequent watering. This encourages deep roots that grow down into the soil (where they can find other sources of water), so you can actually use less water with heavier, less frequent soakings.

Once you begin to see fruit, ease up on the watering. Your Tomatoes will be even tastier with a little less water.

Use color to determine when to harvest your tomatoes. When they're red (or pink, or yellow, depending on which variety you're growing!), they're ready to be picked -- don't wait and let them get soft. If you still have Tomatoes popping up when the first frost is threatening in autumn, pick them green and ripen them in a cool, dry place inside.

That's all there is to it! Just one more quick suggestion for a great crop: marigolds! These annual flowers are the Tomato's (and the Pepper's) best friend. Marigolds kill nematodes, soil-borne pests that can easily destroy an entire Pepper or Tomato crop in no time flat. Marigolds are easy to grow from seed -- just start them inside a week or two before starting the Tomato seeds. They also look gorgeous, and you can even eat them! One Marigold variety has been developed to fight nematodes better than any other, and it's been proven more effective than chemical pesticides -- which no gardener wants anywhere near our vegetable plants if we can help it!