5 Secrets to Grow Tomatoes: 100 lbs in 20 Square Feet

5 expert secrets on how to grow 100 lbs of tomatoes in 20 square feet. Lots of vegetable gardening tips on soil, care, trellis ideas & more!

Last year, inspired by some amazing organic gardens we visited,  we experimented with new ways to grow tomatoes.

Our tomato plants were more vigorous and healthier than they have ever been!

In a 20 square foot area, we harvested over 100 lbs of delicious tomatoes from just six “Early Girl” tomato plants , a popular variety that can be easily found in most nurseries.

5 proven secrets we learned from experts on how to grow tomatoes & harvest over 100 lbs in 20 square feet! Lots of care tips on soil & free trellis plan!

Today I am excited to share with you the tips and tricks we learned on how to grow tomatoes like an expert and get a huge harvest!

*Some resources in article are affiliate links. Full disclosure here.

Tips number 1, 3 and 4 are something new we tried that made all the difference!

Before we go into details of the tomato growing techniques, these are a few basics that apply to all vegetable gardening: plenty of sun, good soil, and productive varieties that are suited for your climate.

The easiest way to build great soil on any site is to create a simple raised bed. Here are lots of tips and tutorials on DIY raised bed gardening-

All About Raised Beds: Ultimate guide on how to build the most productive raised bed gardens! Lots of tips and resources! - A Piece Of Rainbow

All about DIY raised beds.

Tomatoes come in determinate and indeterminate varieties, which is written on the plant label.

Determinate tomato varieties are small compact growers with a short harvest season, they are great for small space gardens, pots and containers. Our tips 3 and 4 will not apply to these.

DIY tall tomato cage trellis

Most of the great tasting and heirloom tomatoes (for example- “Early Girl”, “Cherokee Purple”, “Sweet 100“, “Brandywine”) are indeterminate tomatoes, which means they continue to grow and produce tomatoes all along the stems throughout the growing season. These are the tomatoes we prefer to grow.

big tall tomato plants growing on a garden trellis

Grow Tomatoes Secret 1 : Tomatoes love warm soil temperature and lots of direct sunlight.

“The earlier we plant, the sooner we get our first tomato, right? ” Actually, no. Tomatoes should not be planted outdoors until after the average last frost date for your area, although you can start seeds indoors 6-8 weeks before the last frost date.

Tomatoes hate cool soil temperatures. The ideal soil temperatures to grow tomatoes are between 70 – 90 degrees Fahrenheit. Tomato plants love full sun locations with at least eight hours of direct sunlight a day for healthy growth and fruit production.

Temperatures dipping below 55 degrees Fahrenheit stops plant growth. The less active the growth cycle, the more likely the plants will have insect and disease problems such as blossom end rot, early blight, etc.

grow tomatoes tip 1: black plastic to heat soil for tomato plants

In most places, the night time temperatures can be quite cold in March, April, or even May. To solve this problem, we used the dark plastic mulch method which we learned from amazing gardeners who grow tomatoes successfully even in challenging climates.

Open up a few black plastic trash bags, lay them on top of the soil,  secure along the edges with wood planks or rocks. Cut 3″ to 4″ diameter holes for the transplants. We planted our tomatoes on a 30″x30″ grid.

Our black plastic trash bags worked great!  You can also buy plastic mulch for tomatoes such as these.

plant tomato seedlings under plastic mulch

The plastic was able to raise the soil temperature by 10 – 20 degrees Fahrenheit during the day, and hold the heat better at night, which was perfect for most spring days and nights when temperatures are between 45 – 65 degrees.

As the weather gets warmer by summer, the plants will have enough leaves to shade the plastic and prevent it from getting too hot. We could tell how happy the plants were. In a couple of weeks, the seedlings were growing rapidly and looking super healthy!

Another benefit: When soil moisture level fluctuate too much due to weather and uneven watering, tomato plants can drop blossoms, or develop blossom end rot. This black plastic mulch is great for keeping a good soil moisture level.

Grow Tomatoes Secret 2 : Plant deep in compost rich soil

Compost is rich in nutrients for healthy and faster plant growth, it also promotes soil microbes which aid plant growth, and improves soil structure in sandy or clay soil so the soil can better retain water and nutrients.

Here are 25 best DIY compost bin ideas.

We have compost rich soil, and we don’t even fertilize our tomatoes. However, if you want to add additional fertilizer, choose an organic fertilizer with an NPK ratio that is higher on the P number. NPK stands for nitrogen ( for foliage growth ), phosphorus( for fruit production) and potassium( for healthy roots). This Dr. Earth 4-6-3 tomato fertilizer is a great choice.

Is manure a good fertilizer for tomatoes? Manure contains too much nitrogen, which is good for foliage growth when plants are small, but not very helpful for flowering and fruiting as the plant grow.

Prune off the bottom leaves and  plant about 2/3 of the plant underground.

How to root tomato cuttings in just one week! Now you can multiply lots of tomato plants quickly and for free! | A Piece Of Rainbow

Because tomato stems grow roots easily, we can propagate new ( and free!) plants in just a week from stem cuttings of a big plant! Tutorial here-

Tomato plants have this amazing ability to grow roots along the buried stems, which will make the plants stronger.

Secret 3 : Prune tomato plants fearlessly.

Have you grown a huge tomato plant, only to get a ton of leaves and very few fruits? Then it just wilts and dies?

The best solution is to prune tomato plants regularly. Pruned plants allow more sun light to come through and more air flow. The leaves dry faster after a rain, so they are less susceptible to the diseases such as blights.

where and how to prune tomato plants

The orange arrow indicates the main stem, and the blue arrows indicate the side shoots / suckers which can grow into a stem. The goal is to leave only 1 or 2 stems growing ( some say up to 4 stems ), and prune off all the suckers.

It is very easy to miss one until it has grown too big. So do this at least twice a week, and be ruthless!

grow tomatoes with thick healthy stem 1 inch thick

 See how thick and healthy this main stem is? Instead of growing 50 to 100 stems, the plant is able to concentrate it energy on the main stem and keep producing fruits. ( This method is suited to indeterminate tomatoes which we talked about at the beginning.)

Secret 4 : Grow tomatoes vertically to improve air circulation and maximize sunlight.

DIY tomato trellis support with wood

You can grow healthy tomato plants using a DIY trellis. The other new thing we did which made a huge difference is to build a tall trellis and tie strings between the top and bottom rail to wrap the tomato vines around as they grow.

You can adjust the tomato trellis height to 4 to 5 feet tall, especially for smaller tomatoes such as cherry tomatoes and plum tomatoes.

how to build a  tomato trellis , free plan

We made our tomato trellis from pallets, using 2x4s as the main X frame and 1x4s to join them together. Here are tips on where to find and how to take apart pallets!

All about pallets.

As mentioned in tip #3 we prune each plant to keep only two stems growing. Each stem wraps around a string, keeping good air circulation and making any pruning and harvesting super easy.

strings on DIY tomato trellis, works better than tomato cages

We used thin jute twine but they deteriorated toward the end of the season. We will use heavy duty garden twine in future. ( This method is suited to indeterminate tomato plants which we talked about at the beginning.)

You can also use other trellises. Check out these 24 best DIY garden trellis ideas.

Secret 5 : Keep tomato plants dry.

Gardeners who grow tomatoes know how quickly disease such as blights can make the foliage turn dark and brittle, and kill the tomato plants. To prevent early and late blight, water the plants at soil level and keep soil or water from getting onto the leaves.

diy tall tomato cage for growing vertical

It is easy to water under the plastic mulch: just insert a hose from one end, or install a soaker hose before laying down the plastic.

We planted these tomatoes in early May. Believe it or not, our coastal San Diego weather is not the best for growing tomatoes.

ripe tomatoes in garden

Because of these new methods we tried, we were able to get a much bigger harvest than ever in not-so-ideal conditions.

Between July and early September, we harvested over 100 lbs of tomatoes, usually around ten tomatoes at a time.

healthy tomato plants under a diy trellis

We did let some plants grow to 5 stems which lead to disease build up at the end. I think by keeping the plants better pruned we can actually grow over 200 lbs in 20 square feet!

You may also love: DIY strawberry tower with built-in reservoir!

DIY Strawberry Tower with reservoir! | A Piece Of Rainbow Blog

Here are a few additional resources on growing tomatoes you may like to explore:

Bonnie Plants guide to growing tomatoes in different climates, the Almanac’s guide on planting and harvesting tomatoes, how to build sturdy tomato cages via instructables, one of our favorite tomato seed source Baker Creek, and our collection ofΒ 35 creative DIY container veggie garden ideas!

Happy growing! See you soon!


  1. Wowza! Your post renewed my hope to grow tomatoes successfully in the cool coastal conditions of San Diego:-) I have used all the strategies you discuss, except black plastic–and I bet that is the key! Especially love that you included a visual for May Gray and June Gloom πŸ˜‰ It’s no joke that our spring weather is cool and overcast! I wonder if it has helped at all to plant REALLY early? Give the plants a headstart before May Gray? Appreciate your website! Thank you:-)

    • hi Gene! so sorry for the very late reply, we lost some comments due to spam bots! we find that starting too early doesn’t help. in fact, this year we will plant 1/2 of our tomatoes in march, and 1/2 in late June to take advantage of the hot September weather. will update here! and yes black plastic is super important for coastal climate! πŸ™‚

    • Black trash bags contain high levels of lead and cadmium during production that can be harmful to human health, which can directly affect the brain and lungs. Plastic garbage bags are NOT food-safe and may have been treated with scents, deodorants, or other compounds meant to reduce odors and discourage pests. Trash bags are made from polyethylene β€” a flexible, tough, light plastic that is mainly used in packaging, containers, and insulation. Polyethylene is a polymer of ethylene, which is a colorless gas used in the manufacturing of several chemicals. In addition, the composition of formaldehyde or tributylin in the paint used to print words on garbage bags is dangerous to human health. These substances can penetrate the skin, leading to the risk of dangerous disease. Although using them improved your tomato production, you have sacrificed the safety of the food. It would be wise not to encourage others to use them in the manner that you have suggested.

  2. Nice article but ” Early girl” tomatoes are not a heirloom variety πŸ™
    They are F-1 ( first generation) hybrid of 2 different parent plants which means it’s seeds aren’t true. Since 2005 Monsanto purchased the seed paten ” Early girl” and is now the primary producer of ” Early girl” seeds!! So I’d personally avoid ” Early girl ” tom’s .

  3. Excellent advice for tomatoes. I garden in the mid Atlantic and would add soil conditioning and regular feeding as 2 related keys to realizing maximum yields. What puzzles me is your choice of the early girl. We grow a few of these every year along with another early tomato “4th of July”. I find the latter a better choice for taste,yield, and shorter time to first harvest. But I have never found an early variety that I consider a high yield tomato. If high yield is what your striving for I would suggest a brandywine variety.

    • thank you John for sharing your ideas! πŸ™‚ early girl has been a good choice because it always keeps producing over a long season vs brandywine types tend to give us a few huge tomatoes, then stop growing. but as with everything gardening, it could be so many reasons, one being that we are near the coast with June gloom! πŸ™‚

  4. The part where it says to prune and then plant about 2/3 underground- I’m confused! Do you take the plant out and just dig a bigger hole to put it in or just build the soil up around it? I love all the tips in here and am excited to try them this season!!

  5. Pro tip: sow basil at the base of the tomato as a “sacrifice” companion. Most insects will be attracted to the basil and will leave tomatoes alone and it’s also a strong mosquito repellent

  6. Thanks for the info!!! Fantastic article! One question though….how does one piece of garden twine support the whole plant? Do you have more detailed pictures of this? I just cant imagine them being supported by one piece of twine for each plant! thanks so much for the info!!

    • hi erin, the twine is pretty strong, and it guides the vines which grow super thick when they are pruned, so that helps too. we will add more detailed photos next season! πŸ™‚

  7. Ooops,i forgot something,you said we could build this trellis with pallet wood,but I’m confused,are the pallets where you are a LOT bigger than ones used here in MA ??? Because the lengths on the diagram for the trellis are much too long for the reg store pallets we get here πŸ™
    Thank you !!

  8. I loved this article! I am getting ready to plant my first garden this year and want to be successful with tomatoes as I’ve never had much success. Your post is very informative, however I am still unsure about the pruning method. Do you have another post about this in more detail, or have any further tips?
    Thanks again for taking the time to write this!

  9. I did not know that there is a way you could easily increase soil temperature to grow tomatoes more comfortably. In fact, I could not wait to try it out. It has been only a few days but I think it will bring a lot of positive changes to my garden, having had issues with cold weather in the past.

  10. Great article!

    I watered from below too this year, and it worked great! I “planted” homemade ollas for my tomatoes, planting my tomatoes in a triangle around each olla. I used two medium-sized terracotta pots for each, sealing the bottom hole of one with a broken tile and silicone aquarium sealant, then securing the pots rim to rim. Leave a couple of inches out of the soil, fill with water, and cover the hole with a big rock. I read about this method years ago and made the ollas, but they sat in a corner of the garage until I found them last spring! They worked great, and kept the plants going when we went on vacationβ€”no mean feat in Georgia’s hot summers!

    I’m going to take your advice and force myself to prune this year. I got a lot of smaller tomatoes this year; maybe I would get larger (if fewer) tomatoes if I pruned. Maybe I’ll prune half and see how it goes!

    Thanks for the inspriation!

  11. Great article. So do you NOT prune determination varieties? I bought some tomato plants at a farmers market and don’t know what type or variety they are. Is there a way to determine?

    • hi monica, i would google “(variety name) tomato is determinate or indeterminate” you can usually find seed companies with great descriptions =)
      the reason we don’t prune determinate ones is because they are already compact enough, but you can certainly cut off some side shoots to root new plants!

  12. We have raised beds in our garden but this year when I plant tomatoes I am going to plant the “Big Beef” variety in stacked used car tires. These monster tomatoes literally kill any regular tomato cage. I plan on staking them with rebar and then let them run over the sides of the tire beds. My plan is to stack them 3 tires high. will be using the newer tires with the narrow side walls. Any tire store will either give them away for free or charge a nominal fee for them. I am lucky, we sell tires.

  13. Great post !! Definitely bookmarking this one! My family’s retirement plan is to be self-sufficient on our land so i’ll definitely be sharing this one with them πŸ™‚

  14. This is SO helpful! We love growing tomatoes but have run into a couple of problem with our plants falling over due to the weight. Sounds like we need to be better at pruning and build a better support system to help them grow vertically. Thank you!

  15. My grandfather used to grow tons of tomatoes every summer. He was really good at it. I am not. I’ve tried to grow a couple plants, but they died. If I ever move out of my apartment, I’d love to have a small garden again. Your tips would come in so handy! Thanks for sharing. πŸ™‚

  16. I have tried and tried to grow tomatoes. One year they do wonderfully, the next year they do horribly. I am pinning this to read when it comes closer to planting season! Thank you for the wonderful advice.

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