Take-aways from a Tomato Tutorial

Why did the tomato go out with a prune?..... Because he couldn’t find a date!

Bad jokes aside, a group of community gardeners recently took some time to ketchup on tips for improving their tomato harvests, thanks to Northside garden mentor Sarah Johnson. Last month Sarah wrote a blog post to lay the groundwork for choosing and transplanting tomatoes (read it here), and last week she followed it up with a hands-on tomato workshop focused on tomato care throughout the growing season (bruschetta included).

Here are a few of my takeaways from the workshop. If you couldn’t make it last Tuesday but have a tomato-related question, feel free to email Sarah at sarah_nside@gardencityharvest.org, or leave a comment at the end of this blog post so we can all learn more.

The good news is that caring for tomato plants doesn’t have to be very complicated. In fact, if you just leave your tomato plants to grow on their own, you’re still likely to get a good harvest from them. However, if juicier, more flavorful tomatoes are what you’re after, there are three main things to do to keep your tomato plants healthy and happy: Support, Prune, Fertilize.


Caged tomato

Providing tomato plants with proper support helps keep the fruits off the ground so they are less likely to rot or get eaten by pests or become afflicted with some disease. The best support structure to use depends on if your plant is determinate (more bush-like, grows to a certain size and fruits pretty much at once) or indeterminate (continues to grow new vines and will fruit throughout the season).

Since determinate plants only grow to a certain size, they do best when caged or staked and tied. Determinate plants do not need to be pruned, so cages work well because they are simple and you only have to worry about being able to pick the tomatoes.

Determinate plants do best when staked or trellised. These methods allow you to more easily access the whole tomato plant when pruning.

Staked tomatoes





If left to their own devices, indeterminate tomato plants will continue to grow and grow, putting lots of energy into more and more vines (also known as suckers). We prune these suckers so that the plant focuses its energy on growing bigger, more delicious fruits instead of more vines. The suckers, although they look small to start, will eventually grow into a whole new vine that will flower and set fruit, so it’s best to get them early.

Photo from Sarah Johnson

I imagine that writing about how to prune tomatoes won’t be very effective. Here’s a short youTube video that demonstrates the basics about pruning tomatoes.

Other tips on pruning:

  • Start pruning relatively early (about when the tomato plant has three suckers beginning to grow), then try to continually prune about once a week or so to keep up with the plant’s growth
  • The verdict is still out about what is the best number of vines to allow your tomato plant to grow. Both Sarah and I have found the general consensus among area farmers to be 3-4 vines per plant; 4-6 vines for a cherry tomato plant. Once you’ve picked the chosen ones (those few vines that look the strongest and will be allowed to continue growing) trellis or stake them so they are easily identifiable. This will make future pruning much easier and will allow you to train the vine around the string it’s tied to as it grows
  • Smaller suckers can be pinched off by hand, but larger ones (thicker than a chopstick) should be clipped with scissors or pruning shears to avoid damaging the plant


Tomatoes are heavy feeders, meaning they take a lot of nutrients out of the soil as they grown. To ensure your tomato plants have enough nutrients, you can fertilize throughout the season.

If you decide to purchase fertilizer, remember to look for non-synthetic fertilizers that meet requirements for organic production. For one, it’s part of the Garden City Harvest community garden policy and sustainable gardening guidelines. One of the reasons we don’t promote the use of non-synthetic fertilizer is because they tend to deteriorate soil quality, rather than build it. Plants then become dependent on continued applications of synthetic fertilizer in degraded soil. Plus, synthetics contribute to water pollution and when used in excess can be ingested and contribute to health problems. You can read more on the effects of synthetic fertilizer in this discussion from Organic Valley. And this article better explains how to identify organic fertilizers.

Here’s the skinny on fertilizers:

  • Complete fertilizers include a balance of nitrogen, phosphorous, and potassium. All fertilizers have a ratio printed on their label which indicates that particular fertilizer’s balance of these nutrients (for example: 5-10-10 or 10-10-10)
  • Other fertilizers, such as manure, bone meal or cottonseed meal provide just one of those nutrients
  • Nitrogen promotes the growth of dark green foliage; Phosphorous promotes the growth of flowers and fruits; Potassium helps build a strong stem and root system

Here is the secret for fertilizing tomato plants:

Use a fertilizer higher in nitrogen in the beginning of the plant’s life (such as fish emulsion), BEFORE the plant starts producing blossoms. This promotes the growth of foliage, which promotes better photosynthesis.

Once the plants start producing blossoms, use a fertilizer higher in phosphorous (to help the growth of flowers and fruits)

Some tips on watering

Tomatoes are best watered at the base of the plant, rather than from over head. Watering the foliage can cause the leaves to get sunburned during the day (there’s no SPF to protect from that). Water left on leaves overnight can also lead to disease.

Throughout the summer consistently give your plants a deep watering (2 – 3 times/week). If the soil is dry one inch below the surface, those plants need a drink (mulching around your plants will help them retain their moisture). However, once the end of the season is in sight begin to water your plant a little less. Yes, that’s right. All summer long you took extra special care of that tomato plant, only to stress it out at the end of summer. By watering less you slightly stress out the plant, which triggers it to go into full fruit production.

Stay tuned for more info about extending your tomato season, harvesting, and storing tomatoes. In the meantime, leave us a comment if you want more information about a particular topic – tomato-related or not.