Learn to grow your own tomatoes

How to grow tomatoes

First, you’ll need to decide whether to start with seeds or transplants. We carry some great options for both.

We recommend the following varieties, all of which are blight resistant:

  • Mountain Merit (beefsteak; determinate)
  • Defiant (medium size, determinate)
  • Stellar (medium size, determinate)
  • Plum Regal (Roma, determinate)
  • Mountain Magic (Campari, indeterminate)
  • Sweetheart of the Patio (cherry, determinate)
  • Jasper (cherry, indeterminate)
  • Cherry Bomb (cherry, indeterminate)

Tomatoes need lots of room to grow and it is best to know if the variety you choose is determinate or indeterminate.

Determinate: These tomato plants only grow to a certain mature size, more like a compact bush variety. All the tomatoes tend to ripen more or less at once.

Indeterminate: These tomato plants will grow like vines and continue to grow all season long. They require a good support system to stay upright.

Starting from Seeds

Six ingredients to help you achieve success:

Soil: choose a good quality seed starting mix like ASB Seed & Herb Soil or Fafard Agro Mix Seed Starter.

Perlite: use perlite for the top of the soil to help with aeration and moisture control. Perlite will help prevent “damping off,” which is when excess moisture results in fungal disease that kills the seedlings.

Container: Choose the right container for your space. This depends on how much space you have. We use a standard black tray with no holes. You can also use fiber pots or peat pellets. All seed packages provide the depth at which to plant the seeds and the time frame in which to start them.

Dome: A dome helps with soil moisture retention when the seeds are first germinating and growing.

Heat mat: this will help keep the seeds warm and help promote germination.

SunBlaster light bulb: these can be installed in a lamp that you already have. We also carry the strip lights that you can hang and light up a larger area. There are lots of different sizes to choose from.

Once you have the items that you need, the next step is to plant your seeds.

How to plant

We do not recommend planting into dry soil, so make sure you moisten the soil before planting. Loosen up the soil so it does not have any big chunks in it. Smooth it out evenly on your tray, leaving about 1” at the top.  If you decide to use peat pellets, let them soak in water overnight so they can rise. Always check your seed package for instructions on what depth to plant before sowing.

After placing your seeds, sprinkle some soil on top to cover them. Then sprinkle perlite over the top of everything. Give them a drink of water but no fertilizer until the second true leaves emerge. Place the heat mat on the surface where you are growing your tomatoes and put the tray on top. Put the dome on, but do not close it tightly because you still want some air movement. Turn the lights on and set them on a timer for 16 hours on, 8 hours off. Patiently wait for your seeds to germinate. It’s best to keep the soil consistently moist;  not too wet as this will cause them to damp off. Use a smaller watering can or a spray bottle and just spritz until the soil is evenly moistened.

Transplanting from seed starting to larger container

After your seedlings have started their growing process, you will need to plant them into larger containers. You can use the same soil that you bought to start the seeds. We go from a large open tray to a 4 ½” size pot. The tomato seedlings can grow in this size pot until you are ready to put them outside, as long as they don’t get too big for the pot.

Transplanting into the garden

We don’t recommend planting tomatoes outside until the chance of frost has passed. The rule of thumb is June 10th. However, you can move the plants in and outside until it is time to plant outdoors.

Make sure your garden is prepared with the proper compost and peat moss. We recommend planting tomatoes at one end of the garden, so they do not throw shade over other vegetables that you’re growing.

Plant in a spot with a minimum of 6 hours sunlight. Dig a hole deep enough to lay your tomato down on its side. We recommend adding a tablespoon of bone meal to the hole; this will help with root development. Put your transplant in the hole and cover it up to the first or second set of leaves – this will make a stronger rootstock. After you’re done planting, give the tomato plant a good drink to soak in deep. Do not use fertilizer now.

You don’t need to use a support system at this time, but if you want to use one, it’s best to put it in right away. We recommend using a heavy-duty tomato cage or stakes. If you decide to go with stakes, make sure you use garden Velcro or tomato tie so that it does not damage the stalk or branches. If you decide to wait, do not let the plant get too large before trying to get a cage over it.

Water & Fertilizing

Once the second set of true leaves appear on your seedlings, you should start feeding. When first fertilizing only use a half strength mix of what is recommended. We carry a Miracle Gro water soluble tomato plant food that works well.

Your watering schedule will vary depending on the temperatures and how much sun your tomatoes get. You should try to water in the morning. If it is a really hot day you may need to give them another small drink in the evening. Try and keep a consistent level of moisture for the tomatoes. You do not want them to dry out or be too wet. You should start fertilizing every week to 2 weeks after planting with a water-soluble tomato fertilizer. You can also use fertilizer spikes. Please follow the directions on the package.

There are some things you should always be on the look out for.  Pests, blossom end rot, and early or late blight are the main three problems with tomatoes. Click here to learn more about blight and know what to look for.

Check your plants weekly for aphids. They usually hide underneath the leaves and can be different colors depending on where they are hiding. If you notice a bug, take a picture of it or bring a sample of the leaf in a tied bag to us and we can let you know what it is and how to deal with the problem.

Blossom end rot looks a lot like blight, but it starts on the bottom of the tomato. This can be overcome before it begins by adding calcium to the soil when the tomatoes are starting to form. We carry some suitable products such as Cal Mag, bone meal, fertilizer with added calcium etc. Even adding eggshells to the soil when transplanting can help add calcium.

Early or late blight is extremely hard to get rid of once it has started. During the growing season you can use a product like Safer’s Bordo Powder that states on the package it is for blight.

If you get blight and need to discard your plants, please do not put them into your compost pile or the green compost bin as that can spread blight. Please cover the infected plant with a garbage bag, cut the stem of the plant at soil level to carefully bag it, then tie the top and dispose of it in the waste bin (black bin in PEI). This will enable you to avoid spreading spores in the air to neighboring plants and properties.


You will likely need to prune your tomato plants. This is different depending on which variety you’ve chosen.

Determinate tomatoes. Only prune any bottom leaves that will touch the soil and cause problems later. You should prune the flowers off until your plants start to get larger. But remember: the flowers are where your fruit comes from, so only do this until the plant reaches about 1 – 1.5 ft. tall.

Indeterminate tomatoes. Prune any blossoms off until the tomato plant is about 1.5 ft. tall. Then leave the blossoms on; again, the blossoms are what gives you fruit. Make sure there are no leaves that are touching the ground/soil. Indeterminate tomatoes should only have one -three main stocks. In order to do this, you need to remove the stems that grow between the branch and the stalk; these are called suckers. This will help the plant move the nutrients to produce tomatoes and not just a lot of leaves.


We recommend waiting to harvest your tomatoes until they are ripe on the vine. This will ensure they are at their most enjoyable flavor. If you’re growing cherry tomatoes, harvest them just before they get too ripe, because sometimes they can crack. If you have a chance of frost coming you can cover your crop with a frost blanket or pick them when they are green. if you must pick them when they are green, they need to sit in a dark spot to ripen, preferably in a paper bag.