Article 6-1 Cherry Tomatoes

I am not a very patient person and waiting for tomatoes to ripen seems to take forever. Cherry tomatoes grown hydroponically in my greenhouse are at least 10 days earlier than full-sized tomatoes and I can enjoy delicious vine-ripe cherry tomatoes in less than 60 days. I start the seeds in pre-soaked jiffy pellets in early to mid-March using a metal-halide light and a constant temperature of 28°C. for germination. Once the seedlings are about three cm high, I reduce the night temperature to 20°C. The Jiffy pellets are flood-irrigated with one-quarter strength all-purpose (20-20-20) fertilizer three times a day. I leave the lights on for 15 hours/day.

The seedlings are transplanted in two to three weeks into six cm. peat pots filled with a vermiculite/perlite medium. In mid to late April, the peat pots are transplanted out to the greenhouse. I have an 11 x 12 meter double-poly greenhouse. The tomato plants are about 10 cm. in height at this point, and have two to three real leaves. The lip of the peat pots should be torn off from around the plants so that the pots do not wick away moisture. I transplant the peat pots into doubled white plastic garbage bags, which are filled with a 1:1 ratio of medium-grade vermiculite/perlite medium. The plant-roots will grow right through the peat pots and into the medium of the bags.

My greenhouse is set up with 3/4″ black plastic hose feeder lines which carry nutrient solution from the nutrient pails out to the 1/2″ black plastic hose feeder lines, which in turn feed 0.06″ spaghetti tubing directly into the plant bags. Each kitchen garbage bag holds about 12 liters of vermiculite/perlite medium. Each bag has two plants transplanted into it by making a slit in the top and setting the plant down into the medium. The bags are pre-soaked about a week ahead of time. The day before transplanting, I cut three cm. slits around the base of each bag, about three cm. from the floor for drainage. Each plant has one spaghetti line feeder at the base of the plant stem, held in place with a weight. When first set out, the plants are watered twice daily until they are well-established. The plant bags are kept warm with a system of hoses beneath the bags in which warm water is circulated.

When the plants reach a height of about 10 cm, I attach each plant to an individual string, which is attached to the rafter above and tied around the base of each bag. The plants are attached to the strings using tomato clips, one under each fruit truss. This helps support the plant as well as the trusses of fruit. If you wrap your plants around the string instead of using clips, always wrap the plants clockwise. Tomato plants grow very quickly in this climate-controlled setting and will reach a height of about one meter in only six weeks. By September, when my greenhouse is winding down, my cherry tomato plants are trying to grow higher than the three meter rafters. I trim the growing point of each plant as it reaches the rafter, encouraging the formed fruit to ripen before winter sets in.

Each day, between 10:00 am and 2:00 pm, I pollinate the tomato plants by running a small paintbrush over the trusses of flowers. This also gently shakes the plants up on a regular basis which makes the plant stems thicker and sturdier.

My nutrient solution is tested daily for pH and EC. A pH of about 6.5 is ideal, and I run my EC at 1600 mS. This is lower than is recommended by most hydroponic growers but, through trial and error, I have found that this works very well in my greenhouse. As more flowers appear, I change from a leafy formula to a fruiting and flowering formula which is higher in potassium. When we have prolonged cloudy, cool conditions, which is not very often in West Central Saskatchewan, I enrich the formula slightly. My dugout water is of excellent quality for plants, with low salt content. The concentrated nutrient solution is held in two pails with calcium nitrate in one pail and the remainder of the salts in another. Each pail has a hozon- injector which mixes the concentrates with water into a third pail which in turn, feeds the plants. By using concentrates, I mix up my solutions only once a week, instead of daily. A test-pail catches a sample of the nutrient solution and serves to indicate when I have a malfunction with my watering system or the watering lines are blocked. Blocked spaghetti tubing is one of my biggest problems and I am always on the lookout for too little over-drain. There should be 30% over-drain during sunny, warm weather, and 10% over-drain during cloudy, cooler weather. The over-drain seeps through drainage channels beneath the greenhouse which are filled with gravel. The over-drain fertilizes the large trees that surround the north end of the greenhouse. During the peak of the tomato season, there are up to twelve irrigation cycles a day, beginning one hour before sunrise, and ending one hour before sunset. The large plants use almost 10 liters/day on hot summer days.

Pruning begins when the plants have three sets of true leaves. Each inter-nodal leaf is removed at the base to ensure that the plants are not producing more leaves than tomatoes. At the end of June, I begin to remove older leaves; about two older leaves per week. These leaves are usually starting to turn yellow by this point, and are removed to help with air circulation. I do not do any truss pruning, although this is something that I may experiment with this year.

The cherry tomato cultivars that I grow are all indeterminate. I have tried a few determinate cultivars but find that they produce well until mid-season, and then shut down production just as the indeterminate cultivars are really in full swing.

Some of the most easily identifiable problems with tomato production are:

  1. Blossom-end rot – one of the easiest problems to cure, but most new growers will find some degree of this in their first growing year. This is a calcium deficiency most commonly caused not by lack of available calcium, but rather by irregular watering practices. Tomatoes can not be dried out to the point of withering, and then be watered profusely. This will almost ensure that whatever fruit is forming will have blossom-end rot. Ensure regular watering and watch for blocked water lines.
  2. Yellow foliage – indicates a nitrogen deficiency.
  3. Purple tinge indicates a phosphorus deficiency. This can occur when temperatures dip below 15°C for extended periods of time.
  4. Tobacco Mosaic Virus – plant only seeds which are resistant to this nasty virus. This virus is not treatable and the entire plant should be removed immediately.

I try to stick with cultivars that are as disease-resistant as possible. Tobacco Mosaic Virus is indicated by TMV on seed packages and it can make short work of your entire tomato crop. The cultivars that I highly recommend are:

‘Sweet Million’ – My favorite cherry tomato and best producer by a long shot. The plants are covered with a blanket of tomatoes by July. Very sweet three cm. fruits are crack-resistant. I have not had a single disease or bug problem with this cultivar in over a decade of growing. Resistant to Tobacco Mosaic Virus, Verticillium, Fusarium Wilt, and Nematodes. 60 days.

‘Sweet Gold’ – Neighbors and friends request this bright yellow cherry tomato, claiming that the flavor is sweeter than ‘Sweet Million’. They look beautiful in a salad. Although less prolific than ‘Sweet Million’, this is a cultivar I include in my regular planting. Fewer tomatoes/truss and fewer trusses/plant than ‘Sweet Million’ but fruit-size is slightly larger. Resistant to Tobacco Mosaic Virus, and Fusarium Wilt. 60 days

‘Sweet Orange’ – I grow this tomato more for interest than anything else. Their unusual color stands alone in a salad or on a vegetable tray. They are not very good producers, and I have found the ripe tomatoes are more prone to fruit-cracking, but still interesting enough for me to grow one or two plants each year. Same disease resistance as ‘Sweet Gold’. 60 days.

‘Sungold’ – An orange-colored tomato with a very distinctive, tropical taste. Very high sugar-content. Long trusses of fruit. Resistant to Tobacco Mosaic Virus, Verticillium, and Fusarium. 60 days.

‘Sakura’ – A new cherry tomato that is very disease resistant. Shorter fruit trusses with only 20 tomatoes/truss, but excellent flavour. Very firm tomatoes are good keepers. Resistant to Tobacco Mosaic Virus, Fusarium Wilt, and Cladosporium. 70 days.

There are many new cherry tomato cultivars available, such as ‘Mini Charm’ and ‘Santa’ and I intend to trial-test them in my greenhouse this summer. Make room in your greenhouse for just a few cherry tomatoes this summer and you will be enjoying the fresh taste of home-grown tomatoes extra-early this year.