TOMATO 101: What to do with those lovely tomato seedlings you bought on Saturday....

Tomato Planting in Calgary

“When is the right time to plant my tomatoes?” There is not a single answer for this question and optimal dates often change between years and locations. In order for you to make your decision, you must take into account Calgary’s average last frost date, the weather forecast and your soil temperature. Tomatoes cannot tolerate any frost, so if you plant them too early and they get frosted, you will have to replace them with new plants. Calgary’s average last frost date is May 23^rd so that should be your absolute earliest planting date. Because this is an average date, remember that there is a 50% chance a frost will occur after May 23^rd, so be ready to cover them if necessary. The weather forecast is

important since it gives us a view as to whether we are going into a warming or cooling trend.  The coming week’s forecast looks quite good, with frost seeming unlikely, although we all know that Calgary weather can be quickly influenced due to our location near the mountains.

 Very important to consider is your soil temperature. Tomatoes are tropical plants which like warm soil. If your soil is still very cold, planted tomatoes will just sit and not grow. For me, my home beds are still cool, but my raised bed at the community center is warm. Even with this, I won’t be planting my community garden until next weekend when things will be even warmer and the chance of frost is very low.

This year, because of the cold spring we could not get our plants outside into really good sunlight so they have grown quite tall and thin. This is not an issue since we will make sure to plant them deeply to build the biggest root systems possible. In an earlier article we had discussed that when re-potting tomato seedlings we can develop a bigger overall root system by taking advantage of the plants ability to send out roots along its buried stem. We will do the same thing again as we plant them out into our gardens. Plant them more deeply than in their current pot so roots will grow along the buried stem which is better for our dry conditions.

You should prep the plants before planting by trimming off all of the leaves which will be buried when you plant them deeply. The picture shows where to remove leaves, and as well, an indication of how deeply to plant the stem.  We remove the leaves to avoid the issue of having them continue to grow and keep popping out of the ground all summer long.

What if we have very tall plants? Not a problem since they can be planted on their side to cover up even more of their stems. The final 2 pictures show how to do this, and for a couple of my plants this year I will be using this technique.

Good luck with your planting, and we’ll see you at the gardens.

 Compost

Right now, our community garden group has been blessed with a large pile NNof top quality compost, specially shipped in for us to use in our plots.  The pile is getting smaller by the day, so you need to move quickly if you want some! It is located just west of the community centre and with the tools and wheelbarrows we have at our disposal, it could not be easier to apply.

For tomato growers, a generous amount of good compost worked into the soil is considered one of the necessary ingredients for success. Compost, aka black gold, lightens soil, adds humus, holds water and provides nutrients for plants as it rots away.  Our beds have clay based soil so the compost can help to lighten it, making it easier for plant roots to grow. If the compost is well mixed into the soil as an amendment it will help retain moisture as well, something which is important for Calgary gardeners.

How do you start? Applying compost properly is a bit of work, but it will pay off with improved plant growth and yields. Dig a wheelbarrow full of compost, dump it on top of your bed, use a bow rake to spread it out evenly, and then dig/mix it into the soil with a garden spading fork. Mix it in to the depth of the fork tines, about 8-10 inches. Mixing is important since the greatest value is only realized when it is mixed with your soil. There is little value in simply top dressing your bed since compost dries out more quickly than soil, will not lighten the underlying soil, and will stop rotting when it is dry. Complaints about the compost “drying out too quickly” will come from those who just dump it on top of their bed as opposed to mixing it in as a soil amendment.

One last tip is to ensure you mix it into your soil right up to the inside edge of the boards. Hot weather crops such as tomatoes and cucumbers are not shy about having their roots grow right up against the warm boards, so you want that soil to be as fortified as the soil in the middle of your bed.  

Determinate versus Indeterminate tomatoes

During the rush of the community tomato seedling sale you may have picked up one or more of the few `determinate’ varieties being offered for sale. To find out, check the variety tag to see if you have any of Independence Day, Polbig F1, Bush Beefsteak, Arctic Fire and/or Celebrity F1.

Everything else we sold (Sun Gold, Sweet Million etc) was an `indeterminate’ variety.

Indeterminate plants are `vine’ tomatoes which produce fruit along the length of the vine, while determinate plants are `bush’ tomatoes which produce their flowers & fruit at the end of branches only (see images). In most cases, determinate plants stop growing while they are fairly short, making them more manageable.

Neither type (determinate/indeterminate) is better, but each has to be treated in a slightly different manner in your garden in order for you to be successful.

Determinate (bush) varieties should not be pruned, can be contained and supported by tomato cages, and do not need to be staked for support. Because the plant terminates each branch with a flower axil, the size of the plant is controlled and the fruit tends to ripen within a concentrated time period of time. Early determinate tomatoes will flower, fully fruit & begin to die within our short Calgary growing season. If you have a determinate variety from the sale, just remember “use cages for support & no pruning.” The side shoots should be left on determinate varieties.

Indeterminate (vine) tomato plants will need to be vertically staked for support since they will grow out of standard tomato cages.  You can start them in a cage, but be prepared to add a stake later if you want to control the plant. As well they should be `pruned’ for best fruiting results. In our context, pruning means removing side shoots from the main stem. Because these vines will grow indefinitely – or until they are killed by frost - the fruit they produce ripens along the main stem over an extended period of time. In our climate with a killing frost, you will end up with lots of green fruit at the end of the growing season.

As an fyi, we will be producing a detailed article on proper pruning techniques and options, and doing an in-garden demonstration.

Re-potting

When re-potting tomato seedlings we can develop a bigger overall root system by taking advantage of the plants ability to send out roots along any buried stem. In Calgary, we want the biggest root system possible to help the plant survive in our dry climate, and I have found this technique helpful to do so. Please note this technique does not necessarily apply to other types of flower & vegetable seedlings.

The new pot should be deeper than the original one. Remove the tomato from the original then place it directly into the bottom of the bigger one, before adding any new soil. Fill in the spaces around the old root ball with new soil and add enough to ensure an additional length of the exposed stem becomes buried (see diagram). Within a few days, new roots will begin growing along the full length of the buried stem and these will help sustain the plant in addition to the original ones.  Be sure to remove/trim any leaves which would become buried in the process.

This method will also provide additional stem stability, and we will employ it again when we finally put the plants out into the garden.

After purchasing your tomatoes from the Mid Sun Community Garden seedling sale on Satuday, you may be asking “What do I do next?” or “What steps do I need to follow to ensure success?”  Here are a few pointers which can help you be successful.

Even  though today (Saturday) is cold, the trend for the coming week is one of general warming and it will be important to get your plants out, “hardened off” & into the outdoor sun so they can grow stronger. “Hardening off” tomatoes is the process of getting plants which were raised indoors under lights to a point where they can be grown in full sun. The process in tomatoes is similar to how we ourselves slowly increase our time of exposure to the stronger spring sun to build up protection. Humans can get a sunburn, tomatoes can get a sun scald (see picture). Sun scald is not lethal, but it is unsightly and it will definitely slow the growth of young plants.

Hardening off tomatoes takes about a week of gradually increasing exposure to sunshine to fully transition from indoor light to full sun. To start, begin by locating the plants in shade with no direct sun. After a day or two, re-locate the plants into brighter shade with an hour or so of direct sun (maximum).  From there, gradually add hours of exposure to direct sunlight each day until the plants are capable of handling full sunshine.

In Calgary, because night time temperatures remain so low, you will typically want to bring your plants into the garage at night to ensure they are not killed by frost.

Keep your plants well watered and if they begin to become root bound, you can re-pot them one more time into bigger containers before you finally plant them out.