Thursday, March 10, 2011

Garden Blog Series: Tomatoes

Tomatoes are warm weather loving plants. As a Northern gardener near the 45th parallel in the Willamette Valley of Oregon, I need to get a head start on these plants in the late winter to be sure to get the ripened fruit I am hoping for. You can simply grow shorter season variety tomatoes if living in the North but I like varieties that are longer season tomatoes, which requires that I get started early. Some people in my area simply purchase local grown greenhouse tomato plants and don’t bother to start their own. That is certainly another option. Since I start my own tomatoes it means I plant seeds late February in the greenhouse or in my house depending on the weather. If I had a heated greenhouse I would always plant them in the greenhouse but in February it is often too cold in the greenhouse to start them in there. Once they start growing they will need to be in a heated greenhouse or in some type of environment you have created to keep them warm but still give them plenty of light.  Putting them on a greenhouse heating bed is helpful to both germinate them and keep them warm if the weather is not warm enough in an unheated greenhouse or cold frame. They need to have the soil temperature at 60-70 degrees for germination and they like air temperature of 70-75 degrees when growing. They like the night temperature to go down to 55 degrees. However, they can get unhappy if the temperature is less than 50 degrees and it will slow their growth down and you may get damage. Even so, once mine are germinated, I keep them in the greenhouse that is often around 40 at night, with dips occasionally lower and they still do OK as long as the days warm up. They would just do better if it was 50 at night.

When deciding which tomatoes to grow you want to think about how you will use them. Do you want sauce tomatoes, drying tomatoes, or fresh eating tomatoes? Also consider if you want determinate or indeterminate tomatoes.

The determinate or “bush” tomatoes will grow to a compact height of about 4 feet while the indeterminate or vine type varieties will reach heights of 6-12 feet, although 6 feet is more the norm.

The determinate variety stops growing when fruit sets on the terminal or top bud. They ripen their crop over a short period of time and then die. This is handy for someone who wants to freeze or can the tomatoes all at one time.  Determinate varieties are best as container plants. You do not want to prune determinate type tomatoes. This will decrease the amount of tomatoes you harvest. You may end up with little to no fruit from pruning determinate tomatoes.

The indeterminate type will grow and produce fruit until frost kills them. They will be blooming, setting fruit and ripen fruit all throughout the growing season. Indeterminate tomatoes produce a higher fruit yield per square foot compared to the determinate tomatoes. They will require caging or staking to support them. Pruning and sucker removal is helpful with the indeterminate type.

Using your own seed: Tomato seeds have a jelly like substance on them when taken out of the tomato. This jelly substance contains constituents within it that keep the seeds from germinating. This is removed via a fermentation process usually and we will discuss that later in the year when I go over collection of seeds from your plants. Some of the chemicals may still be on the seed and decrease its ability to germinate. Soaking the seed in water overnight will help remove some of it and help the seed to soak up water to help it germinate. This is not necessary; it just helps increase the percent of seeds that germinate. (We will discuss seed collection of various seeds later in the year.)

I plant my tomatoes in seed trays. One seed per each tray cell. A general rule for planting seeds is that they should be placed as deep in the soil as they are wide. This is not very deep for tomatoes. However, tomato seeds will not germinate as well if light gets to them, so make sure you get them well covered with about ¼ inch deep soil. Push the soil lightly down on top of the seed and it is ready to water. They should germinate in 5-14 days. Here is a great germination table for various plants.

Once they have sprouted, you should move the plants to a greenhouse or other well sunlit area that remains relatively warm. If necessary you can temporarily grow them in a window that has non “low UV panes” and an additional UV light will help immensely.  The closer they are to the window, the better they will do. You will notice the plants in tray cells closer to the window will be stronger and less spindly than those farther from the window. A UV light hung over the tray will help strengthen all the plants. If they are in a greenhouse you won’t need the extra UV light of course. Remember if the plants are indoors, they prefer to have cooler nights than days. Keep them in the 70’s in the daytime if possible and 50’s at night. Attempt to get a temperature close to this any way. Remember from the Onion Blog that the length of time our plants have light on them will affect our plants. If we give them light at night it will extend the day length for them. What this does to tomato plants is cause them to mature late and you get less fruits from the plants. So turn off their UV light and all other lights in the room at the end of the day or you need to cover them so your house light does not reach them.

Once your tomatoes start to grow, they will soon need to be transplanted into a 4-inch pot. Set them into the soil of the 4-inch pot so the lower leaves are just above the soil. Tomatoes will grow roots out of all parts of the stem that you bury in the soil. Not all plants do this, so don’t try it will others or you may damage the plant. Usually you replant a plant into a bigger pot with the soil coming to the exact same height on the plant as it had been in the smaller container. Tomatoes are different. You can plant the lower part of their stem and it will start growing roots out of the stem.  This is helpful if your tomato plant has not had enough light and has become a bit leggy. Just plant the lower leggy part and it will increase the rooting area. I pinch off any leaves on this leggy part before putting the stem in the soil. It helps to pinch them off a few days ahead of time so they have time to heal the wound. It is best not to have the freshly wounded area in the soil due to disease growth. You will want to get the tomatoes out into a cold frame as soon as possible in your area. Depending on the weather in your area, you may need to pot up to a larger pot one more time before planting in the garden. Remember it is best for them to have night temperatures above 50 degrees in whatever enclosure you have them. If you do put them out in your garden when the nights are chilly, at least put some sort of protection around them.When the risk of frost is over, you can plant them out into the garden.

When planting a tomato you need to think about how you will support it and if you will prune your tomato plants. This will make a difference as to how close you plant them. There are as many ways to grow a tomato plant as there seem to be gardeners. If I am caging an indeterminate tomato, I give them about 3 feet on center to plant them as they will grow wide and quite tall. They will even cascade over the large cage.  I will usually prune the indeterminate tomatoes to fit my cage better. No pruning necessary on the determinate tomatoes. When I am staking an indeterminate tomato I can plant them fairly close to each other as they will be vining up a stake and not be growing outward so much due to my pruning them. The small ready made cages sold in stores are generally worthless as far as I am concerned. I make cages for both determinate and indeterminate tomatoes from field fencing that is sold at animal feed stores.  This fencing is  3’ high or taller and I can make it as wide as I want by simply encircling it around itself and cutting the wire the width I want. I usually make the cage about 2.5-3 feet in diameter. I keep reusing the same cages every year. My current cages have been in use for eleven years. I use recycled re-bar that I shove into the woven fence on each side to keep the cage from falling over later when the plant is heavy with fruit and starts to push on the cage.

The indeterminate plants must have support or they will be running all over the ground. I either use a cage or I stake them. Using a cage and not pruning them can work as long as they get good air flow but if fungal growth is a concern or if you want to get larger tomatoes, I suggest staking and pruning your indeterminate plant. This usually is the best way to go. Where I live I have to use a cage or stake the indeterminate tomato plants, as there is a lot of humidity and tomato plants lying on the ground often leads to tomato plants with fungus. Plus the dense mass of leaves reduces the plants ability to get sun on all the leaves. This leads to smaller, later and less fruit. They really do best with support.  Here are a couple great videos on pruning staked indeterminate tomatoes:

Regarding the soil that a tomato likes: Tomatoes like a ph between 6 and 6.8. They like compost that is fully composted. They require moderate amounts of nitrogen and phosphorus. If your leaves are turning purple, they lack phosphorus. Too much nitrogen will give you a healthy, leafy tomato plant but you will get more leaves and less tomatoes. They also like moderate to high levels and potassium and calcium. If you don't have enough calcium in your soil you are more likely to get blossom-end rot. Don't plant a tomato in soil where another tomato, potato, eggplant, or pepper has been planted within the last three years. They all share diseases in this Solanaceae  or nightshade family and replanting one of these members of the family in the same spot successive years will increase your chance of a diseased plant. While speaking of disease, I will also mention tobacco mosaic virus. This virus can often be found on tobacco and on the hands of people who smoke. Don't let a smoker touch your tomato plants and if you smoke, wash your hands well before handling your tomatoes.

One interesting thing people grow tomatoes in is un-composted food. YouTube has some entertaining videos made by gardeners growing tomatoes in "garbage" or what I would simply call un-composted food. 

Tomatoes are thought to be self pollinating. However, in reality they need a little wind on them to ensure pollination.  The honey bees don't seem too thrilled with tomatoes but the bumble bees seem to like them. Even without anything but the wind they will pollinate themselves. The wind causes the pollen from the anthers to drift onto the stigma and fertilize the ovary. However, if they are in a greenhouse where there is no wind, they must be shaken slightly or some method of air movement needs to be used to make sure they get pollinated.

Tomato blossoms sometimes fall off. What causes this? They need to be fertilized within 50 hours of opening for the fruit to successfully set.  The embryo formed at fertilization produces auxin which helps the flowers to set.  The correct amount of auxin is necessary or the flower will fall off. Low temperatures below 55 degrees fahrenheit slows down availability of the auxin and the flower falls off. Temperatures higher than 74 F at night or 100 during the day will also make flowers fall off. 

It is important to let your tomato ripen on the vine. The last stage of ripening is when the sugars and vitamin C give the tomato its flavor. Immature tomatoes can be picked, ripened off the vine and eaten but they don't taste like those vine ripened tomatoes.

When watering tomatoes make sure you keep their leaves dry. This is very important as wet leaves lead to fungal disease. For this reason they do best with drip irrigation.


  1. nice idea.. thanks for sharing..

  2. Have you ever tried to grow and ripen your tomatoes inside your home? I've tried a few times, but I have no success yet. I live in Fulham, London, and the weather is cloudy and rainy most of the time.

    Regards, John, a gardener from Fulham