Welcome to Ask a Flower, the Q/A blog series that answers the questions you want to know!
All questions are researched and answered by the St. Andrews Garden Team. Not all questions asked may appear on this blog.
Q: What kind of tomatoes are ya'll growing?
A: We started the Spring planting with these varieties: Yellow Pear Tomato , Sweetie Cherry Tomato, Mortgage Lifter, Kelloggs Breakfast Tomato, Opalka, and Ace 55. Most of them are thriving, and we should have fruit from all of them. Unfortunately, the Mortgage Lifter variety has not survived after two unsuccessful tries.
Q: I want to grow tomatoes this year, but I've never done it before. What do I need to know?
A: The first thing you need to know is that unlike most plants, tomatoes love to be planted extra-deep. This means that when you transplant a tomato, you can (and should) snip off the lower branches and bury the stem as deep as you can. You can even dig a trench and lay the tomato plant sideways in it, gently bending the top portion so it’s aboveground as you bury the stem beneath the surface. The entire stem underground will sprout roots. Remember that your young tomato plant will soon grow into a monstrous bush that’s apt to fall over, even when staked or caged. Strong roots facilitated by a long length of stem underground are important to the plant’s future health.
The second thing a new tomato grower needs to know is something that I wish I had understood at the beginning of my planting adventures: the difference between “determinate” and “indeterminate” tomatoes. Determinate tomatoes are great for containers, people who intend to can and put up salsa or tomato sauces, or those who know they’ll be gone on vacation later in the summer. Determinate tomatoes only grow to a set size (usually around 4’) and then produce a big flush of tomatoes over the course of a couple weeks. Then they’re done for the year. Determinate tomatoes are also known as “bush” tomatoes.
Indeterminate tomatoes can’t stop and won’t stop. They grow throughout their lifespan, reaching 6 – 12’ as they vine. Once they begin flowering, they continue to produce fruit (weather permitting) until frost-killed. Indeterminate tomatoes NEED staking or a trellis. Don’t underestimate how much space these plants need when you put them in the ground as young “vine” tomatoes. It’s a good idea to prune to facilitate air circulation to help prevent diseases on these huge plants.
The third thing you need to know is that tomatoes are native to the tropical highlands of South America, and only bumble bees can pollinate them. Tomato flowers “hide” their pollen until the “buzz” vibration of a bumble bee shakes it out. It’s a great plan to plant basil and/or native companion flowers near tomatoes to bring in the natural pollinators they need. Tomatoes cannot set fruit above 85 degrees because the pollen isn’t viable in the heat (it’s hotter than where they came from). Be patient with your tomatoes from late July through early August. If you care for them during this typically overwhelmingly hot summer zone, they will begin to produce again as temperatures fall toward autumn. Enjoy the fresh fruit until frost!
Q: Some of my tomato leaves have brown spots on them. Is that normal?
A: There’s a strong chance that your tomatoes are infected with a fungus called Septoria. Like many fungi, it enjoys warm, humid weather—hello, South Carolina! Because of this, Septoria is a common tomato disease around here. It usually starts as black/brown spots with a tan border on the bottom leaves of the plant, eventually turning the leaves yellow until they wither and fall off. This process will continue to move up the plant as the fungus spreads. There are other diseases that have similar symptoms, but this is most likely what you’re seeing.
So, what now? There are several ways you can fight Septoria:
- Rain/overhead-watering causes Septoria’s reproductive spores to launch to other leaves and plants, so water at the base of the plant instead and place your plants further apart.
- Remember how fungi love warm and wet weather? Water in the morning so that the water can evaporate before night.
- Use a fungicide formulated for tomatoes.
Q: The flowers on my tomato plants keep falling off. Is that okay?
A: This frustrating occurrence is known as "blossom drop." If few flowers form on your tomato plants or the flowers drop before setting fruit, possible causes include: nighttime temperatures above 70 degrees or below 50 degrees, daytime temperatures above 85 degrees, too little sun, drought stress, and/or excess nitrogen in the soil. The most common is the weather, and that can usually be sorted out by itself once it improves.
Q: My tomatoes get lots of flowers but no fruit. What's going on?
A: Lots of flowers and no fruit is usually blamed on one or two things: 1) the temperature and/or 2) poor pollination. Similar to blossom drop, if the temperature is too warm, the flowers will fail to bloom and set to fruit. Poor pollination could be to blame by cold, windy weather limiting the amount of work pollinators put in. Or maybe there are no pollinators in the area. Try planting flowers that bumblebees like.
Q: Some of the bottoms of my growing tomatoes are brown and mushy. What is that, and why is it like that?
A: "Blossom-end rot" is the name of this condition. Blossom-end rot is not a disease, rather, it’s caused by a calcium deficiency. Unfortunately, even if there is plenty of calcium in the soil, a couple of factors can prevent the tomato plant from being able to make use of it. The first factor is water. Calcium is water soluble, so tomatoes “drink” it in their water and need to maintain a steady supply for fruit production. If tomato plants dry out too much between waterings, they won’t be able to maintain healthy calcium levels, and the fruit will begin to rot, usually about halfway through maturing. To avoid this problem, water deeply a few times a week, especially in summer heat, in the early morning.
Another factor is having far too much phosphorus in the soil, which can transform calcium into a form that is insoluble for tomatoes. The other common cause for blossom-end rot is growing tomatoes in soil that is too acidic. To avoid these problems, be sure to send a soil sample to the Clemson Extension Service every year in early spring (February – March) to check on the status of your soil and make adjustments as recommended before planting.
Blossom-end rot cannot be reversed once it has set in. However, preventative measures include consistently watering and preventing moisture loss through mulching. You may use a Rot Stop spray to reduce occurrences on the plant after it has already started to show signs of stress through rot spots.
Q: Should I be worried that my tomatoes' leaves are yellowing?
A: If the leaves of your tomato plants are yellowing, look on the underside of the leaves for aphids. Aphids will also cluster on new plant growth. Wash away aphids with a strong jet of water or use neem oil.
If you are a smoker or use other tobacco products, be sure to wash your hands thoroughly before touching tomato plants. Yellow leaves may be a sign of the tobacco mosaic virus. Leaves with the virus should be thrown away and not composted.
With all this being said, yellowing on the lower leaves of a tomato plant can be a natural stage in the maturing process because they are receiving less sunlight than their green counterparts. This is fairly common on bushy, determinate species.
Q: My tomatoes get cracks in them later in the season. How do I stop that?
A: Tomatoes split open when the skins of the ripe fruit can't keep pace with the growth of the insides—especially when that growth is sudden and rapid, like right after a rain that falls heavily in a short period of time.
A few solutions:
- Growing in raised beds. Tomatoes grown in raised beds are always going to have the problem less, because heavy rains will drain away faster in the light, loose, raised bed. Flat-earth gardeners with compacted soil will always have more cracking and splitting.
- Compost. A one to two inch mulch of compost, shredded fall leaves or straw will also help by keeping the soil moisture more constant. Again, you get the worst splitting when a lot of rain follows a very dry spell, and mulch can help keep the moisture levels higher during dry times, which helps the skins stay more flexible.
- Calcium. Having access to adequate soil calcium allows tomatoes to better regulate their water uptake. If your soil is Calcium poor, adding some at planting time may help. You can test your soil by sending a sample to the Clemson Extension Service to make the proper adjustments.
Meet the Flowers!
The St. Andrews Garden Team is led by Marigold, our resident expert on all things plant. A life-long environmentalist at heart, she is one class away from her certification in Native Plant Studies through the South Carolina Botanical Garden hosted at Clemson University and the South Carolina Native Plant Society, and has been growing her own fresh food since she was 22. She established the St. Andrews Garden in a distant corner on the property with Rod in 2014. It is now a front-and-center showpiece with the recent library remodel. Jessica and Lindsey T. were added to the garden team in Feb. 2018 and have apprenticed with Marigold since then. Lindsay W. joined their ranks in Aug. 2018 along with Steve in Apr. 2019.
Richland Library St. Andrews harvests every Tuesday morning. Come by for fresh veggies or to ask us some questions that can appear on our website in a future blog post! Or, email your questions to firstname.lastname@example.org.
St. Andrews Associate