Q: I know that the letters on tomato labels mean that they are resistant to certain diseases, but I have no idea what these diseases look like and whether I need to pay attention to these labels.
A: I think tomatoes can be more demanding than roses in some cases. It seems that there’s always a bug or disease ready to ruin your plans for homemade salsa.
Tomatoes are susceptible to several viruses and soil fungi, and, once infected, cannot be effectively treated. The best way to avoid this issue is to grow resistant varieties.
Tobacco Mosaic Virus (TMV) causes an irregular light green/dark green pattern on leaves and spindly, scraggly growth at the tips. Leaves can become wrinkled and sometimes frilly in appearance. The fruit from an infected plant is edible but will have low quality and poor yield. Don’t handle plants after smoking because the virus can be transmitted from tobacco to tomatoes. Look for “T” on the plant label, which indicates resistance to Tobacco Mosaic Virus.
If only one side or branch of your tomato plant turns yellow, followed by the rest of the plant gradually yellowing and dying, you have Fusarium wilt. This is caused by a soil fungus and affects tomatoes only. It’s more common in warm areas such as Southern California. A cross-section of the main stem will show dark reddish-brown plant tissue (instead of the healthy white or light tan). Varieties labelled with “F” or “VF” are resistant to Fusarium.
Verticillium wilt is more common in cooler areas and is caused by a soil fungus. Older leaves will turn yellow and die, and you will see yellowing between the veins of younger leaves. The internal stem will show tan patches, and symptoms worsen when the plant is loaded with fruit or is under some other stress. Verticillium affects many plants other than tomatoes. Don’t grow tomatoes in the same spot year after year, and choose varieties labelled with “V.”
Q: I have tried growing my own onions by planting sets that are sold in the store, however, they rarely produce a nice round bulb. Why?
A: Onions are biennials that are often grown as annuals. They can be grown from seed, transplants, or sets. Sets, which are widely available, are the quickest way to get a crop, but, depending on your climate zone, may not be adapted to produce bulbs. They can be harvested as green onions when young. The oblong mature onions are useable but don’t keep as well as a cured onion bulb.
If you desire to grow your own onion bulbs (and have patience), I recommend growing from seed. They require thinning, but you can still use the immature plants as green onions. When you see a plant that forms a bulb, allow it to produce seed and plant those seeds. Repeat this process until your seed-grown plants produce bulbs. Now you have an onion variety that is adapted to your climate.
Or, you can purchase a 50-pound sack of onions at your local warehouse store and grow tomatoes instead.
Have gardening questions? Email gardening@scng.com.
Looking for more gardening tips? Here’s how to contact the Master Gardener program in your area.
Los Angeles County
mglosangeleshelpline@ucdavis.edu; 626-586-1988; http://celosangeles.ucanr.edu/UC_Master_Gardener_Program/
Orange County
ucceocmghotline@ucanr.edu; 949-809-9760; http://mgorange.ucanr.edu/
Riverside County
anrmgriverside@ucanr.edu; 951-683-6491 ext. 231; https://ucanr.edu/sites/RiversideMG/
San Bernardino County
mgsanbern@ucanr.edu; 909-387-2182; http://mgsb.ucanr.edu/
