Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County

Client's Request:  I've just set up a small garden greenhouse. It has a heater, warming mats, fans, etc. I'm thinking about growing tomatoes during the winter. Would you please provide some advice on such a venture?

Help Desk Response:  Thank you for your email to the UC Master Gardener Program Help Desk about growing tomatoes in the winter in a (warm) greenhouse. 
 

This is a great project… something I've considered at times with my greenhouse, but have yet to try. Tomatoes are really a (tender) tropical perennial that can survive and produce for several years given the appropriate growing conditions, primarily eliminating cold conditions along with proper lighting. Other members of the Solanaceae family besides tomatoes (e.g., egg plants, peppers) can also be “overwintered” with proper protection and appropriate growing conditions. On the garden radio programs I listen to, overwintering peppers in pots in greenhouses to get a fast start on their second year of growth is apparently a current favorite.

It appears that University of California does not have significant information on growing tomatoes in a greenhouse for the home gardener. However, I've listed below a few links to reputable articles from other sources that may be helpful in setting up and growing tomatoes in a greenhouse at home.

• This website from the University of Oregon, Department of Horticulture, has information on fertilization, soil, temperature and light, which may be helpful. Though the information is for commercial growing operations, some of it is applicable to home greenhouses. http://horticulture.oregonstate.edu/content/tomato-greenhouse
  
  
• This link to SF Gate discusses good tomato varieties for greenhouse growing conditions and also, mentions ways to support the growing plants. https://homeguides.sfgate.com/types-tomatoes-greenhouse-production-30810.html
  
  
•  This Wikihow website has some helpful information on various aspects of growing tomato plants in greenhouses.  https://www.wikihow.com/Grow-Tomatoes-in-a-Greenhouse

There are also many other web sites and YouTube videos available on the subject, but I would use them cautiously, and cross-check other references if they seem “too good to be true”.

Please contact us again if you have further questions. Good luck with your winter tomatoes.

Help Desk of the UC Master Gardener Program of Contra Costa County (SMT)

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Note:  UC Master Gardeners Program of Contra Costa's Help Desk is available almost year-round to answer your gardening questions.  Except for a few holidays (e.g., last 2 weeks December), we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 2380 Bisso Lane, Concord, CA 94520. We can also be reached via telephone:  (925) 608-6683, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/. MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog  (//ucanr.edu/blogs/CCMGBlog/)

Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County

Client's Request: Why no tomatoes? Starting to get lots of flowers but almost NO tomatoes? Plants look very healthy. Live in central County

MGCC Help Desk Response: Thank you for contacting the UC Master Gardener Program Help Desk with your question about no fruit but lots of flowers on your tomato plants

There could be several reasons for lack of fruiting in tomatoes:
-- Night temperatures too low, below 55ºF (12.8ºC);
-- Daytime temperatures too high, above 90ºF (32.2ºC).
The plants will produce when temperatures become favorable. Note, though, that heirloom tomatoes can be fussier about temperatures than most hybrid tomatoes and in some areas can wait until late summer or early fall to start setting fruit.
-- Excess nitrogen fertilizer. Lots of healthy green leaves and stem growth, but few flowers or fruit.
-- Too much shade – you need a minimum of six hours of sun to produce fruit.
-- Lack of pollination. While tomatoes are self-fertile, the conditions mentioned above will inhibit pollination.
-- Plants set out too early in spring. -- We recommend planting tomato seedlings the first of May; often earlier planting of seedlings will be inhibited by cold temps and they will just “sulk”; consistent warmer weather and nights should get them growing

Recommendations:
-- Choose varieties adapted to your climate zone,
-- Plant tomatoes in full sun,
-- Keep soil evenly moist, 
-- Avoid excessive nitrogen fertilizer, and
-- Tapping on blossom stems 3 times a week at midday when flowers are open may improve pollination and help set fruit.
 
Here is a comprehensive UC link about tomato culture, pests, diseases, and environmental disorders: http://ipm.ucanr.edu/PMG/GARDEN/VEGES/tomato.html
 
We hope this information helps! Let us know if you have any additional questions.

Help Desk of the UC Master Gardener Program of Contra Costa County (SLH)

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Note: The  UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions.  Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA  94523, although we will be moving this spring. We will notify you if/when that occurs. We can also be reached via telephone:  (925)646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/  MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog  (http://ucanr.edu/blogs/CCMGBlog/)

Advice for the Home Gardener From the Help Desk of the
UC Master Gardener Program of Contra Costa County

Client's Request: Hello, I am a retired cattle rancher and farmer. Although I did not farm tomatoes, for years I did rent some of my farm ground to tomato growers. As you may know, they would only grow tomatoes on the same field for no more than 3 years due to soil-borne disease. I now live in a suburban setting ion in Contra Costa County and have a small garden area that I grow tomatoes on. My question is, what can I do to continue to grow healthy tomatoes on the same ground year after year? I prefer to grow medium to large tomatoes. Can you suggest varieties of tomatoes that are resistant to these diseases? My garden area is approximately 12' by 18'. Would it do any good to grow the tomatoes one year on one half and then on the other half the next year? Then repeat this rotation year after year. Thanks for your help.

MGCC Help Desk Response: Thanks for contacting the UC Master Gardener Program with your questions about growing tomatoes in your home garden.

As you are already aware, growing tomatoes in the same place year after year can favor a buildup of pests and diseases, while rotating many vegetable crops in the garden not only enhances soil fertility but can be effective against insect and disease pests that develop on a narrow range of vegetable plants. Moving crops to different sites isolates such pests from their food sources and reduces the chances that pests will gain a permanent foothold in your garden.

We strongly recommend that you not plant tomatoes or other plants in the Solanaceae (nightshade) family such as tomatoes, sweet and hot peppers, eggplants, and potatoes in the same garden area more than 2 years in a row. You may be interested in this informative UC reference called ‘Growing Tomatoes in the Home Garden'. This free reference includes tomato culture suggestions, a list of tomatoes that includes fruit size and disease resistance, and a list of common pests and abiotic disorders. This list is not inclusive of the many, many tomatoes available, but it will provide information on tomato plants that are resistant to certain diseases. Keep in mind that there aren't any tomatoes that are completely immune to common tomato diseases! http://anrcatalog.ucanr.edu/pdf/8159.pdf

The links below offer even more information and suggestions about crop rotation strategies in the home garden. For example, moving vegetables back and forth on a smallish garden plot may not be enough to protect against pests unless you plant in raised beds to increase separation of crops:
crop rotation: http://ucanr.edu/sites/ucmgnapa/files/160975.pdf
vegetables & sustainable: http://cagardenweb.ucanr.edu/Vegetables/?uid=6&ds=462
crop rotation strategies: http://ucanr.edu/sites/gardenweb/files/29029.pdf

In case you are interested in building raised beds, this Sunset Home and Garden article is a good one: https://www.sunset.com/garden/perfect-raised-bed

You may also want to consider joining us in April for our annual tomato sale. Here is a link for more information, especially when the lists are published, of the heirloom and hybrid tomatoes you might find fit your desired types: http://ccmg.ucanr.edu/EdibleGardening/GreatTomatoPlantSale/

We hope you find the above references helpful! Good luck with your tomatoes this year!

Help Desk of the UC Master Gardener Program of Contra Costa County (SLH)

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click here for details on the Great Tomato Plant Sale

Note: The  UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions.  Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA  94523, although we will be moving this spring. We will notify you if/when that occurs. We can also be reached via telephone:  (925)646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/  MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog  (http://ucanr.edu/blogs/CCMGBlog/)

Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County 

Client's Request (from telephone conversation):  Help!... I'm growing tomatoes in an enclosed courtyard. I'm now seeing tomatoes disappearing and some with gnawed portions of low hanging tomatoes. I've heard a lot about voles being quite prevalent this year. Do you think it is voles? Other than the disappearing tomatoes and gnawing, I haven't really seen signs of other “animals”.

MGCC Help Desk Response: Thank you for calling the UC Master Gardener Program Help Desk this morning with your question about your disappearing tomatoes.

Although you suspect voles in your courtyard, they are an unlikely culprit in this case because the garden area you described is entirely enclosed except for the roof area, which is open to the sky. In order to enter the garden area, an animal would need to climb, and voles are poor climbers. It is true that Contra Costa County has had an explosion in the vole population this year, but nevertheless it does not seem likely that they are your culprit.

On the other hand, rats are excellent climbers and though somewhat larger, look similar to voles. (Voles can be up to 8 inches long, including the tail, and they have a short tail. While rats are much larger than the common house mouse or meadow vole, a young rat is occasionally confused with a mouse. In general, very young rats have large heads and feet in proportion to their bodies, whereas those of adult mice are proportionately much smaller).

Rats are very common in most neighborhoods. There are two common types of rats: Norway rats (Rattus norvegicus) and roof rats (Rattus rattus). Both are active at night. Either one could be eating your tomatoes, although roof rats are the more likely culprit, since they favor fruits. Rats could be entering your courtyard garden from the roof top opening, or they could already be resident in your attic or building.

Reducing the rat population should be the first step in protecting your tomatoes. Sanitation and making your courtyard less hospitable to rats, can go a long way to reducing the population. If you have bird feeders, either remove them or clean under them daily and take them inside at night. Also, talk with your neighbors about reducing rat habitat, as this is usually a neighborhood-wide problem. (Rat habitat outside of your courtyard might include woodpiles, moist areas in and around gardens, and dense vegetation such as ivy.)

Trapping can also work to reduce the population, but it is difficult to make a permanent dent in the population through trapping alone. Snap traps are the best traps to use as long as you can place them where other animals (squirrels, opossums, and birds as well as your dog or neighbors' cats) can't get to them. For roof rats, the traps should be placed in off-the-ground locations such as branches or fences.

If you use traps, check them frequently for dead rats. Do not touch rodents with your bare hands. Make sure you wash your hands thoroughly after handling traps. Dispose of dead rats by burying them or by placing them in a sealed plastic bag and putting them in the trash.

In the meantime, physical barriers can be used to protect your tomato plants directly. One approach is to erect a 1 foot tall barrier using metal roof flashing (obtainable at the hardware store) all the way around the planting bed. Rats are unable to gain traction on the slippery surface. Alternatively, you could build a small-mesh (no larger than 1/4 inch holes) enclosure around the bed or around each plant. Since rats, especially roof rats, are excellent climbers, the wire mesh enclosure would need to go up the sides and across the top of the plants.

We do not recommend use of rat poisons, especially out of doors, due to risk of harm to wildlife and pets either by eating the poison directly and/or indirectly in eating the rat.

For more information on rat identification and management, see: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74106.html

And for information on voles see: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7439.html

Hope this information helps you eliminate those disappearing tomatoes. From the inquiries Master Gardeners have received about rats this year you are not alone.

Please let us know if you have further questions.

Good luck with your tomatoes!

Help Desk of the UC Master Gardener Program of Contra Costa County (MCW)
Please Join us at "Fall for Plants" on September 9 for the workshops and the plant sale, Registration is optional, but it'll get you a free plant from the sale. Hope to see you there.

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Note: The  UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions.  Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA  94523. We can also be reached via telephone:  (925)646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog  (http://ucanr.edu/blogs/CCMGBlog/).