Advice from the Help Desk of the UC Master Gardener Program of Contra Costa County
Client's Request: I purchased a Yellow Rainbow Beefsteak Tomato Plant at your annual sale in Walnut Creek this year. The plant has grown quite big and has about four tomatoes on the plant. They have stayed about the same size for about two weeks now and are not turning yellow — they are green. I have used organic tomato fertilizer, but it has not helped. Any suggestions?
It's hard to know why your tomato has been so slow to produce ripe tomatoes. However, Yellow Rainbow Beefsteak tomatoes are one of the slower tomatoes to start producing—some websites call them “fall producers”. The typical time for the plants to start producing is about 90 days from the time the seedlings go into the ground, so it does seem that your plant is a bit late. One possibility is that the soil where it is planted had excessive nitrogen fertilizer. When there is excess nitrogen, tomato plants often produce abundant foliage but set very few tomatoes. Next year, you might want to do a soil test before you plant your tomatoes. You can purchase an inexpensive home soils test kit at a nursery or big box store. The kit typically allows you to test levels of three principal nutrients—nitrogen, phosphorous and potassium (N, P, K). N is used by plants to produce green foliage; P helps with fruit production and K helps with roots and the overall well-being of the plant. Then use fertilizers only as needed to address any nutrient deficits.
You indicated that you used an organic tomato fertilizer. That likely included some amount of all three nutrients (and possibly other micro-nutrients such as calcium). If the plant was already growing well, it probably didn't need more nitrogen. Applying a fertilizer that added only phosphorous might have done the job. Also, you didn't say when you applied the fertilizer, but we are guessing you might have added it to help spur fruit production. If you applied it before the four tomatoes set, the fact that you now have those tomatoes on the plant may be a sign that the fertilizer application did help. As for the slow growth of the size of the tomatoes and their being slow to ripen, I think you just need to be patient. If is not uncommon for heirloom tomatoes to take several weeks to mature. I waited about six weeks after fruit set for tomatoes on one of my plants this year to finally grow to an appropriate size and ripen.
Tomatoes don't need to have insect pollinators to set fruit. Rather, the flowers are typically pollinated by wind action. If you have flowers on your plant that have not yet set fruit, try to duplicate the wind effect by gently shaking the plants once or twice a day, preferably mid-morning. Also, it may be helpful for you to know that tomatoes usually don't set fruit when daytime temperatures are more than 85 to 90 degrees. It's been somewhat cooler throughout our county in recent days (but not the last several days when this was edited and updated for posting) and hopefully, you may have had some additional fruit set then. But it's about to get hotter again for the next several days (or more likely cool again thank goodness). By early week when this blog is posted, it's supposed to be cooler again. Hopefully, at that time some additional tomatoes will set, particularly if you remember to shake the plant occasionally.
One final thought, keep track of how well all of your tomato plants produce and how much you enjoy their flavor. I typically try to plant at least one variety that has been a reliable producer in prior years to make it more likely that I'll get a steady supply of tomatoes. I re-plant slow producing varieties again only if I really thought their taste was outstanding and worth the wait and low production rate.
Hope you soon have some tasty tomatoes to harvest.
Help Desk of the UC Master Gardener Program of Contra Costa County (tkl)
Notes: Contra Costa MG'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: firstname.lastname@example.org, or on the web at http://ccmg.ucanr.edu/Ask_Us/. MGCC Blogs can be found at http://ccmg.edu/HortCoCo/ You can also subscribe to the Blog.
Help for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Situation: Client visited the Ask A Master Gardener (AAMG) Help Desk at a recent Wednesday morning program at MGCC's “Our Garden” asking for advice on the black spots on the fruit of his mature Meyer Lemon fruit tree. MGs on duty that morning couldn't give him a definitive answer at the time, but asked him to make some further observations about the tree and posed several questions about the health of the tree for him to answer and to send an email with his findings to the MGCC Help Desk.
Client's Response and Request: I appreciate your effort in determining the problems with my Lemon tree,
1. The tree is approximately 25 years old,
2. I bought it as a semi-standard tree. it's 18 feet tall and has a 15' canopy.
3. it's a great -year round producer of fruit.
4. The tree is located about 20' from a building, and it now gets sun all day.
5. I recently cut down a large olive tree that partly shaded the tree and blocked a lot of early morning sun.
6. I don't recall ever seeing spots on the rinds before, I have seen the inside of the fruit that looks darkened and not much juice before. I assumed that it was due to lack of water or fruit being old.
7. I fertilize the tree probably once a year with fertilizer spikes.
8. The bark looks fine.
9. The spotting on the fruit is about 20% of the total, and the leaves look good.
I'll examine the tree closer, but it's been a fantastic tree. I'll send you this now and if you need anything else from me let me know.
MGCC Help Desk Response: Thanks for coming to the UC Master Gardener Program Help Desk at Our Garden with your request for assistance with your Meyer lemon tree and fruit. Quite a few of us have spent time researching your inquiry in the past few weeks; unfortunately, we have been unable to pinpoint a specific disease or cause in order to give you a confident diagnosis.
Here's a list of what we think could be causes for your fruit decline based on our research:
- The change in the sun exposure is likely to have been a culprit, but we don't think that it is the only factor causing damage to the fruit. This problem may be resolved next year after the tree has had some time to adjust to the new light exposure.
- The high continual heat we've experienced this past summer may also have contributed to fruit decline.
- The cold wet winter last year may have caused some of the damage to the fruit.
- Oddly enough, actions you have taken to care for the tree may also have caused problems. See information in the attached link below.
We found an on-line UC article that includes many photos of various types of rind damage on citrus. There is mention in this article of many causes of fruit rind damage including: cold wet weather and frost, copper sprays, fertilizer sprays, wind damage, etc. Please take a look at this article to see if any of these causes may apply to your situation.http://ipm.ucanr.edu/IPMPROJECT/ADS/Fruit_disorders_in_citrus.pdf
We think that the best thing you can do now is to remove all the damaged fruit and give your Meyer lemon the very best cultural care you can and then you'll need to simply wait and see. Citrus are usually very hardy in our area and we think you may see recovery and improvement by next year.
Here are some tips on giving your citrus good cultural care:
- Citrus trees require moisture for growth and fruit production. Apply enough water at each irrigation to wet the soil three feet deep. This requires three to six inches of water depending on the type of soil. Here is a link to information on how to water citrus: http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/CULTURAL/citruswatering.html
- A layer of organic mulch will help retain soil moisture and permits feeder roots to grow close to the surface. Mulch should not be placed close to the trunk of a mature tree.
- Mature citrus trees are given fertilizer to maintain their growth and fruit production. Nitrogen is the chief nutrient required by citrus and should be applied each year. Smaller quantities of phosphorus and potassium are required. These nutrients are held in the soil much longer than nitrogen. Here is a link to information on how to feed/fertilize citrus: http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/CULTURAL/citfertilization.html
- Citrus may occasionally suffer from a deficiency of zinc or iron. When these nutrients are deficient, the tissue between leaf veins turns yellow, but the veins remain green, at least initially. Foliar sprays containing chelated zinc or iron can be used to correct these deficiencies. Iron deficiency can also be caused by excessively wet soil or by very alkaline soil (pH above 7).
- Citrus is ready to harvest when the fruit has colored and is mature. Your 25 year experience should suffice to know when the fruit is ripe... i.e. dark yellow. Fruit should be left on the tree until it attains a satisfactory "sweetness". Mature fruit should be carefully harvested. Any break in the rind will promote decay. Use sharp clippers to cut the stem close to the fruit. Fruit can be stored on the tree several weeks to several months, depending on variety, after it is mature. As you probably have experienced, fruit left on the tree too long will become overripe and can reduce the size of the following year's crop.
We hope you find this information helpful in bringing your lemon tree back to full production. Please let us know if you have any additional questions.
Help Desk of the Master Gardener Program of Contra Costa County (SLH)
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: email@example.com, 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/)./span>/span>
Help for the Home Gardener from the Contra Costa Master Gardener Help Desk
Client's Question and Problem:
CCMG Help Desk's Response:
I'm writing to respond to the questions that you left in your Help Desk phone message. I understand that you are growing two tomato plants in containers as well as some peppers. You mentioned that the tomatoes have produced fruit, but most of it is still very green (as of early September). You asked whether there is something you can do to speed up the ripening process.
You probably won't be able to speed up the ripening of the tomatoes. The timing of getting ripe tomatoes depends both on when you started the tomatoes and on the variety you are growing. In my own garden, I planted eight different heirloom varieties this year. Two of them are in pots. I planted seedlings from four inch pots in early April. Most of the tomato varieties starting giving me quite a few ripe tomatoes by late July. However, one of them only produced an occasional ripe tomato until about a week ago, when I started being able to harvest three or four ripe tomatoes per day. The two tomatoes I have growing in containers are likewise producing ripe tomatoes at different rates. One has produced many ripe tomatoes and only a few green ones remain on the plant currently. The other was much slower to start producing ripe tomatoes. I've picked quite a few of them, but it still has lots of green tomatoes which I know will continue to ripen over time.
So my advice is just continue to be patient. For earlier tomatoes next year, you could pick a variety that produces early fruit. Or, if the weather cooperates, you might be able to plant your containers somewhat earlier next year. (I generally wait for night time temperatures to regularly reach 50 or above before planting. That target temperature occurred somewhat earlier this year than it does in many years.)
As for your question as to why your pepper is producing green peppers when the variety is supposed to be red, again the answer is that you'll just need to be patient and wait a while longer. All pepper varieties start as green peppers. With time, varieties that produce other colors will begin to ripen and change color. It sometimes takes several weeks after the green peppers have developed to their full size before you will start seeing a color change.
Both peppers and tomatoes can easily be sunburned. The sunburned area turns a light brownish color. It's still fine to eat the fruits, but you generally have to cut out the sunburn. To prevent your green tomatoes and peppers from getting sunburned, try to be sure that the developing fruit has some leaf cover. If not, you can also erect some type of sunshade to keep the sun from scorching the fruit.
Finally, as we approach fall and cooler temperatures, you may find that the ripening process slows. I generally leave my tomatoes in the garden if they still have green fruit until the night-time temperatures start to dip into the 40's. Tomatoes are quire cold sensitive so the plants will start dying when the weather cools. At that point, I harvest all the green tomatoes and put them on my kitchen counter. They will continue to ripen there. The fruit that ripens that way isn't as wonderful as a vine-ripened fruit, but it's still better than what you can buy in the grocery store. Unfortunately, peppers won't change color after you harvest them, but the green colored peppers can be just as tasty as those that have taken on their ripe color.
A post script...
I hadn't realized from your phone message that the main question you have is “Why has the ripening of the tomatoes slowed down so much from what it was in prior years?” Thanks for clarifying.
Here are a couple of possible causes.
- A key resource that tomatoes need for ripening is plenty of leaf surface for photosynthesis. Often by late summer, some of the leaves on the tomato have started to dry up and wither and are no longer helping to nourish the plant. The plant is less vigorous than it was earlier in the season so it takes longer for the green tomatoes to ripen.
- High temperatures are also a major cause of slow ripening. The tomato plant produces several compounds that are needed for tomato ripening. When the air temperature rises above 85 degrees, tomatoes stop making carotene and lycopene pigments, two of the most important components in the ripening process. We have had some recent hot weather spells which are probably affecting your tomatoes in this manner.
- Finally, soil temperatures are also important. For optimal growth, tomatoes need soil temperatures that are less than 80 degrees. Hot air temperatures raise the soil temperature. Containers may be particularly vulnerable to soil temperature rise if they sit in the hot afternoon sun. Mulching can help keep soil temperatures lower. Also, if your tomatoes are hit by afternoon sunshine, you might consider erecting some shade barriers to keep the sun off the containers.
If you've run out of patience with slow ripening tomatoes, one thing you can do to speed up ripening is to remove some of the green tomatoes. Then the tomato plant can put all its energy into ripening the tomatoes that remain on the plant. You can ripen the green tomatoes you remove on your kitchen counter. As I responded earlier, they won't be as yummy as the ones that ripen on the vine, but they're still better than store bought tomatoes.
As a final caution, don't be tempted to fertilize the tomato plant thinking it will speed up production. Fertilizing now will probably just cause the tomato to go into a vegetative growth mode that is too late in the season to be helpful.
Hope the above explanations clarify what is occurring. You're welcome to contact us with any additional questions.
Contra Costa Master Gardeners Help Desk
Editor's Note: The Contra Costa Master Gardener Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523.