Posts Tagged: Plant Production
How's Your Okra Doing?
Advice From the Help Desk of the
UC Master Gardener Program of Contra Costa County
UC Master Gardener Help Desk: I did some research to determine possible causes for the reduced production of okra in your garden this year as compared to last year. I suspect that the high daytime temperatures that we've experienced on and off throughout the summer have contributed to the reduced production. My research also indicates that temperatures above 90° F (some sources say above 95°F) can interfere with pollination of okra and cause flowers and buds to drop. You reported in your latest message that you have noticed some encouraging signs that more pods may have started forming recently, which could be the result of the cooler temperatures that we had for several successive days last week.
Of course, we also experienced high temperatures from time to time last year when you report that production was much higher. So, there may be some other factors at work. You mentioned that you were doing some supplemental watering for the okra last summer to add to what was provided by your scheduled drip system. My research did indicate that water stress can also reduce pollination rates for okra. So perhaps the reduction in watering this year has also contributed to the reduced production rate.
One other consideration could be the fertility of the soil. Too much nitrogen will encourage lots of green growth but can suppress fruit development. Also, plants need adequate phosphorous which supports blooming and fruit production. If you have a soils test kit, it might be worth checking the fertility levels of the soils in the okra bed. If phosphorous is too low, you could supply a boost with a foliar spray or soil drench of a liquid fertilizer that is high in phosphorous. Just be careful not to supply more nitrogen if the current levels are already adequate.
One other fact I learned from my research is that you can prolong the production period of okra by cutting off about 1/3 of the plant top in late summer. This pruning allows plants to send out new growth and flower and fruit for a second time in the fall.
I hope this information is useful. You are welcome to contact our Help Desk if you have further questions.
Help Desk of the UC Master Gardener Program of Contra Costa County (TKL)
Editor's note: For more information on okra gardening, a Sonoma County MG article is recommended (click)... the pictures in this blog post came from that article.
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 (//ucanr.edu/blogs/CCMGBlog/).
Hot Days and Cold Nights:: Interpreting Chill Accumulation via the Utah Model.
Strawberries (and caneberries) rely on enough accumulation of chill to develop normally. Insufficient chill in strawberry results in lower vigor and productivity, while excessive chill can result in overly vegetative plants with again lowered productivity. This is an expansive topic, and readers can refer to other articles in this blog to familiarize themselves with the concept further.
The question we take up today is with the current spate of warm temperatures during the day in the strawberry plant production areas in Northern California, are we losing some of the accumulated chill during the night. The answer is an unequivocal “yes”.
Consider the chart below taken from the UC Davis Fruits and Nuts website which comes from the publication “Chilling Accumulation: Its Importance and Estimation” by David H. Byrne and Terry Bacon out of the Department of Horticultural Sciences at Texas A&M University:
http://fruitsandnuts.ucdavis.edu/Weather_Services/
chilling_accumulation_models/about_chilling_units/
The Byrne and Bacon explanation of calculations used by the Utah model: |
The Pomology Weather Services program calculations for the Utah model: |
1 hour below 34°F = 0.0 chill unit 1 hour 35 - 36°F = 0.5 chill units 1 hour 37 - 48°F = 1.0 chill units 1 hour 49 - 54°F = 0.5 chill units 1 hour 55 - 60°F = 0.0 chill units 1 hour 61 - 65°F = -0.5 chill units 1 hour >65°F = -1.0 chill units |
1 hour below 34°F = 0.0 chill unit 1 hour 34.01 - 36°F = 0.5 chill unit 1 hour 36.01 - 48°F = 1.0 chill unit 1 hour 48.01 - 54°F = 0.5 chill unit 1 hour 54.01 - 60°F = 0.0 chill unit 1 hour 60.01 - 65°F = -0.5 chill unit 1 hour >65.01°F = -1.0 chill unit |
Let's go to the accumulator of chill hours from Lassen Canyon Nursery to apply this to our situation today:
http://lassencanyonnursery.com/macdoel-ranch-cumulative-chilling-hours/
As of 9/22/2015, it looks like we have 32 hours (or units) below 32o F (0.0 chill units x 32 accumulated), 143 hours between 33o F and 45o F, 166 hours between 46o F and 60o F, and 177 hours over 61o F (130 from 61o F to 80o F and another 47 over 81o F). I'm assuming the interesting part of chill accumulation for Lassen is the 33o F to 45o F range, which we'll multiply by 1 for 143 chill units, then add on the less effective 46o F and 60o F of 83 chill units (166 hours x 0.5) for a total of 223 accumulated hours in Macdoel so far.
However, from this total of 223 hours accumulated we are going account for the negative effect of 177 hours over 61o F. We don't have the advantage of knowing how many hours were in the range of 60o F to 65o F for which the multiplier is only -0.5 chill units, but indulge me and let's put that amount at a quarter of the 177 hours over 61o F (177*0.25 = 44) . Meaning that (44 hours x -0.5 chill units) + (133 x -1.0 chill units) = -155 chill units.
As such, according to the Utah Model, total accumulation this year as of September 23 in Macdoel is 68 chill units (223 units - 155 units).
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Nursery plant harvest in Macdoel, 2006.
Biological Control of Fungus Gnats
[From the July 2014 issue of the UC IPM Retail Nursery & Garden Center News] Fungus gnats...