Wednesday, May 25, 2016

How long will Passionfruit Vines live?

The passionfruit vine, or Lilikoi, as it is known on the Hawaiian Islands, is a relatively short lived plant. Some vines may produce for only 3-4 years, while others can last a decade. They will generally not die outright, but rather the yields will begin to decline.

Commercial growers should keep harvest records, and when yields begin to drop, replanting is necessary. Backyard growers don’t have to be so quick to pull the plants since tolerate less fruit is more tolerable. I have a vine that’s reaching the decade point and is producing quite well. Since I don’t keep records though, I can’t tell if my yields are down.
Commercial strawberry growers have a similar situation. In the Southern US, plants remain in the ground for 3 or 4 years. After each season though, yields decline as the population of pathogenic organisms, such as nematodes and a variety of fungi, increase and attack the roots. In contrast, California strawberry growers remove the plants, fumigate the soil and replant each year. Because of this practice, yields remain high each year.

Wednesday, May 11, 2016

Poor Germination?

I planted some seeds and only a few came up.  
Several elements are essential for seeds to germinate.  Water is, of course, number one.  But seeds must also have an adequate supply of light, oxygen and the proper temperature range. In a few cases seed need darkness to germinate. Seeds can be buried too deep, or too close to the surface where birds or wind may carry them away. This is often true of carrot seeds.  Furthermore, the possibility of disease, fungi and bacteria, in the ground can rot the newly planted seeds.  

Some seeds need special care. Certain ones have seed coats which are extremely thick. Particular care must be taken with these in order for the water to penetrate that coat. Soaking in warm water is one means. Seeds such as lupine, locust (Robinia) and others need to be scarified, which means they need to be mechanically scratched in order for the water to penetrate. This may be done with common instruments like sandpaper or a file. Soaking in hot water is another means of scarification. Still other seeds will not germinate, or break dormancy, unless they are exposed to a period of low temperatures and moist conditions. Certain seeds germinate only after a fire. Not all seeds are created equal.

Storing Seed
Store dry, clean seeds in an airtight container marked with their name and date saved.  Store around 40 degrees F with low humidity.  The refrigerator is a good place for this. Seeds of many plants remain viable for up to 5 years, if properly stored. Some plants like delphinium, onion and parsley, produce seeds that must germinate immediately after they ripen or they lose their viability.
If you have old seeds, or seeds of questionable viability, place some of them between a paper towel that is kept constantly moist and between 65 and 70 degrees F.  Check daily for germination.  If the rate is poor, consider buying new seeds.

Sunday, April 24, 2016

Pesticides Leftover

Often times gardeners will  mix up an insecticide spray and store any leftovers for the next application.  But is it still good?  Maybe.  Mixed pesticides lose effectiveness depending on their type and the time stored. When powdered pesticides are kept dry and sealed, they can last for quite some time; the same is true for liquid formulations. But once they are mixed with water the solution may quickly lose it's potency.  

 It is the pH level of the water used in the spray mix that influences the chemical breakdown of many pesticides. The pH of a liquid is the measurement (ranging from 0 – 14) of its acidity or alkalinity. Seven is neutral, above 7 is alkaline and below 7 is acidic. Some insecticides, particularly the groups known as carbamates and organophosphates, undergo a chemical reaction in the presence of alkaline water. The reaction is known as alkaline hydrolysis, and reduces the effectiveness of the pesticide’s active ingredient. 

The chemical breakdown of a pesticide is commonly referred to in terms of its half-life. A half-life is the period of time it takes for one-half of the amount of pesticide in the water to degrade. A common insecticide, sevin, has a half life of 100-150 day in solutions whose pH is at 6. That number rapidly decreases to 24-30 days at a pH of 7. At a highly alkaline solution of 9, its half life is only 1-3 days.  Malathion’s half life goes from 8 days to 19 hours as the pH shifts from 6 to 8. One of our old fungicides, captan, last about 8 hours at neutral (7), and only 2 minutes when the spray solution is at a pH of 9.  When mixed pesticide solutions are stored for days, weeks or months, their effectiveness can greatly diminish.