Aphids on Napa Cabbage

My battle with pests continues.  When I thought the cabbage worms on the kale have been eradicated, I found another colony of insurgents on the underside of the Napa cabbage leaves -- Aphids!  What looked like soil particles are pests sucking the life out of my plants.  Aphids are very tiny insects but they are not to be taken for granted because of their ability multiply at an alarming rate.

Aphids are parthenogenetic.  They have the ability to reproduce asexually.  They can reproduce without mating - giving birth to multiple live offspring in a day (1).  Not all of theme  have wings but they have some allies - the ants - that can move them from one place to another better place.

So what do you do when you find out that your young plants are infested with aphids?  When it comes to my kitchen garden I resist the temptation to spray anything store-bought for as long as possible.  In other words, pesticides are my last recourse.   At the first sign of infestation, aphid colonies can be easily disrupted by spraying them off with water.  Repeat daily until they are gone maybe about three to four days depending on how severe the infestation.  If you think they are beyond water-treatment, I would use Neem Oil or other plant-based pesticides.

In addition to this, there are also beneficial insects that are naturally around your garden such as ladybugs (Coccinella septempunctata) and lacewings (Chrysoperla rufilabris).  To increase their population in your garden you can buy them from your local nursery and let them out where the problem is most severe.

After all the secret is not in the toxicity level of the pesticide but the conscientiousness of the gardener in regularly inspecting the garden.  When the problem is caught early, it is manageable.

Stroll in your garden.  

It is good for you and your plants.  :)

__________
1 Integrated Pest Management (UC)

October Already?

The day is mild and almost cool.  Most leaves are grayish green from the accumulation of dust.  For some plants new leaves are emerging, flowers are blooming again and the grass is once more putting on a sharper tint of green - as if they did not get the memo. This is October in California!

Apple of unknown variety.  I'm guessing it is Gala

It is hard to believe we are starting the last quarter of the year.  To me it seems like only last month when the apple blossoms were just starting to open.  Now the air is filled with the fruity smells of apples and apple pies.  Autumn in our area happens gradually.  Here are some pictures from my garden on this first day of October:

Quail and Basil sitting on a patio table.

Abutilon 'Tiger Eye' is beginning to bloom again.

Kalanchoe luciae ''Flapjack' seems to appreciate cooler temperatures.

We attract birds into our garden - they are interesting and are effective pest control.

Hydrangea:  Regardless of the color, the flowers usually turn burgundy in the fall. 

October is the second spring of the year!

Cabbage-worm on Kale

Cabbage Worm (Pieris rapae) on kale.

The leaves of my kale and broccoli are disappearing.  I thought that they were being eaten by some earwigs but upon close inspection I saw a multitude of velvety green larvae that are camouflaged on the leaves.  These are the larvae of the adult moth Pieris rapae. 

Pieris rapae is a beautiful small-sized butterfly known as the Cabbage White butterfly.  If you see a dainty-looking white butterfly with black dots on the wings flying around your garden, be extra observant.  While the adult is harmless, the larvae (commonly known as Cabbage-worm) are voracious and they feed on most brassica crops. At the early stages of the larvae, the damage happens slowly but once they reach a substantial size, they can defoliate the plants quickly.

There are a number of effective and safe biological control for the cabbage worm.  Basillus thuringiensis (Bt) and spinosad.  Ask your local nursery for these active ingredients and they will lead you to the right products.  These are both biological and considered organic pesticides.

As for me, since I do not have a huge garden, I prefer to do it by hand - picking the worms every morning. This is also biological and organic method, mind you. :) But this requires that I have to be vigilant.  

Stroll in your garden, and squash all the cabbage-worms you see :)

Fall is Here

Pomegranate  (Punica grantum 'Wonderful')

First day of fall.  The temperature dropped about ten degrees (F) since yesterday and a few drops - literally few drops - of rain fell on the ground.  But in this part of California, any amount of precipitation is appreciated.

And what better picture to mark the beginning of the season than the pomegranate fruits that are getting plump and turning red.  Although there are other fruits such as figs, apples and even pears that are too high even with my fruit picker still remaining, they all are all winding up.  

Pomegranate  tree in a pot.

"No man can taste the fruits of autumn while he is delighting his scent with the flowers of spring." ~ Samuel Johnson

Poppies

Poppies

Poppies always fascinate me. 

Stilted on long skinny stalks, they dance to the slightest wind. 

Delicate yet intensely colored petals wave at me

Drawing my eyes to the unopened buds

Demure and tender, they are blanketed in trichomes 

Carefully they peep through a slit making sure the sun is out...

And like parasols they unfurl to add color to the field

As they join in the dance.

Happy are the fields where poppies dance.

~~~

There are no poppies in my garden but if I could command any plant to do something I would say to the poppy to grow beautifully in my garden.   But because I cannot do that, I drew poppies instead. This is my first attempt to sketch poppies.  Someday I might sketch a more realistic version of this subject. :) 

Blossom End-Rot: Not All Tomatoes Were Created Equal

One obvious observation in my garden this season is the susceptibility of 'San Marzano' tomato to blossom-end-rot.  All the fruits harvested so far have the distinguishing ugly black spot on the far end.

Blossom-end-rot is caused by lack of available soil moisture.  It is a common knowledge that blossom end-rot is a calcium deficiency symptom.  But I say that in this area (Zone 9), it is more of water stress damage.  I have noticed that symptoms always show up few days after plants experienced water stress.  The obvious indicators of water stress is wilting.  Such wilting is often unavoidable during periods of hot days, as in 100-108 (F) days that we had last week, when the rate of transpiration is greater than the rate of water uptake.  As the temperatures soar above a certain level, C3 plants like tomatoes will automatically close their stomata to avoid further water loss.  This phenomenon halts transpiration which also halts water absorption by the roots.  Imagine a micro-siphon that starts from the tips of the roots and ending at the stomata on the leave surface - that is the xylem that carries water and nutrients (including calcium) to the different parts of the plant. Nutrient-carrying water passes through this siphon constantly except when there is no water available within the root zone that result in the closing of the outlet (stomata).  In other words, when the plant is wilted, the passage of water has been closed.  No matter how much calcium is in the soil, when  water is not running through the xylem, calcium will be limited in the plant. Calcium is needed in the formation of cell membranes. When the plant is deficient in calcium, the membranes on the furthest end of the fruits break down. Hence, the blackened spot.

Because different varieties respond differently to water stress, they also differ in their susceptibility to blossom end rot.  This season I grew two varieties of tomatoes side by side in the same growing conditions.  While the fruits of 'Pink Brandywine'were all beautiful and blemish-free, the fruits of San Marzano showed blossom-end-rot.  So I might just plant 'Pink Brandywine' in the future.  If I were to grow San Marzano again, I would have to change some of the growing techniques in order to get better fruits:

1.  Mulch.  Not just mulch but thick mulch and compost around the base of the plants.  Refresh mulch in June as the temperature begins to get really hot.

2.  Automatically irrigate.  One day of skipped watering during hot days will cause damage on the fruits.  Increase irrigation time during the month of June all the way to July.

3.  Apply fertilizer only in low doses.  The salts in fertilizers compete with the plants for water.

4.  Choose an area that gets morning sun and afternoon shade for tomatoes.

When choosing tomato varieties, consider their resistance to blossom-end-rot.

Strawberries: Understanding the Effects of Photoperiod and Temperature

Have you ever wondered why some strawberries bear fruits earlier than others?  Have you ever wondered why some strawberries bear fruits longer than other ones?  Or for that matter, have you ever wondered why some plants flower only at specific times of the year?  

Definitions

Before we answer these questions, here are three terms we need to define for ease of understanding:

1. Photoperiod or Daylength is the number of hours of daylight during a 24-hr period.

2. Flower Initiation - is the beginning of reproductive phase in plants which is triggered by biochemical and hormonal changes in the plant.  For us gardeners, we would see this phenomenon later when visual indicators are met - flowers are out.  

3. Remotancy is the ability of a plant to bloom repeatedly throughout the growing season.  This is an important characteristics for flowering well as fruiting perennials because it prolongs the productivity of the plants. 

Photoperiod and Flowering

It has long been established in plant science that flower initiation is influenced by photoperiod. Extensive research has been done to show chemical and hormonal changes that correspond to varying photoperiods.  Shifts in hormone levels induced by photoperiod either lead to initiation or inhibition of flowering depending on the genetics of plants.  Angiosperms - flowering plant species - have been classified into three categories based on their response to daylength as follows:

     Short-day (SD) plants are those that bloom only when the daylength is less than twelve hours.

     Long-day (LD) plants are those that bloom only when the daylength is more than twelve hours.

     Day-Neutral (DN) plants are those that can bloom regardless of the daylength.

Strawberry Varieties and their Response to Photoperiod

Strawberry is one example of a plant that is responsive to photoperiod. which plays a significant role in its flower initiation as well as remotancy.  Strawberry varieties are classified according to their flowering response to this factor.  

June-bearing varieties - SD strawberries.   These are recommended for canning purposes because they yield a heavy crop in the summer.  They are the varieties that are generally grown commercially. June-bearing varieties bloom in spring when the days the less than 12 hours and warm enough for plants to grow at a reasonable rate.  In the fall when the days get below 12 hours of daylight, they undergo flower initiation again.

Ever-bearing varieties are LD strawberries.  These varieties start to bloom late in April when the daylength exceeds 12 hours and all the way to autumn when daylength shortens to under 12 hours again. Ever-bearing strawberries are recommended for a kitchen garden where fresh strawberries every now and then is desired.

Day-Neutral strawberries are those that are not significantly affected by photoperiod.  They bloom regardless of the photoperiod as long as other factors are favorable for growth.

Temperature and Fruit Setting 
Can we then say that strawberries will always bear fruit when the right photoperiod is achieved?  The answer is no.  The story is not that simple. The effect photoperiod on flowering assumes optimum temperatures.  After flower initiation occurs, temperature comes in and plays a significant role in the development of the flowers into a fruit.

In our area (Zone 9), June-bearing varieties, can start to show flowers as early as February but such flowers fail to develop into fruits because the temperatures are too cold for fruiting.  Similarly in the fall flowering is triggered again by the shorter photoperiod but such flowers fail to develop due to low temperatures.  The reason for the characteristic heavy crop from June-bearing strawberries is the favorable temperatures in the spring to early summer for fruit formation.

For ever-bearing varieties, we would expect that once the photoperiod is long enough that they would continue to produce fruits all summer long.  Not again.  Because they bloom later in the season, high temperatures (Zone 9) limit fruit development. Studies have shown that although flower initiation occurs under high temperatures on ever-bearing varieties, the percentage of fruit formed over  the number of flowers is significantly reduced (1). This is the very reason for the characteristic continuous fruiting with relatively low yields on ever-bearing varieties.  In spite of their remotancy, only few flowers successfully develop into fruits.

Photoperiod determines flower initiation; temperature determines the development of the strawberry fruit, but the behavior of the plant is determined by genetics.