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.

Helleborus vesicarius

Helleborus vesicarius  - Pencil Sketch* 

*This picture is based from a botanical sketch by Helen Campbell as published in the English Garden magazine (May 2016).  Although I haven't drawn anything before other than stick figures and circles, learning to draw is my new hobby.  And what better subject than plants? 

Helleborus vesicarius is considered a rare plant that grows on a certain mountain region that extends from Turkey to Syria and Lebanon.  It is highly toxic which explains why it can survive on hillsides where goats graze.  Unlike the more common helleborus with gorgeous flowers, the balloon-like seedpods of Helleborus vesicarius is the most notable feature in this plant.  I can only imagine that as the seedpods mature and break off from the plant that they would move around in the landscape easily with the wind.  So the balloon-like characteristic of the pod is just another seed dispersal mechanism in nature.

Draw a plant you have not seen before 

and learn something about it.

Hort Art - Photographic Impressionism

"Blue Brodiaea Breaking Through"

So my older daughter has been helping me play with some artistic tools on Photoshop lately.  Here are some of my first attempts so far using the blurr filter.  It is fun because I can hide the less important parts of the picture.  Some might call it cheating but I call it art - Hort Art.  Someday I might learn to use a drawing tablet to have a finer and better control of the cursor.

"Eden Through the Mist"

When a gardener learns a new software - art is born. :)