Tuesday, June 28, 2016

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.

Sunday, May 22, 2016

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.

Thursday, May 19, 2016

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. :)

Sunday, May 1, 2016

Hummingbirds and Succulent Flowers

Hummingbirds are attracted to aloe vera flowers

Hummingbirds love the flowers of succulents.  Alright, maybe they don't love the flower per se but the nectar is like a special treat for them.  It has been my observation that they would check on these flowers way before they open.  Once the tubular flowers crack slightly the birds begin to stake their claim.  Any other hummingbird trying to intrude on well defended flowers, would soon find out that it was not a good idea.  


Hummingbirds will linger where there are plenty of food.

Fortunately for the resident hummingbirds, we have many different succulents in the yard -- that is in addition to three hummingbird feeders. Different succulent species bloom at different times which prolongs the season for nectar harvest for these birds.  Earlier this year some of the aeoniums and echeverias opened up.  At this time the aloe veras are in bloom. 

Hummingbirds always return to their favorite flower.

If you want to attract these beautiful creatures in your yard, plant something they like.  There are many plants that are known to attract hummingbirds, but one thing is true - succulent are among the easiest to grow. 

Entice the hummingbirds to stay in your garden - plant succulents.

Thursday, April 21, 2016

Epiphyllum

Fig. 1     Epiphyllum trained on a grape vine

This month is show time for one of my cactus orchid (epiphyllum).  Last year I trained the orange one to climb on one of the grapes.  The position is good because it is near my kitchen window and when summer comes, the grape leaves will provide shade for this forest-loving plant.  As a result - I must say, it's a lot easier to appreciate and take pictures of the flowers when they are at eye-level (Fig.1).

Fig. 2   Best pictures are taken on an overcast or rainy day.

These plants are very colorful when they bloom.  Flowers come in neon colors, it is so difficult to take good pictures under on a clear day because they are like light in themselves.  I was lucky this year because when we had several overcast days around their blooming period.

So what do we know about epiphyllum?  If you are familiar with Schlumbergera (Christmas Cactus), then you understand a lot of epiphyllum.

As an epiphyte it is like an orchid and other aerial plants. They can grow on other plants such as trees that are strong enough to support their weight.  As lithophytes they can also grow on rock crevices where they feed on decomposing leaves and roots - just like other forms of orchids.   Epiphyllums are generally of tropical origin and therefore the abundance of rain and atmospheric moisture allow these plants to survive without the roots touching the ground.  When they are grown in drier areas like our place, they need to be provided with more water to compensate for the lack of humidity.

Fig. 3    Areole:  a distinguishing characteristic of a cactus.

Epiphyllums belong in the cactus family.  They exhibit the characteristic spines called areoles (Fig. 3). Areole is a specialized branch where a flower originates.  Unlike on some of the more known cacti, the areoles on the epiphyllums are not very conspicuous but when handling the stems you would be notified of their presence in a not-so-pleasant way. The plants have flat succulent leaves that act as water storage - which is another survival mechanism for aerial plants.  In their domesticated life, this feature makes them a good low-maintenance and low-water plant - desirable in a busy world.

In my garden, these plants do not get as much care as I would like them to. There are times when the plants look shriveled due to prolonged dry condition. The good thing is that they don't die easily. I think it would take a year of no water before they finally die :)  They respond positively to a low dose of complete fertilizer.  They are also prone to snail damage.  To keep the plants looking perfect (if there is such a thing), a regular sprinkling of snail bait is necessary.

Fig. 4   The smaller buds on the left were aborted.

I also noticed that not all flower buds have a chance to open - some of them gets aborted (Fig 4). At this point I don't know what causes it.  I will do some literature review and find out what factors contribute to the unsuccessful flower formation.

Try a new plant in your garden this year, 
you might end up liking it.

Thursday, March 31, 2016

Have You Really Seen a Fig Flower?

Fig. 1    Parts of a Fig Branch.

One of the trick questions that I like to ask people regarding fig plants is: Have you ever seen a fig flower? The response I get is usually a quizzical look.  Of course! Why ask the question?  Doesn't everyone know?   

If you are looking for colorful petals where bees and butterflies land to get nectar and pollen then you are wasting your time.  The fig is different from most plants in that it produces a syconium.  The flowers are hidden inside and can only be seen by a special wasp that can enter the fruit through the ostiole (Fig. 2).  When the fruit starts to develop we only see the ovary as a syconium wall where all multiple flowers are fused together (Fig. 3). The flowers are facing inside - a characteristic of syconiun.  Imagine a fussy sock with a very tiny opening that is turned inside out.  That is how fig flowers are.  The pollination happens inside with the aid of a tiny fig wasp.  What happens to the wasp is another story. :)


Fig 2     The Ostiole: the entrance for the wasp.


Fig. 3     Cross-section of the fig syconium


Several years ago my fascination about the fig plant and it's fruit led me to write about it and buy my own fig trees.  Because of the uniqueness of the fig, even after so many years, I still am intrigued by it.  And with my own fig plants being close view from my kitchen, the scrutiny is even more intense.
So I thought that figs just bear fruits and we harvest them as they mature.  But recently I read some literature that a normal fig plant bears three crops of syconia in a given year.   And each crop has a name of its own.

Types of Syconia

1.   Mamme - .  These are the fruits remaining on the tree after the leaves have fallen off late in the fall and over winters in the tree and ripen in spring (Fig. 4).
2.  Profichi - .  These are the fruits that develop in early spring and ripen in early summer (Fig. 5).
3.   Mammoni - These are the second wave of edible fruits of the year which ripen in fall.
  

Fig. 4       Mamme:  The fruits that over winter on the tree


Fig. 5     Profichi. The first new fruits of the year


Every plant holds a mystery that awaits discovery.

Wednesday, March 9, 2016

Gardening Begins Again



It’s been raining a lot this week!  With the temperature warming up at the same time, plants are rushing to come back from their winter break.  Leaves are rapidly growing - changing the gray landscape to vibrant green once again.   Life is back!  For the angiosperms – also known as flowering plants - it’s show time! 

But while we watch the rebirth in plants, it is also time consider the work that needs to be done at this time in the garden in order to prolong the show that just begun.   Here’s my to-do-list of activities this month.  It’s kind of short because I will be on vacation for a few days – this is realistic and doable.


Activities for March

Replenish soil nutrients   An application of balanced fertilizer such as 15-15-15, 16-16-16, 10-10-10, or even the organic version 5-5-5 to perennial plants, shrubs and trees, groundcover and lawn is a good thing to do at this time.

Increase soil organic matter content A distinguishing characteristic of a poor soil is low in organic matter.  Invest in good compost (including decomposed animal manure) to apply throughout the cultivated areas of your garden every year.   You can either purchase or make your own compost.  If you have not done composting before, this is a good time to try it. 

Pull out weeds.   Pull them out when you see them.  There is no better time to control weeds other than before they use up some resources meant for your plant and before they produce seeds. 

Check irrigation system.   Make sure the system is working before we need to turn them on again.  In this area, where we do not have the luxury of regular rainfall, irrigation system is the lifeline of the garden during late spring all the way to fall.  In addition to that, we want to continue to consciously conserve and use water efficiently.   Drought might be over for a while but we need to get into the habit of conserving our natural resources.

Plant annuals In my case I’m planting some vegetables such as radishes (‘French Breakfast’ and ‘Cherry Belle’), chard, and Mexican Sunflower (Tithonia Torch).   I intend to plant other warm-season veggies but not yet.  However, if you want to harvest tomatoes early, you can plant them now – make sure to protect them from late frost.  The problem with planting too early is that they sit there in the garden without showing any significant growth for a long time and that only prolongs their  exposure to pests while they’re vulnerable.

Clean and Fertilize Plants in Containers  Remove all dead stems and leaves.  Prune if necessary.   Apply a side-dressing of fresh potting soil with a little bit of complete fertilizer to boost initial growth.  Apply another dose of complete fertilizer again after the first month of growth. 


Stroll in your garden...it's good for you.
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