Terminology for Cranberry Bud Development and Growth (EXT)

I extracted this from this from

http://www.hort.wisc.edu/cran/mgt_articles/articles_gen_info/TerminologyCranBudDev/cranbuddev.htm

I find this article interesting because it explains the different stages of bud development.



Beth Ann A. Workmaster, Jiwan P. Palta, and Teryl R. Roper
Department of HorticultureUniversity of Wisconsin-Madison College of Agriculture and Life Sciences, Madison, WI 53706


Cranberry researchers and growers typically use some sort of ad hoc terminology to refer to the growth stages of the bud in the springtime. This can be based on measurements of the changes in size of the bud and the subsequent growth, or on a description of their physical attributes, or morphology. It would be useful to standardize this terminology to aid in communication between and among researchers and growers. We have recently begun a research program at the University of Wisconsin-Madison to study cranberry frost survival. Our goal is to better advise growers about the freezing temperatures to which the plants will survive at different times of the year.


After taking close-up photographs of the buds of the uprights for several weeks in the spring of 1995 we established a visual continuum of spring bud development and growth. As expected, bud hardiness changed dramatically over the course of the spring, from being able to withstand temperatures colder than -4°F when dormant to surviving only temperatures just below freezing after the new uprights elongate. Thus, at different points along that bud developmental continuum significant changes in hardiness occur. In order to assess these changes more specifically we have been working on developing a useful set of terminology for these different bud stages.

The terminology we propose here was developed with input from growers at the 1995 summer field day of the Wisconsin State Cranberry Growers Association and researchers at the 1995 North American Cranberry Researchers and Extension Workers Conference. Our immediate goal for this terminology is to learn more about the relationship between bud stages and frost hardiness, while our longer term goal is to facilitate discussion between and among researchers and growers.

We have chosen to focus on describing the morphological changes in bud development and growth, rather than absolute changes in bud size or stem growth. Reproductive and vegetative buds vary in size, as does the amount of stem elongation during growth. Morphological changes, such as bud swelling and flower pedicel elongation, are more indicative of development than mere increase in size and length. We present here our current terminology. Each stage is represented by one or two pictures and is described below.

1. Tight bud. This is a resting bud that has fulfilled dormancy and chilling requirements. This bud becomes active when favorable growing conditions are present. Bud scales are tightly wrapped. Bud scales are usually light or dark red, especially in the upper part of the canopy. When viewed from the side, buds are compact and nestled down into the top leaves.

2. Bud swell. This bud is no longer at rest. As bud begins to swell, bud scales are pushed outwards and have a slightly loosened appearance. Bud scale margins are more easily seen. Most buds still retain their light or dark red color.

3. Cabbagehead. Substantial swelling of the bud has occurred. Bud scales are opening, but still enclose the new growth. As the name implies, this stage is named for the bud’s ressemblance to a head of cabbage. Many buds have lost much or all of their red pigment. When viewed from the side, buds appear pointy and lengthened, in preparation for the emergence of the new growth.

4. Bud break. New growth emerges through the bud scales. The tips of uppermost new leaves are visible.

5. Bud elongation. New leaves and some flower bracts, which envelope the flower buds, emerge from the bud. All new growth is held tightly and parallel to the stem.

6. Roughneck. Stem elongates significantly. All flower buds and bracts are visible, being held tight to the stem. New leaves are still oriented parallel to the stem. Flower pedicels have not elongated.

7. Hook. Flower pedicels elongate, starting with the lowest flower buds on the upright. The flower bud droops, forming the characteristic hook shape. New leaves are becoming more perpendicular to the stem.

8. Bloom. Flowers open, starting from the lowest buds.

Fertilizer - Feeding the Soil - Part 2

by Richard Chew




I knew embarking in such a hobby, I'll need to relearn good practises and unlearn some bad ones to create a successful garden.


Well thats the reason why I am posting this Part 2 version.




As I am writing, I have started experimenting some new fertilizers to treat some special conditions on my rose plant.


I didn't know that Vermicompost fertilizer is easily available in major nursery. I bought it immediately as some of plants were in not so good shape after some continous heavy rain in September. The soil was pretty soaked with water. It is so bad that it is similar to those that is picked up from the river bank.






I replaced the soil with new ones as I didn't think the soil condition was reversible. Hopefully my rose can fully recover.

However for those that were not so critical, I tried Vermicompost as a means for preventive measures.


Vermicompost is natural and it is more simplified Nitrogen composition compares to those Organic manure. And it is very effective in binding soils in clumps to form better soil aeration and drainage.




Another thing that I add was the water soluble Miracid N30-P10-K10 fertilizer to increase the acidity of the soil because some of the roses were turning yellow, even the dainthus were turning yellow too.



After a couple of weeks of continous fertilizing, the results were quite tangible. Firstly the drainage has improved despite the continous wet weather. Secondly the top soil is more clumpy, rather than flat as flatness and compact at top soil is sign of too much water.






The leaves vein started to green.



For the healthier ones with numerous new shoots, I started with water soluble N10-P54-K10 by Shultz. I use very little about 1/4 teaspoon, but increase the frequency to 2 times a day. I started this a little too late, as some of the buds doesn't look so good. If I started earlier before the buds mature, perhaps it may produce better result.





Nevertheless it didn't look badly deformed when it bloomed. The bloom shape still intact and petals were looking good.


Just as I am posting this, I am also experimenting the effectiveness of some other fertilizer, especially for more established roses to increase the rate of vermicomposting. It should be something that is economical and at same time one that the earthworms love.







Read continuation in Part 3

Useful Tips (EXT)

I found some useful tips from Plant Answers site created by Dr Jerry Parsons.

http://plantanswers.tamu.edu/trees/rose.html


Rose

1. Q. As the weather gets hotter, my roses look worse. What can I do to insure that they survive the summer?

A. Poor cultural practices and neglect during summer months will weaken plants and make it harder for them to survive. Here are some suggestions on summer care of roses:

As flowers fade and petals fall remove old flowers. Otherwise, food and energy will go into seed production rather than plant growth and flower production.

When removing spent flowers cut just above the second five-leaflet leaf above the main cane or branch.

Use a complete fertilizer such as 10-10-5, 15-10-10 or similar formulations at the rate of 1 1/4 pounds per 100 square feet just as new growth starts in spring then apply about 1/3 to

During hot, dry weather water rose beds thoroughly every week to a depth of 8-10 inches.
Control blackspot and mildew by spraying with Benlate or Funginex every 7-10 days from the time new growth starts in the spring and continue throughout the growing season until frost.
So for optimum flower production this summer and fall give your roses that bit of added attention.

2. Q. I think my rose bushes need an overhaul - - they look terrible! Is there anyway to "supercharge" the bushes so they will bloom this fall?

A. The cooler temperatures of fall will stimulate rose bush growth and intensify the color of the rose blooms. Many people do not prepare their roses for this second spring so they miss really the most spectacular, longest lasting bloom period. Roses should be pruned and groomed from now until no later than September 20. Fall pruning is lighter than in the spring. Cut about one-fourth to one-third of the bush. When pruning miniatures, other than cleaning them out, simply cut off all the blooms. When pruning standard size roses remove all of the blooms and bloom pods. When removing the recommended one-fourth of the bush cut all canes back to pencil-size wood, remove any crossing canes which might rub and damage adjoining canes and remove any dead or diseased wood. The general shape of a rose bush should be open-centered or vase-like with canes evenly distributed around the outside. To prolong the bloom period you may want to prune only one-half of your rose bush at a time then wait a week to complete the process. The half which was pruned first will bloom first generally 45 days after pruning occurred. Mid-October should begin the peak rose bloom season. Remove and dispose of all diseased leaves with black spots on the foliage. Black spot fungus must be prevented rather than cured. Prevention is easily accomplished by a 7 - l0 day spray schedule with Funginex fungicide (Black Spot is a fungus disease) and Orthene insecticide for thrips (these cause blooms to stay closed or be mis-shapened). Spraying should continue until the first hard freeze occurs. By September, the spray interval should be shortened to every 7 days since disease is more prevalent. After fall pruning has been done, give the bushes a "shot in the arm" with the addition of fertilizer. Feeding with a water soluble fertilizer should occur every two weeks. Follow instructions by mixing one tablespoon of water soluble fertilizer per gallon of water and pour a gallon of solution around each plant. Don¹t feed with either liquid or dry fertilizers after October 15th so that growth can slow and harden for the winter cold. Water and wait for the beauty of fall - - that's all you have to do to "supercharge" your rose bushes.

3. Q. What are the best roses to grow?

A. Once you decide which rose type you want to plant (most folks will plant a hybrid tea or grandiflora), you will need to know which are the best varieties within those classifications. I not only have a listing of the best rose varieties for this area but also a POP (proof of the pudding) rating as compelled by the best rose growers in the state. Any POP rating above 8.0 is spectacular. Those rose varieties with POP above 7 are considered excellent. The best of the hybrid teas and grandifloras include:

First Prize - a pink-blend colored rose with a long pointed bud. It is a medium sized bush that is somewhat susceptible to black spot and mildew. It is, nevertheless, one of the top rated roses in the world with a POP of 9.1.

Color Magic - a pink blend rose with a "changing color" character with deeper colors of ivory to pink spreading and intensifying as petals are exposed to sunlight. The POP of Color Magic is 8.0.

Fragrant Cloud - This variety produces an orange-red bloom on a medium size bush. The bloom is extremely fragrant and Fragrant Cloud rates a POP of 8.1.

Uncle Joe (Toro)- The best of the red roses with a POP of 7.9.

Bewitched- A medium pink rose that grows on a medium sized bush. It merits a POP of 7.2.

Double Delight - A stunning rose which has a cream colored bloom with red edges. It is one of the most favored of all rose varieties and has a POP rating of 9.0.

Candlelight - A deep yellow bloom which is tinged with pink especially in the fall. Blooms are produced on a tall, vigorous plant. No POP available.

Christian Dior - A medium red bloom with an ovoid pointed bud. It has a large flower and an abundance of blooms. The POP rating is 7.1. The edges of the petals burn in hot dry settings, so it is advisable to plant where it will receive some afternoon shade.

Queen Elizabeth - This is the most popular rose of the Grandiflora class. It has a medium pink bloom, produces an abundance of blooms and rates a POP of 9.1.

White Masterpiece - Very large (up to 8 inches across), double centered white flower. It's POP is only 7.3 because of double-centered, non-displayable blooms.

Montezuma - A double, deep coral-pink colored bloom with 32-40 petals. Montezuma comes very close to the grandiflora ideal with a POP of 7.1.

Touch of Class - It is a pink blend which normally has super form. When it has been in commerce long enough to have a rating it should certainly be a POP of over 9.0.

In the floribunda category the winners are Fire King, an orange red with a POP of 7.5;

Gene Boerner, a medium pink rose that grows on a very tall and bushy plant--this variety has a POP of 8.8, one of the highest rated floribunda;

Little Darling, which would seem misnamed since it is an extremely tall and spreading bush with a profusion of yellow blend blooms of a hybrid tea form, has a POP of 8.8;

Pink Rosette is an older variety with low height and bushy pattern of growth yet it is extremely floriferous (it is not unusual for 20-25 blooms to be on one cane; and, last but not least,

Rose Parade, a pink blend bloom on a bush of medium height, has a POP of 7.7.

In the climbing rose category, the varieties Blaze (medium red), Climbing America (coral pink) and Don Juan (deep red) are recommended. Some of the best miniatures are Beauty Secret (medium red), Dreamglo (red blend), Party Girl (yellow blend), Starina (orange-red) and Starglo (white).

Miniatures have become very popular in the last few years. As a result hundreds of new cultivars have bee introduced with different results.

The top five exhibition winners in the country are Jean Kenneally, a tall apricot blend with a POP of 7.9;

Minnie Pearl, a tall and bushy plant with pink blend blooms and a POP 8.1;

Snow Bride, a medium sized white bloom with a POP of 8.0;

Party Girl, a yellow blend on a medium sized bush and a POP of 8.0;

and Little Jackie, a vigorous, tall bush that produces a light petaled, orange blend bloom. Others, in order of preference, are Rainbow's End, a yellow blend on a medium sized plant and a POP of 8.0

and Starina, a small to medium, orange red whose POP is the highest in the world at 9.6.

Two others that produce well in this climate are Kathy Robinson, a tall, bushy plant that has pink blend blooms with a POP of 8.7

and Over-The-Rainbow, a medium size plant with a bushy growth habit which produces a red blend colored rose with a POP of 8.5.

4. Q: When do you prune roses? Climbing roses?

A: Hybrid tea, Grandiflora and Floribunda roses require annual pruning in the spring just prior to bud break. If rose bushes are pruned too early, injury from late frost may make a second pruning necessary. Climbing roses should be pruned in the fall, any time after cold weather sets in. Old rambler roses should be pruned immediately after flowering.

5. Q: Leaves are eaten off my rose bush. Sometimes the whole leaf blade is gone, and other times, the leaf is half eaten. What type of insect is eating my plants?

A: Probably some type of chewing insect. Examine plants frequently to see if any pests can be found. Treatment depends on insect. Leaf cutting bees or ants are a common problem.

6. Q: Should I or could I pour pickle juice around roses?

A: Pickle juice would be acid, so it would lower the pH somewhat, but sulfur would be a better choice. You would need to know the actual pH before you did anything.

7. Q: When and how do you start rose cuttings?

A: Roses can be started from terminal cuttings or leaf bud cuttings. However, because all hybrid roses are grafted onto a common root stock you should buy the variety you want that is already grafted.

8. Q: Does the petal count of roses determine the number of days before subsequent blooms occur?

A: Yes, on hybrid teas. According to the Rose Society if a flower has forty petal blooms when cut, then it will take 40 days to rebloom. However, this is a broad rule of thumb.

9. Q: Can fish oil be used to feed roses?

A: No, not strong enough. Suggest 12-12-12 or 10-20-10.

10. Q: Do you need organic material, iron and nitrogen fertilizer for roses?

A: Needs organic material; iron is not a usual problem in most rose beds; suggest 12-12-12 or 10-20-10 fertilizer rather than straight nitrogen.

11. Q. I have heard about the great attributes of old-fashioned or antique roses. What do you know about them?

A. Though these plants do have some redeeming features, they are not what most people want in a garden rose. Many consider Belinda's Rose (Belinda's Dream) to be the best (most desirable qualities of disease resistant, fragrance, durability, flower form) rose in the world.

12. Q. I think my rose bushes need an overhaul - - they look terrible! Is there anyway to "supercharge" the bushes so they will bloom this fall?

A. The cooler temperatures of fall will stimulate rose bush growth and intensify the color of the rose blooms. Many people do not prepare their roses for this second spring so they miss really the most spectacular, longest lasting bloom period. Roses should be pruned and groomed from now until no later than September 20. Fall pruning is lighter than in the spring. Cut about one-fourth to one-third of the bush. When pruning miniatures, other than cleaning them out, simply cut off all the blooms. When pruning standard size roses remove all of the blooms and bloom pods. When removing the recommended one-fourth of the bush cut all canes back to pencil-size wood, remove any crossing canes which might rub and damage adjoining canes and remove any dead or diseased wood. The general shape of a rose bush should be open-centered or vase-like with canes evenly distributed around the outside. To prolong the bloom period you may want to prune only one-half of your rose bush at a time then wait a week to complete the process. The half which was pruned first will bloom first generally 45 days after pruning occurred. Mid-October should begin the peak rose bloom season. Remove and dispose of all diseased leaves with black spots on the foliage. Black spot fungus must be prevented rather than cured. Prevention is easily accomplished by a 7-10 day spray schedule with Funginex fungicide (Black Spot is a fungus disease) and Orthene insecticide for thrips (these cause blooms to stay closed or be mis-shapened). Spraying should continue until the first hard freeze occurs. By September, the spray interval should be shortened to every 7 days since disease is more prevalent. After fall pruning has been done, give the bushes a "shot in the arm" with the addition of fertilizer. Feeding with a water soluble fertilizer should occur every two weeks. Follow instructions by mixing one tablespoon of water soluble fertilizer per gallon of water and pour a gallon of solution around each plant Don't feed with either liquid or dry fertilizers after October 15th so that growth can slow and harden for the winter cold. Water and wait for the beauty of fall - - that's all you have to do to "supercharge" your rose bushes.

13. Q. I have weird looking leaves on the growing tips of my rose bushes. The affected leaves have a whitish-grayish, dust- like substance on them. What is causing this problem and how can I solve it?

A. You have a BIG problem but a common one. Pest control is one of the major problems facing area rose growers. Insects such as thrips damage flower buds and cause them not to open or to form odd-shaped blooms. These insects must be prevented rather than waiting until damage occurs before acting. Once damaged, blooms are not salvageable. The same is true for foliage diseases--prevention rather than cure should be the rule. The most notorious of the rose foliage diseases are black spot and powdery mildew, which can severely damage most of leaves and impair the plant's ability to produce a bounty of large, beautiful blooms. The black spot fungus disease is prevented by applying triforine (Ortho Funginex) or benomyl (Greenlight Systemic Fungicide) spray every 7-10 days. Powdery mildew, the affliction which you describe as affecting your roses, is best controlled with bayleton (Greenlight Fung-Away) or benomyl (Greenlight Systemic Fungicide). Apply Orthene, diazinon or malathion for insect control when necessary. Do not apply a mixture of Orthene and Funginex more than two weeks in a row. Applying insecticides and fungicides separately is safer for plant health. Also, using insecticide on the buds only, rather than the entire bush, gets super results for insect control. These pesticide sprays are a necessity if rose growers expect an abundance of perfect blooms on disease-free plants.

14. Q. My 22 hybrid tea roses and five climbing roses have been damaged by a late freeze. The new green growth, leaves about three inches, have turned brown and some of the canes on the hybrid teas are black and soft. In 12 years of growing rosese I have not experienced any damage this severe. Should I remove the brown leaves and blackened canes now or wait until warmer weather? Should I fertilize to encourage new growth now or wait until new growth appears on it's on, hopefully they are not dead. What setbacks am I to expect?

A: Wait until the plants recover and begin a new flush of growth -- then cut all dead wood above the flushing area. If you want to do something now, it is a safe bet to remove blackened, withered wood. However, some buds may be damaged, even on green wood, to a point they will not initiate foliage. BEWARE that you don't forget most roses are grafted so if sprouts and shoots arise only from beneath the graft union, you have lost the rose. I would wait on fertilization until after the sprouting has begun then feed as you would normally.

15. Q. I have a Fragrant Cloud rose that has white spots covering the older canes, and it has spread to some of the leaves. The smaller canes have turned brown and died back. The spots are not moving (not bugs). Any clues?

A: You are dealing with "critters" on your Fragrant Cloud (GOOD CHOICE!!) rose called scale. They are aphid-like covered with a white sheild. When you prune next February, try to remove all affected branches. If you just have one bush, you can rub all you see off with your hand. You can direct spray them with an insecticide such as Orthene or direct spray with a summer oil spray. BE SURE to be careful and FOLLOW label instructions with the summer oil spray or you can damage your plant to the point of death. Roses are having a hard time with these hot temperatures but summer prune them in September for beautiful fall bloom in cool temperatures.

16. Q: Could you please enlighten me on the history of the yellow rose of texas?

A: The "Yellow Rose of Texas" according to the history was NOT a flower but a lady-of-the-night who kept Santa Anna "occupied" to delay battle so that reinforcements could arise. Ironically, the yellow rose is the weakest of all rose colors -- horticulturists and rose breeders are constantly trying to find a good, yellow rose. In Dr. William Welch's book, Antique Roses For the South, he indicates that "Pioneers moving westward often took 'Harrison's Yellow' with them, and it persists in old California gardens today, testifying to the transcontinental trek to new frontiers. Some historians consider 'Harrison's Yellow' to be the "Yellow Rose of Texas".

October Bloom

By Richard Chew

Below are the rewards in October.

I haven't found the name of the rose, but will try to identify them soon.

I got this rose for almost a month, and I am glad to get about 4 blooms and about 7 buds ready to bloom in the next 2 weeks. The diameter when it is fully opened is about 5cm. Colour is fuchsia.

This shot was taken under strong morning sun.


This was taken under shaded light.


Below is a double delight. Though it was quite in bad condition, managed to recover it and was rewarded with 1 bloom. I am supposed to remove the bud so that more energy is channeled to grow healthier foliage and buds but I thought no need to rush, let nature takes its course.

Below is my new addition to my garden in Oct. I didn't expect it to be so bushy. And new buds keep coming up. Currently there is only 1 strong stem with many small ones from the base.

The next thing to do is to peg down the stronger stems and hope more stronger shoots to form fuller and more balanced bush.

Fully opened diameter is about 3 cm. Its blooms produces a strong dark pink colour, and as it matures it gradually fades to lighter tone.

Come visit again in end November to see my newer additions. Hopefully by then will have more showy flowers.

Photosynthesis - How many hours of sunlight does your rose need?

by Richard Chew


How many hours of direct sunlight does the roses require? This is the most common question. I asked the same question when I started growing roses.


After doing some research on plant psychology, I learned that ensuring the minimum hours of indirect sunlight is as important as determining the minimum direct sunlight. The reason is in Malaysia we are blessed with long hours of sunlight, having direct sunlight is not so crucial.


Before we determine the number of hours of sunlight for our roses, we need to understand how and what is the optimum rate of photosynthesis.

A commonly used slightly simplified equation for photosynthesis is:

6 CO2(g) + 12 H2O(l) + photons → C6H12O6(aq) + 6 O2(g) + 6 H2O(l)

carbon dioxide + water + light energy → glucose + oxygen + water

The equation is often presented in introductory chemistry texts in an even more simplified form as:

6 CO2(g) + 6 H2O(l) + photons → C6H12O6(aq) + 6 O2(g)

What this means is that during photosynthesis, the plant will use light energy to manufacture glucose. At the end of this process, glucose is stored for the purpose of plant growth and production of carbohydrate.

2 H2O + 2 NADP+ + 2 ADP + 2 Pi + light → 2 NADPH + 2 H+ + 2 ATP + O2

While knowing photosynthesis is at work during sunlight, there is another process that is at work all the time. This process is known to be light-independent process. That means during night or darkness, the plant will draw energy stored to use CO2 for the production of carbohydrate.

3 CO2 + 9 ATP + 6 NADPH + 6 H+ → C3H6O3-phosphate + 9 ADP + 8 Pi + 6 NADP+ + 3 H2O

This process of respiration happens all day and night.

Another critical factor to take note is that when sun light is very intensed and temperatures rises, photosynthesis rate shall decline. However respiration rate will continue to rise, therefore reduces the net photosynthesis (lower photorespiration - in shaded red below).

Therefore understanding this effect is important to determine the right amount of direct sunlight and at which of part of the day is crucial, especially trying to grow roses in tropical country like Malaysia. As Malaysia weather is known to have average of 32 to 33 degress C outdoors, it is crucial not to over exposed the roses with too much heat. It doesn't harm that much if its for short period, as roses are known to be quite tolerant of direct sun.

I would prefer to place roses at a location where it can draw direct morning sun for about 2 to 4 hours as temperature is at lowest of the day, and indirect sunlight for 5 to 7 hours. The rose plant must get indirect sunlight from opened sky and not from opened window (or any location that is shielded, it can never grow indoor). In such condition, you provide a controlled temperature environment within 28 to 32 degress C.

A practical way to artificially create this effect is by growing roses next to a wall or a taller tree/plant that will shield your roses from the intensed afternoon sun.

How much light does my roses get?

My garden usually gets direct sun between 10am to 12pm, my estimation is about 100,000 lux (light intensity) at clear sky. It is believed that at this light intensity, photosynthesis will reach light saturation (photosynthesis will cease if reach light saturation of 32,000 lux for upper leave and 100,000 lux for whole plant)

Thankfully Malaysia's weather is usually cloudy, therefore will diffuse the direct sunlight. However it is necessary to take pre-caution if weather is dry and hot for long periods as the plant will be exposed to high temperature thus raise the rate of respiration. That is why, I feel it is necessary to place roses at location that is shielded from hot afternoon sun, but not totally shielded from indirect sun.

Just to ensure that your roses receives sufficient sunlight, especially if your garden has limited space and suspicion of insufficient light, just do a simple calculation.

8am to 5pm - 9 hours x 30,000 lux (indirect sunlight) = 270,000 lux hours

10am to 12pm - 2 hours x 100,000 lux (direct sunlight) x 30% (below upper leave) = 60,000 lux hours

Total is 330,000 lux hours.

In case you are unsure how many lux (light intensity) in your garden, in general you can use 100,000 lux for direct sunlight, 30,000 for indirect sunlight and 5,000 for low light (indoor light. You will need to multiply the ratio of 0.3 (30%) for direct sunlight, as only the leaves below the upper leave will benefit from the sunlight. It is believed that at high intensity the upper leaves will cease photosynthesis due to higher light saturation.

For the plant to survive it requires a minimum of 160,000 lux hours of sun light.

If your light calculation exceeds the minimum of 160,000, your rose should thrive. If you have read some books on rose growing, you may notice that most say that roses require direct sunlight, that is because the weather is different from our tropical weather in Malaysia. Averagely Malaysia outdoor weather is at 32 degrees C, if at direct sunlight, the temperature may increase for another 2 to 3 degrees C, which lower the net photorespiration rate.

Also if the heat reaches the soil, the good bacterias in the soil will also cease their activities thus will affect the plant in the long run. It won't do much harm if exposed for short periods, as it reduces the risk of fungal infections. But if for long periods, the plant roots will deplete in its nutrition as the bacterias stop breaking down the nitrogen components.

You may want to check the earlier posting that is extracted from external site. I posted in this blog, in case you wish to know about plant leaves anatomy, photosynthesis and light.

http://rosegrowing.blogspot.com/2008/10/chemistry-in-shadehouses-ext.html

http://rosegrowing.blogspot.com/2008/10/photosynthesis-leaves-light-ext.html

This posting explains the impact of diffuse light on photosynthesis rate. It dispel the myths of having direct sunlight leads to increased in photosynthesis rate.

http://rosegrowing.blogspot.com/2008/10/large-volcanic-eruptions-help-plants.html