The chrysanthemum is a short-day plant. That means it will set buds only after the days begin to shorten.
That, in turn, means its flowers will not be ordinarily mature until autumn.
And this means that in many cases, frost will destroy the flowers or even prevent there from being any flowers at all. This last is especially true of many of the finer mum varieties.
Use The Shading Technique For A Great Bloom
Commercial growers artificially shorten the day’s length to make chrysanthemums set their buds and develop their flowers earlier.
They do this by covering the plants with a light-proof material several hours before darkness in the evening arid, allowing it to remain in place for several hours after daylight the following day.
This shading is done every day for specific lengths of time, depending upon the variety and the date flowers are wanted.
This means varieties that normally bloom in late October and early November can be made to flower in September and even in late August.
A large part of the chrysanthemums sold by the florists through September is grown outdoors using this shading technique.
If commercial growers can profitably grow these varieties outdoors under shade, there is no reason why the amateur chrysanthemum enthusiast cannot do so too.
As it happens, it is among the late October and November varieties that the wide range of flower size and form is to be found, which sets the chrysanthemum off all other flowers.
Combine With Time-Pinching
Another advantage of shading is that the blooming time may be more closely regulated.
This is especially true if shading is combined with time-pinching.
Accurate timing is crucial to anyone interested in exhibiting at a specified date.
“Pinching,” of course, simply means removing the top of a plant in its early stage to make it branch out or otherwise regulate its growth.
“Time-pinching” is merely pinching a certain number of days in advance of the time when flowers are wanted.
Actually, the time of pinching tends to determine when the buds will be formed, which tends to determine when the flowers will open.
In time-pinching for large, high-quality blooms, the plants are pinched only once, and this is done on the exact date that has been found best for the variety in question.
Authorities differ somewhat on the optimum length of time, but, in general, when time-pinching is combined with shading, it can be recommended that plants be pinched 37 days before shading is begun.
This will work satisfactorily with any variety, though changes may be in order as experience grows.
Only three of the branches that result from the pinch should be retained if good sprays of flowers are wanted, and all other branches should be removed.
The large incurved varieties will produce excellent flowers if two stems are retained and even larger and finer blooms if only one stem is saved.
Whether one, two, or three branches are saved, the plant should be pinched precisely on the specified date.
Plants grown to no more than three stems may be set 10″ inches apart in each direction.
If bushy plants with a mass of bloom are desired rather than a large individual bloom, plants may be pinched 3 times.
In this case, the pinching is done at three-week intervals, and the last pinch is made on the day that shading starts.
For this purpose, the plants should be set 16″ inches or, better still, 18″ inches apart in each direction.
How To Shade Mums?
Although the shading of mums is somewhat exacting, it is nevertheless quite a simple procedure.
A framework of wood or wire, high enough to be well above the tops of the plants, is erected over the plot where the mums are planted, and on this framework is placed the light-proof material that will completely enclose the plants.
The covering is put on at 5 p.m. and is removed at 7 a.m. The “night,” although it is summer, thus becomes 14 hours and the “day” 10 hours.
Follow Specific Dates For Shading
The shading material is put on every day, beginning a certain number of weeks before blooms are wanted, the date depending on the type of mums being shaded.
Here are the specific dates to follow:
- For varieties that ordinarily flower in late October, the shading should be started 9 weeks before blooms are wanted.
- For varieties normally flowering between November 1 and 10, 9 ½ weeks before flowers are wanted.
- For November 10-20 varieties, 10 weeks before.
- For late November varieties, 11 weeks before.
Shading is continued until the buds are about ¾” inch in diameter on the large incurved varieties and until color shows in practically all the buds of the spray types.
Some growers have found that shading may be omitted one night per week without appreciable delay in flowering.
But if it is omitted more than one night a week, the effects of the shading program will be largely offset.
Ideal Shading Material
Any black cloth with a sufficiently close mesh to shut out the light, which will withstand the weather, is suitable for shading mum.
Several firms make cloth specially for the purpose since there is quite a great demand for shading mums.
Several firms will usually sew the cloth to specified measurements, which is a distinct advantage if the plots are large.
The best material available locally is black sateen, though to be sufficiently light-proof, it should have a mesh at least as close as 64 by 104.
If you have a photographer friend who uses a photoelectric exposure meter that reads in foot candles, this will quickly tell you if any material is sufficiently light-proof.
The meter reading under the cloth should not be over 2-foot candles in bright sunlight.
The shading material must lie wide enough to lie on the ground 3″ or 4″ inches along the sides when draped over the framework and long enough to fold around the ends and overlap at least 6″ inches.
The thing is to arrange it so that it completely excludes light.
The overlapped ends are fastened by tying or some other means. Even several large safety pins will do the trick.
The framework has to be rigid, and yet it should not be made of such heavy material that it shades the plants appreciably during the hours that shading is not wanted.
It should not be less than 4 feet high, and it would need to be considerably higher for very tall varieties.
As to width, it’s best to allow 8″ inches beyond the outside rows of plants if 2 or 3-stemmed plants are grown or 10″ to 12″ inches if bushy plants are grown.
For practical reasons, it’s advisable to make the framework rectilinear, square or oblong.
Proper Shading Material Framework
For the uprights of the framework, steel fence posts are ideal, but there is any number of suitable substitutes.
The sidebars at the top may be No. 9 fence wire, ½” inches pipe, 1” by 2” inch furring strips, or any other material that would fill the bill.
If the wire is used, turnbuckles will be needed to keep it tight. Also, braces will be needed to keep the framework rigid.
The posts should not be more than 8’ feet apart and should be connected at the top with rigid spreaders, say 1” x 3” inch boards for the end pairs and 1” by 2” inch furring strips for the others.
To keep the cloth off the tops of the plants, No. 18 wire or heavy cotton twine is run across the top between the sidebars at 1-foot intervals.
The Shading Program
Now, as to the actual program of shading.
First, decide just when blooms are wanted. Then figure out when shading should start by working backward from this date—9, 10, or 11 weeks, depending upon the normal blooming time of the varieties you will shade.
For bushy plants, the last pinch should be made when shading is started.
The first pinch should be made 6 weeks before then, and the second pinch 3 weeks before.
Rooted cuttings should be potted or set in their permanent place 3 weeks before the first pinch, and the cuttings should be put in sand 3 weeks before this.
Thus, once you have decided when blooms are wanted, you can figure backward from that date to when each preceding step should be taken.
For large individual blooms, the single pinch is made 37 days before shading is begun.
The rooted cuttings are planted 3 weeks before pinching, and the unrooted cuttings should be placed in sand three weeks before this.
Shading Program Disadvantages
It may be well to point out that shading, like many other good things, does carry some hazards and advantages.
For instance, during July and August, the sun is still pretty hot at 5 p.m., and covering plants at this hour makes for a hot, close, and possibly moist atmosphere.
This is an ideal condition for the growth of bacterial and fungous diseases and some insects.
Strict attention, consequently, must be given to the spraying program.
Some enthusiasts have recommended that the covering should be removed after dark and replaced before daylight the next morning in very muggy weather.
This undoubtedly asks a great deal of anyone, but one never knows what to expect of a real gardener!
Suggested Chrysanthemum Varieties
Probably any chrysanthemum variety will respond to shading, but as a matter of fact, not all varieties are suitable because their color is adversely affected.
The following list is selected from a list recommended for commercial shading.
Needless to say, only varieties from one or the other of the two groups below should be planted under the same shading frame.