Please note that this page is under maintance. The majority below has been the standard suggestions for the past 20 years. New info which will be more concise, specific, and covering newer topics is coming soon.
- A CASE FOR 6-INCH DORMANT HYDRANGEAS
- PRODUCING BLUE PLANTS
- D&W HAS NO LIABILITY FOR FLOWER COLOR
- PREVENTING EXCESSIVELY SHORT PLANTS
- REFERENCE MATERIALS
- BASIC STEPS TO PRODUCING A CROP
A CASE FOR 6 INCH DORMANT HYDRANGEAS
MANY GROWERS WITH EXPERIENCE ARE ABLE TO PRODUCE HIGH QUALITY HYDRANGEAS FROM 4-INCH DORMANT MATERIAL. ON OCCASION, however, due to various reasons, production problems are encountered, even by experienced growers. A review of the methods resulting in good rooting of 4-inch material into soil in 6-inch or larger pots is in order to understand where 6-inch material fits in a production plan.
Reasons for poor rooting of 4-inch dormant hydrangeas are:
1. Drying of the 4-inch root ball and subsequent shrinking of the 4-inch ball from the soil used to fill the final pot. Remember, the plant starts to leaf out while most or all roots are in the 4-inch ball. Water depletion in the 4-inch ball occurs very fast and may not be noticed, especially if fresh soil covers the 4-inch ball. Two practices can help to overcome this problem.
A. "rough up" the 4-inch root ball. We used to believe that a simple scoring would suffice but we now believe that a more severe scarification of the 4-inch ball is best to insure close contact with the new soil and to encourage new root growth. We have seen new roots to the side of the pot in two-three weeks using this method with adequate watering.
B. Be absolutely sure to water the 4-inch root ball rather than the new soil in the larger pot. If lead weight watering is used, place the lead weight directly on the 4-inch ball. If over-head watering is used, water frequently enough to keep the 4-inch ball wet. This problem is overcome if ebb and flow irrigation is used.
2. High fertility in the fresh potting soil. Perhaps it is not alone the high fertility in the 6-inch potting soil that is used. It may be that the fertility in the dormant 4-inch ball is quite low and roots acclimated to this low fertility may not readily penetrate the soil with the higher fertility. Fertility is usually low in the 4-inch ball because of efforts to gradually harden the plant prior to storage, to slow growth, and to encourage leaf drop. To help this problem, do not add any fertilizer to the soil used to pot the 4-in plant except for lime, gypsum,and superphosfate as needed for color control. Liquid fertilizer orm dry fertilizer can then raise fertility in both soil masses near equally.
3. High temperature. In some situations, in the south particularly, temperatures are high enough to both inhibit root growth and-most likely- promote top growth to the detriment of root growth.
Producing Blue Plants.
Use of proper variety is of first importance. Keeping a low pH and applications of aluminum sulphate during both the summer growing season and the greenhouse forcing period is second. The third factor of importance is fertilization. Withholding phosphorus, increasing potassium and reducing nitrogen promotes clear blue colors. The summer grower can not guarantee the color in the greenhouse.
Consult the variety discussion for best varieties. At D&W, Kuhnert, Mathilda Gutches, and Merritt Supreme can always be purchased for blue. We will have made 4-6 applications of aluminum sulphate during the summer growing season. In spite of this, continued applications need be made during forcing. Soil must be moist (water the evening before) to prevent leaf burn. Recommendations are seen ranging from 2 1/2 to 14 lbs. per 100 gallons. We suggest 8-10 lbs. per 100 gallons. Again, apply to moist soil. Three to five applications of aluminum sulphate should be made. The first when the plant is established, and about every 7-10 days thereafter.
Fertilization with reduced nitrogen, increased potassium and reduced phosphorous contributes to sharper, clearer blues Potassium level of 350 pm, phosphorus at 0 ppm, and nitrogen at 150 ppm is suggested on a every watering basis. For a 1:100 injector each gallon of stock solution should contain, for example, 6 oz. ammonium nitrate and 10 1/2 oz. of potassium nitrate. Other elements could be given in a second tank.
D&W HAS NO LIABILITY FOR HYDRANGEA FLOWER C0LOR
THIS SECTION IS ADDED TO CLARIFY THE POSITION OF DAHLSTROM AND WATT WITH RESPECT TO HYDRANGEA COLOR.
TO PRODUCE BLUE PLANTS, WE USE VARIETIES THAT ARE EASIEST TO BLUE SUCH AS MATHILDA GUTCHES, KUHNERT, BLUE DANUBE, MERRITT SUPREME, AND BLAUMEISE AMONG OTHERS. THESE VARIETIES ARE TREATED WITH ALUMINUM SULFATE IN THE FIELD DURING THE SUMMER AT LEAST 5 TIMES.
RIGORUS ALUMINUM SULFATE APPLICATIONS MUST BE CONTINUED DURING THE FORCING PERIOD. SINCE HYDRANGEA COLOR DEPENDS ON SEVERAL FACTORS BEYOND OUR CONTROL, WE CAN NOT GUARANTEE COLOR.
AMONG THE FACTORS WHICH INFLUENCE COLOR DURING THE FORCING PERIOD ARE:
SOIL pH ( ACTUALLY SOLUBLE ALUMINUM)
SOIL BUFFERING CAPACITY
AVAILABILITY OF NUTRIENTS (IE HIGH POTASSIUM, LOW PHOSPHORUS, AND LOW FERTILITY FOR BLUE HYDRANGEAS)
APPLICATIONS OF ALUMINUM SULFATE DURING THE FORCING PERIOD
OTHER FACTORS NO DOUBT INFLUENCE COLOR:
WE THINK ONE OF THE BEST DISCUSSIONS OF HYDRANGEA COLOR WAS WRITTEN BY THE LATE DR JIM SHANKS AND PUBLISHED IN THE BALL RED BOOK 14TH EDITION. THE MOST RECENT "REPRINT" OF THIS INFO IS TO BE FOUND IN THE BALL REDBOOK, 16TH EDITION WHICH BOB MILLER MODIFIED AND UPDATED FROM SHANK'S ORIGINAL ARTICLE.
PLEASE ACQUAINT ALL PERSONNEL WITH THIS INFORMATION.
AGAIN WE REPEAT THAT WE ARE NOT RESPONSIBLE FOR FINISHED HYDRANGEA COLOR.
PREVENTING EXCESSIVELY SHORT PLANTS
We have discussed reasons for poor rooting out of the original root ball. These factors are the primary reason why plants--4-inch plants especially--may fail to grow to the height expected.
If plants are still too short in the view of the grower, growth regulators can be used to cause elongation if the problem is diagnosed early enough.
These suggestions should be adhered-to carefully.
Gibberellin material applied as a spray once or twice beginning when the flower heads are no bigger than a pea or at most a dime will increase plant height without influencing flower head formation. If applied later, flower heads can be very adversely affected--that is they will be loose, open and often unsaleable.
We use Pro-Gib, a named brand product, containing gibberellin in the amount of .0391 percent active ingredient. Applied at 5 ppm active ingredient (that is, 5 mls per 10 gallons of water) as a spray to run-off, this product has helped considerably. A second application can sometimes help in forcing very early crops (pre valentines day finish).
It is important that the grower responsible be aware of potentially short plants so as to apply growth regulator early so as not to harm the flower head. Plants should be watched carefully during the first 3 weeks and if there is an indication of failure to elongate, an application can be made.
The effects of Pro-Gib on elongation can be overcome with B-Nine applications but ill effects on flower development can not be helped.
We emphasize that the finish grower is responsible for Pro-Gib usage. In our situation at 42 degrees north latitude, with heavy winter rainfall, and fog, we use Pro-Gib as a treatment on all plants forced for Valentines Day and earlier.
Intermittent night lighting has also been used by growers at northern latitudes (Canada, Europe). They have shown that this night interrupt lighting has helped and significantly increased internodal elongation on hydrangeas.
Remember also that hydrangea forcing for the Valentines Day holiday is difficult . Not only are days short, weather often dark, but time constraints mean that hydrangeas shipped for this period have received just about 6 weeks of cooling while plants shipped for Easter and later have received 4 to 8 weeks more. More cooling equals more elongation all other factors being equal.
Basic Steps To Producing a Crop
*Upon receiving plants they should be unboxed promptly (same day if possible), moved into a greenhouse, and watered. Plants should be allowed to acclimatize for several days in the liners they are shipped in or in some sort of tray before they are potted into their finishing containers. Upon potting it is very important to cover the existing root ball completely with new media. This helps to prevent the root ball from drying out before the new surrounding media dries. Uneven drying can cause the root ball to shrink away from the new pot media. This can result in the root ball becoming to dry and the plant dying or becoming stunted. (See "A Case for 6-inch Hydrangeas", above)
*For early crops including those forced for Christmas, January and February finished sales you should refer to the above info on preventing excessively short plants. Short plants are always an issue with winters short days, low light levels and cooler temperatures.
*Hydrangeas grow best when they are started and finished cool. Starting a hydrangea around 60*F is good in a greenhouse situation. Cooler temperatures will promote better root growth which is key to getting your hydrangea off to a good start. After the first month you may be inclined to raise the temperature to get the plant moving along and make your sale deadline! Remember that temperatures over 70*F will increase the rate of leaf and bud development but can decrease overall quality of the plant. the best temperature we have found for forcing a hydrangea in a greenhouse is 65*F (a good balance between cool and making the sale window). The cooler the finishing temperatures the more hardy the plant and often brighter more distinct the color. Shading the greenhouse upon first color in the flowers is basically a requirement as finished flowers will often burn under high light (if you have not already had the plants under some shade prior).
*Under such cool conditions mildew and other fungal pathogens can be your worst enemy. It is strongly recommended that within the first two weeks a fungicide application be made as a preventative and the crop monitored closely thereafter for follow up applications. One of the many things to consider is residue. Many fungicides leave residue which can be very unattractive on foliage. Most books including the Ball Red Book give recommendations on what to use although newer fungicides are flooding the market which have proven to be very beneficial. For recommendations on fungicides please email Dahlstrom and Watt or click on the front page link for Kurt Miller.
*Growth regulator applications are often needed. B Nine is a preferred PGR for most growers. Applications are most generally made in the middle of the growth cycle from about 4 weeks in the greenhouse until just before plants begin to show color. If B-NINE is applied just as flowers are beggining to show color this can reduce slightly your overall flower size. This is not generally desired however on some soft flower headed varieties or if you are having excessive hot conditions this can help firm or stiffen the flower head. We have seen the number of applications range from 0-5 depending upon what height you are looking to attain. Often early crops require little to no growth retardant PGR's. Easter and later crops often require one or more applications. Rates of B Nine can range between, but are not limited to 500ppm to 5000ppm. Remember with all other conditions equal higher light levels will keep plants shorter as compared to lower light levels making plants stretch.
*Blue applications should not be initiated until at least the 4th to 5th and even 6th week as to help the roots to move out into their new surroundings. Lessening the chance of burning young new roots that will keep you plant A#1 quality. (refer above to "Producing Blue Plants")
*Insect pests can be a problem, mainly aphids and mites. Please check you pesticide labels for hydrangea and test before spraying your whole crop.
*Hydrangeas are a very sensitive plant. Use caution with pesticides as some fungicides and insecticides can act as weed killers and PGR's on hydrangeas! Even pesticides labeled or even used by you in the past can have varying effect under climactic and other such differences.
*The info provided in these basic steps is by no means all you have to do to produce your hydrangea, rather a quick reference to some of the more critical steps. Other methods are available for some of these suggestions. More complete info can be found in some of the references below and other quality publications.
We believe one of the very best discussions of hydrangea culture is to be found in the Ball Red Book, 14th Edition, written by Dr. James Shanks of the University of Maryland.
Dr. Shanks died several years ago and since that time Bob Miller of our company has revised his article sticking closely, with permission from the Shanks family, to Jim=s original suggestions where possible.
This discussion is to be found in the 16th edition of The Ball RedBook, Ball Publishing, Batavia, IL 60510.
Additionaly Dr. Doug Bailey has published Hydrangea Production, Timber Press, Portland Oregon. This book covers many aspects of hydrangea production and many find it useful.