Greenhouse Canada

Features Crop Culture Inputs
Growing in the Green: A few pointers on holiday season

June 9, 2008  By Melhem Sawaya

’Tis the season, to begin your preparations for the perfect Christmas – not New Year’s – crop

With this month’s feature, I am going to share with you some important guidelines about producing a Christmas holiday crop. It can be produced year-round. A large grower in France produces poinsettias year-round very successfully … and profitably.


It’s important to graphically track your poinsettia crop.

It’s important to get off on the right foot. A healthy well-rooted cutting is obviously the basis for a good start. Here are some of the characteristics of a healthy cutting for which to aim:

1. Root to the side of the propagating media.

2. The propagation media should be inside a liner, so that the root hairs are not dried up.

3. A healthy rooted cutting should be only three to four weeks old. Older rooted cuttings, five weeks or more, will be harder to get established in the final container.

If you are not propagating your own, do not hold onto the cuttings until you have time to plant them. It is critical to plant 21-day-old to 25-day-old cuttings. If you are buying rooted cuttings, make sure they are not over 28 days in age.

4. A compact cutting is a must for an even bloom canopy with the finished product. Therefore, the height of the cutting above the rooting media should not be more than 3-4”.

5. It’s critical that cuttings have adequate nutrition because each of these leaves are the umbilical cord to the new breaks until the new breaks are well established. If leaves are starved to the point of turning yellow, you’ll find that when the plant is pinched, the nutrient supply to the new breaks is drastically slower and the breaks are weaker, independent of the amount of fertilizer applied.

The media should drain well and be very porous. This is simply because the poinsettia crop is grown during the dullest weather of the year. Since we mainly depend on liquid feed for nutrition, it’s therefore quite important the media should provide good drainage and air porosity.

I would like to caution that media containing a high percentage of perlite and vermiculite do not necessarily have a high rate of drainage or air porosity. Perlite that is in dust form or of very small particles is a setback, in my opinion, rather than an enhancement. Also, vermiculite that is not expanded could be a waste of money.

Premixed media bags that claim they have more fluffed media per equivalent cubic foot bales should be checked carefully because any over-compressing of these ingredients will affect the physical structure of the media.

The difference between ending up with a good crop or a medium crop depends also on some planting procedures and treatments.

  • Fertilize rooted cuttings before planting, not right after planting. Roots reach for lower salt media.
  • Pots filled with potting media should be moistened with a fine nozzle or long interval of mist. Watering hard upon planting will damage the desirable soil texture by 20 to 30 per cent.
  • If it is possible, water the planted cuttings with mist until new breaks are established. This will speed up rooting and will enhance breaking action. But a note of caution! Use the mist as a watering application; that is, run the mist for 10 to 15 minutes when the plants need watering, not just mist every half hour or so.
  • There are a number of media choices, including Oasis, Jiffy and Ellegard liners. The latter are proving to be a great rooting media and also the best with transplanting success, in my opinion. If I am rooting cuttings, the Ellegard liner is my top choice for two reasons.
  • The rooting process is more successful in producing a healthier rooted cutting, due to the fact that we do not need to mist as much compared to an Oasis media.
  • Transplanting a poinsettia rooted cutting in Ellegard into the final growing pot is much more successful compared to other media, in my experience.
  • Plant the rooted cutting so that it is slightly under the pot media level. Some old habits of putting a Jiffy on top of the media so that it will root better have been proved to be invalid and unnecessary. As well, the pot will look ugly with lumps on top of it.

A continuous feed is a must for any plant, but especially poinsettia. Plants are exactly like human beings in that they need regular, nutritionally well-balanced meals, instead of gorging one day and then dieting for a week.

Watering during the early stages is critical because the roots need to be established properly in the shortest period of time. Watering lightly and not oversaturating the media is a must. Over-watering will promote roots that are inactive. These are the roots that don’t have any hair roots, which are the main means for water and fertilizer intake.

We’ve talked in other articles about fertilization types and concentrations. Here are some guidelines:

  • Do not feed ammonium-based fertilizer when temperatures are below 65ºF due to ammonium toxicity. I would use up to 40 per cent of the nitrogen source as ammonium fertilizer until Oct. 1 to 10, but no later. At that time, you should shift to nitrate fertilizers.
  • As we said before, fertilize at every feeding and at higher levels when there is a long duration between the frequencies of watering.
  • Testing the soil in-house every time, or every week, just before watering and fertilizing accordingly is a must, not a choice. An EC meter should be part of every budget and any bank prerequisite for approving any loan.
  • A media should have the proper pH, and nitric acid is the acid to use, though caution must be taken in using it because it is very harmful if it spills on the person handling it. Therefore proper equipment and procedures must be strictly followed. Poinsettia prefers a pH of 5.8, except some studies show that the darker leaf varieties do better at 6.2. A pH of 6.0 is optimal.

Growth regulation does not only mean chemical application of Cycocel, B-Nine, A-Rest, Bonzi or Sumagic. Growth regulation is the result of an integration of several different factors that lead to the desired height and condition of a plant. Here are some of the factors:

  • Amount of water and frequency of watering.
  • Type of fertilizer and rates used.
  • Variety.
  • Photoperiod.
  • Temperature and temperature deliverance.
  • Light levels.
  • Spacing.
  • Chemicals.

Due to lack of space, we are going to suggest some guidelines for using chemical growth regulators only. The main principle in using a chemical growth regulator is to regulate the growth of the plant rather than stopping its growth for 10 days and then letting it resume again. Therefore, frequent lower rates of a chemical application are a better choice for a quality product.

The use of Bonzi and Sumagic are widely used in the southern U.S due to the high temperatures. A-Rest is rarely used because it is economically prohibitive. Cycocel and B-Nine are used separately or as a combination. However, a note of caution: B-Nine shouldn’t be used on the finished crop in any form three weeks before flower initiation.

Spray stock on a weekly basis with 1,000 ppm Cycocel and 1,000 ppm B-Nine combination past the critical pinch.

Spray cuttings at the same rate and combination on Day 11 and Day 21 from rooting.
Spray the same rate and combination when breaks are 3/4” to 1”.

Graphically track the crop. Three weeks before flower initiation, use Cycocel only. Do not exceed 1,500 ppm per spray. Spraying will even the breaks while drenches don’t.

Use a drench as a final application. Use only 1,500 ppm, rather than 3,000 ppm, which damages the roots most of the time due to the high salt levels at the concentration. Also, our tests show that a 1,500-ppm drench or a 3,000-ppm drench gives just about the same height controls.

Do not apply any growth regulator beyond three weeks from short days, e.g., ‘Annette Hegg’ not past Oct. 11. This will lead to very small bract size. This is not to be confused with small bract size due to low growing temperatures at the time of bract development.

Due to the different regulations from province to province, state to state, or country to country, it is better to leave specific recommendations to local extension specialists. But here are some of the problems to watch for and try to prevent.

  • Fungus gnats are detrimental in propagation, especially if you direct-stick your cuttings. Therefore, a preventive insecticide is to be applied on Day 11 from sticking. It’s the larva, not the adults, of the fungus gnats that cause the damage by eating the roots.
  • Whitefly is still the Number One enemy for the crop in its finishing stage. Control should start at the stock plant stage and not nearer the shipping stage. Most infestations are noticed at the first sign of frost when whiteflies scurry inside greenhouses from the fields.
  • Spider mites could cause big problems during the hot days of stock production or in high hanging baskets where we can’t reach to check, and where normally it is drier.
  • Thrips are not fussy eaters. They don’t spare poinsettias, where you will find significant damage.
  • Rhizoctonia causes brown stems at soil line levels.
  • Pythium is a root disease that starts at the root tip.
  • Phytophthora is a colourful disease. The infection spot starts with a pit, which turns brown. After that, the stem develops black streaks and the leaf turns grey. Then the entire leaf turns brown to black. The roots and bract rot and the disease progresses, until the whole plant dies.
  • Thielaviopsis (Black Root Rot) includes roots that develop black, rotted areas, and stems that develop black spots; finally, spots may develop on the underside of the lower foliage. The infected plant shows lack of vigour with yellow leaves, then a complete collapse of the plant. The disease is favoured by low temperatures and wet conditions.
  • Botrytis is the most notorious disease in poinsettia. It develops under high humid conditions. A grey, fuzzy mycelia is formed on rotted tissues.

Timing or production planning is the most important factor of growing any crop. If everything is done at the proper time even if it is not 100 per cent, you can still end up with a fairly good crop. However, if everything is done 100 per cent correctly, but not at the right time, then you will have a gorgeous crop that nobody wants. Ever try to sell Christmas poinsettias on New Year’s Day? Timing is everything.

Melhem Sawaya of Focus Greenhouse Management is a consultant and research coordinator to the horticultural industry. Comments on this or any other article are always welcome by e-mailing him at .

Print this page


Stories continue below