Growing in the Green: The latest on liners

September 25, 2012
Written by Melhem Sawaya
A programmed vegetative liner is a liner that is grown in such a way as to achieve a predetermined target. The target could be variable, depending on different factors such as:
  • The pot size in which the product is to finish is important information. Programming a liner for 4” pots is completely different from finishing a liner for 12” patio pots or large hanging baskets. For a 4” pot, we need a bushy, well-branched liner full of buds that will take the least time possible to fill the pot just as the flowering buds start to show colour.
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A Rieger begonia, off to a good start.
PHOTO COURTESY MELHEM SAWAY
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The liner that is planned for large pots needs to be in the vegetative stage and not full of flowers. A few examples are bacopa, New Guinea impatiens and fuchsia.

Treatment of liners ending up in combinations could vary from liners intended for 4” or 12” due to the fact the combination products have to complement each other, rather than compete.

YOU HAVE TO KNOW THE SALES DATE
  • Knowing the sales date, as simple as that seems, is one of the most important factors in producing a programmable liner.
  • Programmable liner production is adjusted to fit the season. Liners produced for early spring production are completely different from liners produced for summer production.
  • Many liners are produced for a particular geographic location. Liners for northern states are different from those produced for southern states.
  • Knowing the greenhouse environment of the finishing container will also cause the programming of the liner to vary.
  • The culture practices of how growers finish their crops vary, and if we are to program a liner properly, we must know those practices. Examples include wet versus dry growers, the type of fertilizer used and the use of growth regulators.

WILL THEY BE MACHINE OR MANUALLY TRANSPLANTED
  • If plugs are to be machine-transplanted versus manual transplanting, the media in which the cutting is rooted makes a difference, as does the configuration. This is an important aspect when efficiency is a consideration.
Knowing the previous factors will allow the producer to program the liner towards a specific target.
There are a number of factors involved in producing a programmed liner.

Stock: Starting a vegetative programmed liner with a healthy cutting without flowering buds will help in successful rooting. A budded dahlia cutting, of the same cultivar, versus a non-budded cutting, will take up to two weeks longer to root – if it is able to do so before fungus gnat larvae take over. Fuchsia, nemesia, osteospermum and scaveola are a few examples for this rule. 

Here are some steps stock producers take to avoid shipping budded cuttings:
  • Know the photoperiod response for bud-setting and do the opposite to keep the stock vegetative. Give long days to dahlia and avoid long days for fuchsia.
  • Even if we take care of the photoperiod to prevent bud-setting, if the stock is not harvested in a timely fashion, the cutting will often have buds due to age. Many poinsettia varieties set bud past the 13 to 15 leaves of growth stage, as do chrysanthemum, dahlia and osteospermum.
MONITOR TEMPERATURES TO MINIMIZE BUDDED CUTTINGS
  • Proper temperatures must be provided for minimizing budded cuttings. Many varieties will set bud even when photoperiod and timely harvesting have taken place. Osteospermum, chrysanthemum, poinsettia, dahlia and nemesia, if grown cool, will set the bud. This is a negative characteristic for producing a successful programmed liner.
  • In areas in which it is registered, many stock producers use Florel to keep cuttings vegetatively growing. It is a very effective procedure but is not without some negative side-effects if not used properly. For example:
  1. Many varieties need a waiting period after treatment with Florel or rooting will be delayed drastically; e.g., ivy geranium needs a three-week waiting period.
  2. The time between applying Florel and shipping should be taken into consideration. The normal risk of ethylene damage in shipping is bad enough without increasing it with Florel.
  3. Florel will stress a plant and the level of stress differs for different plant cultivars. A waiting period before harvesting, shipping, or sticking cuttings, should be determined per cultivar.

DON’T ALLOW CUTTINGS TO BECOME DEHYDRATED
■ Cuttings: After cuttings are harvested, all measures should be taken to ensure they do not become dehydrated. Shading the cart, or whatever they are put on, until they go into a temperature and humidity-controlled room will help, but the time between taking the cutting and entering a proper storage room is more important.

Whether cuttings are harvested at the sticking site or have been shipped, dipping them in clean, disinfected water and storing them in a controlled (temperature and humidity) environment for at least four hours (or overnight) will get the cutting turgid and minimize the amount of mist to be applied at the rooting bench in the first two to three days. This is a major procedure to prevent erwinia infections, especially in hot climates or during summer production in northern climates. Poinsettia is a typical example.

THE IMPORTANCE OF WELL-DRAINING MEDIA
■ Rooting media: A media that drains well, is porous and allows the movement of gases and liquids easily is beneficial for fast-rooting and improves the potential of success in rooting.

A peat lite-based media is preferable without gel or other additives to hold the soil together. A rooting media in a cell pack, or other rooting tray, is a good method when the rooting material produces sufficient root mass to enable the pulling of the entire root ball for easy transplanting. 

The media should have good water retention so that over-misting is not necessary. It will result in a healthier cutting with leaves that have not been leached of nutrients. This is more important in hot climates/seasons.

Propagation: For a liner to meet the predetermined target of the quality sales date economically, some aspects have to be taken into consideration.

Liners should be rooted in the shortest time possible to avoid nutrient depletion from the leaves.

Producing a liner with active roots rather than water roots or roots where all the root hairs have dried up.

Avoid using fungicides if possible, because every fungicide has a negative side-effect on new roots – especially if the cuttings are not rooting in a timely fashion. Healthy cuttings, completely turgid, with no shipment shock or dehydration and housed in a proper facility – and under correct procedures – should never need a fungicide.

Cuttings need fertilizer at the first sign of rooting. Well-fertilized liners will branch better and take off better upon transplanting.

Treatments: Selecting the right variety for the finished product is the easiest first step in achieving our goal of producing a programmed liner. Following the required treatments to attain the required end product will differentiate one grower from another and will definitely reflect on the end product. Here are some of the production treatments.

ENSURE PHOTOPERIOD WILL BE ON TARGET
■ Photoperiod: Knowing the variety’s photoperiod requirement and applying it will ensure the right product for the right target.

By not lighting a tuberous begonia, the plants will form a tuber and the plant’s vigour will diminish drastically. At the same time, some petunia varieties, if they don’t get long days (by night interruption) will take much longer to flower or won’t flower.

Long days can be beneficial in speeding up flowering of many calibrachoa when using liners for 4” containers. However, if the liner is for 12” containers, then we don’t want to provide long days because we want the plant to achieve a certain size without any flowers.

A fuchsia intended for a 10” pot should not have any long-day treatment or the cuttings will be budded and growth will slow down prematurely, resulting in an inferior crop. Fuchsia liners intended for 4” production would require long-day treatment on a well-branched cutting.

HIGH-INTENSITY LIGHTING CAN SPEED UP FLOWERING
■ Light accumulation: Many crops will flower much earlier when high-intensity light is supplied because these plants flower by light accumulation. Many cultivars fit into this category.

Petunias and geraniums, to mention a few, can speed up flowering by up to three weeks in northern climates and, although this is desirable on liners intended for mass production of 4” pots, it is not desirable for liners intended for larger containers.

Temperature: Like photoperiod, every cultivar has a growing temperature that will enhance, or is mandatory, for bud setting. Depending on our target, the temperature the liner is grown at should be adjusted to get the optimum liner.
For an osteospermum liner, for 4” production, a low temperature of 50 F (10 C) is preferable and more economical to finish. However, if the same cultivar is intended for a 6” pot or larger, cool treatment should not be applied until after the liner is planted in the pot. Once it has established and pinched, and the new growth is 2”, then a cool treatment is beneficial.

If treatment is intended for 4” production and is planted in a 6” or larger pot, the end product will be too short and not desirable.

Pinching (shearing): If some cultivars don’t branch naturally and chemical branching is too slow or ineffective or has some negative side-effects, then pinching (or shearing) the cuttings is the only way to produce a bushy liner.
Although numerous growth regulators can control the height of many cultivars, pinching can result in much nicer liners – especially when uniformity is required – and, with the advancement of mechanical shearers, this phase of production is less labour-intensive than in the past.

Growth regulators: Chemical growth regulators can adjust the growth habit of many cultivars. The adjustment could be positive or negative, depending on our knowledge and experience with the growth regulator, which is a legendary discussion on its own.

Here are some suggestions when using growth regulators to produce a programmable liner:

Some growth regulators speed up flowering while others delay it. Cycocel accelerates flowering on geraniums while B-Nine delays the flowering of any crop. A-Rest speeds up flowering on almost every variety, while Bonzi and Sumagic could delay the opening of the flower, especially if the plug is grown in cool temperatures immediately after treatment or in less than two weeks.

Growth regulator rates vary drastically under different temperatures. Keeping in mind the liner’s finishing temperature is very important. Bonzi and Sumagic are more critical than B-Nine and Cycocel when it comes to treatments and temperatures because they are effective for longer periods.

Showering or heavily spraying the plants with Bonzi or Sumagic on a budded liner will delay the flowering much more than if these liners were sub-irrigated with the same rate of Sumagic or Bonzi.

Since many liners going into combinations are vigorous varieties, the practice of sub-irrigation (dipping) is common. The whole liner tray is passed through a solution of Bonzi or Sumagic that programs the liner to have more torque and thus slows its growth. This is especially important when these plants are combined with less vigorous plants that cannot handle Bonzi or Sumagic.

The rates for sub-irrigation dip vary but, for a starting guideline, use 2 ppm Bonzi or 1 ppm Sumagic. These rates work well if crops are to be grown at an average temperature of 60 F to 65 F and are an excellent tool when you get to know the varieties and their response to the dip-treatment.

Another growth regulator that can play a huge part in producing a programmed liner is Florel (Ethrel). A liner can be set at zero (date) when sprayed with Florel and, as long as we know how long it takes from last spray to flowering, programming the liner with the proper date and treatment will ensure the product will be ready on time. Different growers get different responses with the use of Florel.

Here are some suggestions for successful results when using Florel:
  • Make sure the chemical is still active. Florel can deteriorate with time, especially if the container is left open. Florel activity can be checked by a simple test.  Adjust your spray water to a pH of 6.0, then add 250 ppm Florel and the water’s pH should drop to 3.2 - 3.5. If it doesn’t, then the chemical is deactivated.
  • The longer the plants stay wet, the more effective the spray is. Florel is very local in its activity, so plants should be covered well. Overspraying is much better than under-spraying. There are no negative side-effects from overspray, but there is definitely no activity with under-spray. 
  • Florel is more effective at 65 F than at 50 F.  Only spray plant material that is not crowded, because the spray cannot get into all parts of the plant, and if the sprayed parts of the plant are not exposed to light, many of the leaves will yellow and may fall off. 
  • It is very important to spray rooted liners as soon as they are turgid enough but still have some space among the cuttings.

LARGER LINERS TAKE LESS TIME TO FINISH
■ Liner size: Naturally, the larger the liner size, the better the chance of producing a higher quality liner. There is more light, more branching and chemical treatments are more effective. In addition, a larger liner will take less time to finish when planted.

If liner size is limited because the liner has to go into 4” pots, and the smaller liner is more practical to plant, then spacing the smaller liners will give the same result as larger liners.

Disease- and insect-free: If the liner is clean of disease and insects and goes into clean media and facilities, the chances of disease or insect problems is much lower. Any chemical treatment on the liners is much cheaper than doing the same treatment after the liners have been transplanted.

Timing: By far the most important factor in a programmed liner is the proper timing, whether it is to do with cuttings, when to apply treatments, or when to adjust the environment as needed during the various stages.

Producing a programmed liner is like flying an airplane – 90 per cent of the time we are off course, requiring frequent adjustments to steer us towards our destination. We must continuously adjust our culture and practices to meet our liner targets and we can only do that if we know where the product is going to end up and the conditions under which it is to be finished.


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; please e-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

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