To understand how to grow a quality plug, you must first define what a quality plug is. Some will argue a quality plug is simply one that is able to be transplanted and, with some work, will grow into a quality finished product. To me, this couldn’t be further from the goal. A quality plug in my opinion is one that is able to be transplanted and finished with minimal additional inputs. The more you need to “fix” a liner in the finished stage, the more you lose off your bottom line.
In order to achieve this goal, the plug must be produced so it is well toned, well branched and ready to take off running as soon as it is transplanted. This could include having bud initiation, depending on the crop. Poor quality inputs will generally result in poor quality results.
Our production methods have been developed to work toward the ultimate goal of our definition of a quality plug. The main principle is to develop a healthy, well-branched plug that is neither weak nor branched well above the soil surface. To achieve this, we first maximize the use of pre-germination growth regulators. By spraying the soil surface of the plugs with regulator prior to germination, it greatly reduces the elongation of the plugs.
As the roots emerge, they grab a small amount of regulator and take it up into the plant. This gives a very minute dose to the plant, but it is all the plant needs in its young state. As plants continue to grow, roots continue to grab small doses of the regulator, allowing for small amounts of adjustment to the size and tone of the plug.
This method is especially effective when growing crops that exhibit a lot of early stretch like marigolds, zinnias and celosias. This method can be utilized on other crops as well, because the initial stretch is not the only benefit from this method. Much smaller doses can be applied with this method, as well as fewer follow-up applications. It is possible to cut the expenses of chemicals and labor to achieve better results, with less issue of managing re-entry intervals. Our production maximizes the use of these pre-germination regulators on 80 percent of our crops.
Nearing The Finish
Once we have worked through the early stages of plug production with our pre-germination regulators, we try not to utilize additional regulators on our spring crops. Because we have the highest light levels in the country during spring, we can turn our regulation over to light intensity.
Once in Stage 3 of plug production, plugs are moved into the highest light levels so they can grow in as a finished crop. This means all plugs that are destined to grow as a finished crop without shade finish as a plug without shade–this applies 24 hours a day. Those crops that are grown as a shade-finished plant finish as a plug in 30 percent shade. This allows for the light level to heavily tone the plug without stalling it out. As mentioned earlier, the goal is for this plug to hit the ground running as soon as it is transplanted. In general we do not add any additional regulators on spring crops beginning in Stage 3.
The additional light level also increases the natural branching of plugs, as well as speeds up the blooming on light accumulation crops. Combining the high light level with nighttime interruption lighting has shown up to a two-week-faster bloom of a petunia plug, as one example, compared to one grown in much lower light levels–also grown with nighttime interruption.
Growth is also increased by not having delay from late application growth regulators in the plug. You should never have to push your plugs out of the regulator after transplant.
While there are, of course, many other factors that determine a quality plug, the ones I have mentioned can often get overlooked. Unfortunately, overlooking these principles can add a lot of stress and additional work for the grower to finish a quality flowering product.
No money is saved by cutting expenses on your starter material. Money spent in young plant production will go 10 times further in producing quality finished product than money spent fixing the initial issues. Maximize your light levels and early regulators. If that is not possible, you will probably be better off purchasing your starter material from someone who can.