Potting Plugs:
Dr. Don C. Wilkerson
Professor of Horticulture & Extension Specialist
Texas A&M University System
College Station, TX

Sometimes the simplest of things can be extremely complex. Take potting and transplanting plugs. This is one of the most basic functions in crop production but if plants are not handled properly at this stage, big problems can arise. Mistakes during potting and transplanting are magnified because of the repetitive nature of the entire process.

Staging and Preparation:
I've always been fond of the old saying, "prior preparation prevents poor performance." In other words, don't wait until plugs have arrived to order media, pots, flats and inserts. Avoid holding plugs for extended periods prior to potting. Be sure to take all plug flats and sheets out of the case and check their moisture status. Stressed plants don't take off as quickly and can even become stunted and delayed.

Growing Media:
Most growing media should be moist but not saturated for potting and transplanting. If the media is too wet it can be over compacted, pressing out valuable air space. Pots, flats and inserts should be filled with media to the appropriate level and carefully compacted to achieve a balance between air and water holding capacities. This will also determine the ultimate depth of the plug in the container. If media is not adequately compacted, plugs will settle too deep following irrigation. This situation can predispose plants to several fungal diseases.

Pre-dibbled holes can speed up the transplant operation but compaction is the key. Good contact between the root system and media is very important for getting young plants established.

Handling Seedlings and Plugs:
Young seedlings have tender stems that are easily crushed. Seedlings should always be handled by their leaves to avoid this problem. Also, care must be exercised when lifting bare root seedlings from seed flats or trays. Seedlings should be carefully pulled from the germination media to avoid root injury. Broken and torn roots provide an ideal entry site for phythium, phytopthora, rhizoctonia and other harmful disease organisms.

Removing plugs from a tray also requires care. It always helps if the media is well watered prior to this operation. Push plugs out from the bottom of the tray and avoid pulling them out by their leaves and stems. Although mechanical extractors can speed things up, they are frequently hard on young plants. Watch carefully to make sure seedlings and plugs are being removed properly.

Where a plug is placed in the container is important. Since spacing is already at a premium, plants should be placed in the center of the pot or insert. Offsets are frequently poor performers and also crowd out adjacent plants. Planting depth is critical. The soil line of plugs and media in the new pot or insert should be the same, following irrigation. Plants potted too deep or shallow will present major problems later in the production cycle. Special care should be taken when pressing plugs in to the media. Too much pressure can result in root injury and subsequent disease problems. A shallow reservoir is often provided to hold additional water during irrigation. The depth of the reservoir may vary depending on irrigation systems and practices.

Quality Control:
Transplanters and transplant lines should be observed and monitored frequently. Quality control standards should be established and closely maintained. This is one area where cutting corners may have serious repercussions.

Needless to say, this isn't rocket science. But many of the problems growers experience later in the crop can be traced back to a lack of attentiveness during the potting and transplanting phase. Hopefully this bit of information will motivate you to keep a close eye on potters and transplanters. Remember, this can be a boring and repetitive job. Employees need to be reminded of your quality control objectives along with production goals.

I recall an incident where a grower proudly told me that his crew had broken all previous records for the number of flats potted in a day. I didn't have the heart to tell him that most probably would not survive because they were buried so deep you could barely see the leaves.

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