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Vol. 12(4), pp. 2-9The McAllen International Orchid Society JournalApril 2011

Repotting Seedlings

R J Ferry

When plants have been ordered from a commercial establishment, it is not uncommon to see them arrive in small plastic 2-inch square seedling pots that are all of 3 inches deep. Some may even arrive in 3-by-3-by-3 pots. Whatever the pot size, each of these plants is a seedling requiring a more tender potting protocol than would be necessary for a mature plant.

Fig. 1. A group of paph & cat seedlings on potting table; most in 2-inch pots. Photo taken after unpacking, giving a light misting, and allowing pots to stand upright for 72 hours. Digital photoDSC_3890; Thur-27Jan11.

In contemplation of the annual MIOS repotting and plant sharing meeting in April, a few digital photos were taken as various seedlings were potted. Some were cattleyas and others were paphiopedilums, but the repotting regimen was about the same for all. The plants arrived, and each was wrapped in newsprint and had been carefully padded. The first step was to gently unpack each plant, take an inventory of what had arrived, and give the potted plants a light misting and allow them to stand upright for 72 hours in "reasonable" light (not overly bright, but enough to encourage leaves to resume their natural growing posture. This was the case with the group of plants below, after being unpacked and allowed to stand on the potting table under the light (Fig. 1).

The next step was to move the plants away from the immediate area where each would be repotted, and have the necessary potting material close at hand. The potting materials included a good supply of medium-to-fine firbark, coconut fibers, fresh New Zealand Sphagnum moss, small chunks of limestone, and plenty of water. Most of the seedlings were "overpotted:" into four or six inch plastic pots. This may be a cause for criticism from some circles, but it's been this worker's experience that smaller pots tend to dry out much too fast, and these sizes also allow for plenty of room for root growth.

We begin by putting a layer of medium-sized bark in the bottom of the pot to allow for drainage (Fig. 2). This was overlaid with a thin layer of Sphagnum. In some cases, a thin layer of coconut fiber was substituted for the Sphagnum, but either serves basically to act as padding over the medium bark (Fig. 3).

Fig. 2. Base layer of fir bark in 6-inch plastic pot. Digital photo Wilma Ferry, DSC_3891; Thur-27Jan11.

Fig. 3. Fir bark covered with layer of coconut fiber and sprinkled with limestone chips. Digital photo Wilma Ferry, DSC_3892; Thur-27Jan11.

Over the sprinkling of limestone chips is laid a layer of Sphagnum and a layer of finer bark, both of which are moist. The seedling (in this case, a paph) is gently depotted from its seedling pot, so that any of its original mixture falls into the new pot and is readily available to the plant (Fig. 4).

Fig. 4. Paph seedling depotted from 2-inch pot. Caution: the seedling and its roots are fragile! Digital photo Wilma Ferry, DSC_3893; Thur-27Jan11.

In this photo (Fig. 5) it's obvious the first concern for a newly potted seedling is to grow roots! Part of this culture is to ensure the present roots receive minimal damage during repotting of the seedling!

Fig. 5. Paph seedling depotted from 2-inch pot. Note the seedling's sparse hirsute roots. Digital photo Wilma Ferry, DSC_3894; Thur-27Jan11.

Once fully depotted, the seedling is held in position, it's roots are teased into comfortable positions within the pot, and the moist media is eased around the roots (Fig. 6). This is a mixture of a finer-grade bark mixed with some Sphagnum and the potting mix in which the seedling arrived. Nothing is wasted! During this phase, the plant is held firmly but gently in the proper position.

Fig. 6. Roots spread and plant held vertically, the potting mix is gently firmed around plant. Digital photo Wilma Ferry, DSC_3895; Thur-27Jan11.

As the potting mix is firmed around the plant, care is taken to keep the plant centered and firm the mix around the inside rim of the pot; not putting great pressure on the plant itself (Fig. 7). Speed is not essential; attention to detail is!

Fig. 7. While holding seedling in place, the potting mix is packed around plant. Digital photo Wilma Ferry, DSC_3896; Thur-27Jan11.

The plant is now holding in place, but close inspection shows it's still a bit wobbly and could be stressed by overly strong air movement. A little more potting mix is added and gently firmed into the pot around the plant (Fig. 8).

Fig. 8. With paph seedling holding in place, more potting mix is added. Digital photo Wilma Ferry, DSC_3897; Thur-27Jan11.

With the additional potting mix added, another light sprinkle of crushed limestone chips is added. The well water used to water plants in the greenhouse is slightly alkaline, and these will add to the acidity of the substrate (Fig. 9).

Fig. 9. With paph seedling holding in place, another sprinkle of limestone chips is added. Digital photo Wilma Ferry, DSC_3898; Thur-27Jan11.

We're now into the "finishing touches." A thin layer of Sphagnum moss is laid over the limestone chips (Fig. 10).

Fig. 10. The limestone chips are covered by a thin layer of Sphagnum moss. Digital photo Wilma Ferry, DSC_3899; Thur-27Jan11.

Over this thin layer of Sphagnum, still another layer of potting mix is added, and the plant is checked for cleanliness and general appearance (Fig. 11).

Fig. 11. Over the Sphagnum moss, a final cover layer of the potting mix is added. Digital photo Wilma Ferry, DSC_3900; Thur-27Jan11.

With the addition of the final layer of potting mix, the plant is gently sprinkled to remove any stray potting mix parts from leaves and it is now all-but-ready to be benched in the greenhouse or other appropriate place to receive early morning sunlight, but not the harsh light of mid-day or later (Fig. 12).

Fig. 12. The newly potted plant is now all-but-ready to be benched. Digital photo Wilma Ferry, DSC_3901; Thur-27Jan11.

Don't be so hasty! We're not fininished! It's important to add the plant tags! It's one thing to have a shipment of plants come in and be repotted, but it's also important to include each plant's tag in the pot! You may think you know what you have, but after potting several plants, the seedlings can easily look all the same! As each plantlet is finished being potted, make certain you have the plant's tag close by so it can be gently slid inside the pot. Look again at Fig. 12, and look closely at the plant tag lying on the potting table on the right side of the potting tray in the figure. Don't get in a rush and neglect to properly tag each plant.

Had this been a plant for your editor's collection, the plant tag would also carry a plant number. Its plant number would have been the date (day-month-year) the plant was received, followed by 1, 2, or 3, and so forth for each subsequent plant received on that date. Note that the date is expressed as day-month-year, not the month first, so the first plant received on--say--15 January, 2011 would be Pl#150111-1, the second plant would be Pl#150111-2, and so forth. This matter of plant numbering may seem like a very minor thing, but over the past forty and more years, it has turned out to be not only a very useful system, but one that has helped to re-identify plants that would have otherwise been hopeless cases where plant divisions have been shared and much data lost. Be meticulous, and consistent, pay attention to the small details, and keep records of your plants and how you care for them. Over the long haul, it will make a great difference in how much you can learn and how much learning you will be able to retain! Taking the time to keep good plant records is a great way to combat forgetting. In addition, as time passes, your records of years ago can bring back some pleasant memories of people, plants, places and events. Trust your journal editor on this one: it's worth it!

Fig. 13. Seedling plants potted on 27 January, 2011. Digital photo DSC_3981; Thur-31Mar11.

The previous pages have outlined a little of the potting of a shipment of several orchid seedlings that arrived in early January, 2011. As this is written in late March, the seedlings have not only survived, and all are healthy (Fig. 13).

Fig. 14. Pl#020809-29. Phragmipedium lindleyanum. Digital photo DSC_3983; Thur-31Mar11.

There is yet another aspect to repotting seedling orchids. Don't expect your newly potted plants to burst into flower almost instantly! The Phragmipedium lindleyanum, seen among other young orchid plants (Fig. 14), is one that entered the collection as a seedling on 02 August, 2009. Your editor's plant records indicate: "the space between the plant pot and outer pot is padded with Sphagnum. The potting mix is bark & Sphagnum laced with limestone."

Several months have passed between the hot days of last August, including the winter season with its freezing temperatures of early February, 2011. Now, as April is nearly here, the plant is putting out its first flowers. One important point to remember: when you repot seedlings, have the patience to be an orchid plant grower, not merely one who buys a plant for "instant flowers!"

Copyright © 2011 R J Ferry