When starting plants from seed, we prepare flats with soil amended with peat, perilite and a little bit of pine bark. We then scatter seed over the soil (not in it) and top dress with a thin layer of fine sand. We label each flat with the plant name and date we sowed. The flats then go on propagation benches lined with heat mats. If you'd like to try this at home and don't have heat mats, try substituting electric heat tape used to keep pipes from freezing. Once the seeds have germinated and put out their first set of true leaves, the flats come off the heat mats. Throughout, we water our seedlings with permanent misters mounted over the benches. At home, you can use a mist bottle four or five times daily. Make sure your new plants are getting plenty of sunlight and if it's only from one direction, turn your flat at least once a day.
Once seedlings have two to three sets of leaves, we transplant them into a larger container--either cell-packs or small pots. Putting a new seedling into too large a pot will allow excess water to collect and could rot the plant. Pansies, petunias or other cool weather plants can go onto a porch or covered area in mid to late March. Summer annuals shouldn't go out until danger of frost has passed (when planting at home, count backwards using the germination time on your seed packets).
For cuttings, we start with a two- to four-inch stem from the plant we want to propagate. We strip the bottom leaves, being careful not to damage the plant, and then dip the stem into a root hormone to give it a jump-start. We place the cuttings in a flat using either a sand/bark mixture (good if you over water) or the same peat/perilite mix we use for seedlings. When placing a cutting in soil, we make sure at least one node (where a leaf was removed) is in the soil, as it will root more easily. We gently press the soil around the stem so the cuttings are stable. If we're rooting something with large leaves, we cut half of each leaf off so the stem can put more energy into rooting and less into maintaining leaves. Again, we use a heat mat and mist, mist, mist since plants that already have leaves are more prone to water loss, especially in bright sun. After two to three weeks, we gently tug on the plant to see if it feels firmly rooted. When the roots are secure, we transplant into a 3"-4" pot or container. Once we've stepped up to a larger pot, it's time to pinch the new plant back at least twice so it will be full and bushy when it goes into the ground.
For both cuttings and seedlings grown at home, it' best to harden the plants off outdoors before placing them in the ground. You can acclimate plants by moving them onto a porch or a covered area for a week, then move them into dappled sunlight, then partial sunlight until they are at last ready for full sunlight. Happy gardening!
About the Author
Bruce Ballard, Biltmore Estate Landscape Supervisor, has worked in the gardens of Biltmore Estate, George Washington Vanderbilt's turn-of-the-century home, for more than fifteen years. Encompassing both formal and informal designs, the 75 acres of gardens and grounds are at the heart of the nearly 8,000-acre estate. Ballard oversees the day-to-day operations of three garden crews, responsible for approximately 100 acres of garden and roadway.