Take advantage of any warmer days to care for your bearded iris. Tree leaves are all down and they must be removed to prevent pests and disease. Remove any totally brown iris foliage but do NOT remove green foliage and NEVER cut foliage in a fan shape in the garden. The plants need their leaves to promote growth. The top of the iris rhizome wants to bask in the sun. If weeds are a problem, Preen or another pre-emergence can be applied.
Pre-spring is a good time to apply super phosphate or triple super phosphate. As it contains no nitrogen, it is slow acting, but promotes bigger and better blooms. Avoid getting granules on the rhizomes. TB irises require soil of pH 6.8 to 7.2. Lime reduces the acidity in our clay soil. Get your soil tested to accurately determine the pH. This also a good time to check identity labels as some may have faded or been displaced by animals such as deer. A good practice is to put the iris’ name on the underneath side of the label as well.
Intermediate irises (MDBs, SDBs, IBs and MTBs) are sequentially sending up their bloom stalks. Early and reblooming tall bearded irises are also beginning to show growth. Continue with leaf cleanup. Survey for garden for space to add new irises. Check catalogues and/or on-line growers’ listings.
While you are enjoying your garden of irises, be on the lookout for evidence of borer infestation. The tiny larval stage of a night flying moth starts at the top of the iris fan and chews its way down the plant leaving a slimy hidden trail. Check carefully and eradicate by squashing the invader of use a systemic insecticide-labeled specifically for the iris borer. If not dealt with, the borer continues its feast into the rhizome and can cause rot. If leaf spot is evident spray with a fungicide that is used for leaf spot of roses. Remove spent blossoms and keep beds clean. The last Saturday in April is traditionally the date of the annual iris show. Check your rises regularly for potential specimens in anticipation. Stake a way-ward stalk if required. Enter your iris stalks and enjoy the show.
Later blooming irises will still be lighting up your garden with color. Re-blooming TB irises need a light application of fertilizer and require water if rains aren’t enough. Remove spent bloom stalks by pushing the stalk inward toward the center of the clump and it will snap-off at ground level. Monitor for rot if too rainy. If you grow Siberian irises, they will be in their prime bloom season.
Continue monitoring for borers and clean-up as well. Don’t allow foliage from other fast-growing perennials to encroach on the iris plantings. This is a good time to order new iris rhizomes. A great source for selecting the best and latest “tried and true” introductions is the AIS bulletins. You will find the current winners and invaluable TB Symposium Popularity Poll listings. Check on-line for listing of the Dykes Medal winners. You will also find the advertiser’s section very helpful for ordering. If you are not already a member of the American Iris Society, consider joining. You will receive quarterly bulletins that contain full color photographs with many informative articles. Contact www.irises.org for more information.
Evaluate for replanting and division of rhizomes. Tall bearded iris should be divided every three or four years. If crickets are present and eating holes in rhizomes, cover the rhizome temporarily with creek sand. The Charlotte Iris Society holds its annual rhizome sale in July or August. Dig and prepare rhizomes to contribute to the sale. (This is when the foliage is cut in a fan shape on the dug rhizomes and plants disinfected with a 10% solution of Clorox, the rinsed and dried). Prepare new beds for irises. Remember to check the pH (6.8 to 7.2) and adjust with lime as necessary. Consider making raised beds. Potted irises can benefit from alfalfa pellets and bone meal, bedded irises as well.
Continue planting, remember “good planting rules” with the rhizome’s top exposed to the sun. Monitor for borers and water plants as needed.
This is that exciting time when orders placed earlier will be coming to your mail box. Make permanent labels (CIS sells them) and diagram the plantings for identification in the event a label is misplaced or lost to animal damage. Nothing is more disheartening than to have lovely bloom stalks and no idea of its identity.
In this NC area, we can still plant irises. Squirrels like to dig to hide acorns in newly dug areas, so check that they haven’t dug your plants as well. Fertilize again with a low nitrogen fertilizer, such as 5-10-10. Remove any totally browned foliage.
If you must still be planting, place a rock or brick on the rhizome temporarily to prevent it from heaving in freezing and thawing during the winter. Continue to enjoy re-blooming stalks. Be judicious in removing falling leaves from the plantings.
Enjoy the holidays! Remember, gardening is a compromise with the weather, work when you can. Gardening is therapy mixed with a full dose of passion. Happy New Year!