Improving Plant Quality in Annuals and Perennials with concise™ Excellence in PGR technology Contents 4-13 Concise Use Considerations 14-25 Photo Guide of Growth Regulation with concise 26-33 Recommended Rates for concise Use with Floricultural Crops in Greenhouses 34-41 Growth control of herbaceous perennials with uniconazole 42 PGR Application Record Edited by Dr. Joyce Latimer, Virginia Tech and Dr. Brian Whipker, North Carolina State University. Plant growth regulators (PGRs) are valuable production tools that can be used to enhance the quality and marketability of many ornamental crops. PGRs are chemicals that are designed to affect plant growth and/or development, and although there is much scientific information available on using PGRs in floriculture, it is not an exact science. Achieving the best results with PGRs is a combination of art and science — science tempered with a lot of trial and error and a good understanding of which PGR to use to produce the highest quality crop. Concise“ is an effective growth regulator for use on This guide provides information on concise from a broad variety of annual and perennial crops; from studies conducted by Dr. Joyce Latimer at Virginia bedding and potted plants to woody ornamentals Tech and Dr. Brian Whipker at North Carolina State to bulb crops. Concise contains the active University. Its main purpose is to provide growers ingredient uniconazole-p, a triazole plant growth with general guidelines on use rates for a broad regulator that inhibits the production of gibberellins, range of crops. Keep in mind however, that the the primary plant hormones responsible for cell multitude of variations possible in application elongation. Concise reduces plant height by limiting methods, cultivar and species grown, and in internode elongation, producing more desirable, growing conditions make it impossible to compact and marketable plants. Concise has been recommend specific rates for all operations. shown to increase the quality of plants even in the Determining the correct rate of concise starts with absence of noticeable growth reduction. These referring to the label for the recommended rate for desirable qualities include darker colors, higher the plant you wish to treat and conducting your chlorophyll content, greater leaf thickness, stronger own trials. stems, increased water retention and, at times, increased flower number and size. 4 CONCISE USE CONSIDERATIONS Concise Use Considerations Joyce G. Latimer Extension Specialist, Greenhouse Crops, Virginia Tech, Blacksburg, VA,and Brian E. Whipker Floriculture Research and Extension, North Carolina State University, Raleigh, NC Plant growth regulators (PGRs) are chemicals that are designed to affect plant growth and/or development. They are applied for specific purposes to affect specific plant responses. Although there is much scientific information on using PGRs in the greenhouse, it is not an exact science. Achieving the best results with PGRs is a combination of art and science — science tempered with a lot of trial and error and a good understanding of plant growth and development. Concise (uniconazole, Fine Americas, Inc.) is a Undesirable stretching due to high temperature or plant growth regulator used in the greenhouse and low light conditions can be a production reality. nursery to regulate shoot growth of bedding plants, Growers must be prepared to prevent excessive garden mums, poinsettias, herbaceous perennials, stem elongation. Concise is an excellent tool for bulb crops, woody ornamentals, and other chemical control of excessive plant growth. PGRs containerized crops. Concise reduces elongation can be used in conjunction with a number of of stem, petiole and flower stalk tissues. Lesser non-chemical control options to manipulate plant effects are seen in reductions of leaf expansion, growth so well-proportioned, compact plants can resulting in thicker leaves with darker green color. be produced. Other benefits of using concise in plant production Biological Control include improved plant appearance Selecting shorter growing cultivars is often the first by maintaining plant size and shape in proportion step available to growers for reducing the with the pot. Concise also increases the stress occurrence of overgrown plants. While this works tolerance of plants, which improves their tolerance well in theory, it may not be commercially practical. to shipping and handling and retail marketing, Many customers demand specific color or growth e.g., improving shelf-life and extending form characteristics and shorter growing cultivars plant marketability. with these attributes may not be available. Optimizing Results Therefore, physical or chemical control strategies For best results, PGRs should be handled as must also be incorporated into a production plan. production tools, like water and fertilizer. They Be aware that cultivars of the same species may should not be used as crutches for poor respond differently to concise applications. More management of other cultural practices. PGRs vigorous cultivars will require higher rates of should be an integrated part of your crop concise for optimal height control than dwarf or production cycle. They are most effective when slower growing cultivars. applied at the appropriate times to regulate plant Environmental and Cultural Control growth or development. In other words, growth Knowing how the growing environment and retardants cannot shrink an overgrown plant. cultural practices can affect plant growth will help in PGRs like concise must be applied before the managing a crops growth. There are a number of plant is overgrown to reduce plant stretch. CONCISE USE CONSIDERATIONS 5 factors that can be manipulated in the greenhouse or nursery to reduce plant growth: container size, timing of transplant or seeding, irrigation practices, nutrient management, mechanical conditioning, light quality and quantity, pinching, and temperature. How these factors are manipulated will affect whether chemical control is necessary for optimum growth control and the amount of PGR required. Container Size. The use of root restriction can be used to control plant growth. This is done by utilizing a small container or by increasing the number of plants per pot. This method works especially well when other production parameters wet. The method of irrigation can affect the plant such as ample light, i.e., wide spacing, and proper response to concise. Plants grown on nutrition are provided. Plants grown in small pots at sub-irrigation trays or water collectors should be close spacing will require more concise for treated with lower rates of concise since the adequate growth control than those receiving overspray from the treatment will be available to the ample light. roots during subsequent irrigation events. Timing. One of the most effective methods of Nutrient Management. Reducing or withholding controlling excessive plant growth is by crop fertilizer tends to slow overall plant growth. Limiting timing. The simple method of staggering the finish the amount of nitrogen to 50 to 100 ppm N will time of a crop at 2 to 3 week intervals is very help control growth of many crops such as effective with many crops like bedding plants. This bedding plants. The type of nitrogen supplied ensures that a new supply of plants will always be can also impact plant growth. Relying on available; thus avoiding the need to hold a crop nitrate-nitrogen instead of ammoniacal-nitrogen or which can become leggy. urea-nitrogen forms (which encourage lush growth) will also help. Phosphorus also promotes plant Irrigation Practices. A traditional method of growth. Plug producers commonly use low controlling plant growth is to withhold water. phosphorus fertilizers like 13-2-13 Cal-Mag¤ or Drought stress can be used on a number of crops, 15-0-15 which does not contain phosphorus to including impatiens and tomatoes. Allow the plants help limit stem elongation. As with dry plants, to wilt slightly between irrigations, but do not allow nutrient-deficient plants require less concise for them to reach the permanent wilting point. Drought growth control than lush plants. stress will lead to shorter plants, but excessive stress or drought stress of sensitive crops may Mechanical Conditioning. Brushing plants is a have the undesirable effects of reduced plant very effective way of controlling plant height quality and delayed flowering. Drought stress also (30% to 50% reductions) of many vegetable may cause premature bolting of some crops such transplants or herbs. This is especially important for as ornamental cabbage and kale (cole crops). these crops since no chemical control measures Growers who tend to run their plants dry will use are available. Brushing involves the movement of a less concise than growers who run their plants PVC pipe, wooden dowel rod, or burlap bags 6 CONCISE USE CONSIDERATIONS over the top third of the plant. Researchers at the Temperatures. Temperature manipulation can be University of Georgia suggest that the plants used very effectively to control plant growth. Lower should be brushed daily for about 40 strokes to temperatures reduce plant growth. Remember to obtain the greatest effect. The foliage should be dry account for the effects of lower temperatures on to avoid damage to the leaves. This method is not the developmental processes of the plant, i.e., effective on plants such as cabbage or broccoli lower temperatures may delay flowering so you and should not be used if foliar diseases, or, in may need