Vegetative Victory By Terri W. Starman and Kristen L. Eixmann

Growing vegetative annuals can help you gain a competitive edge. Research from Texas A&M shows you how to master bloom time and control growth.

Are you looking for a new potted plant that doesn’tneed pinching or disbudding; a fast crop for hanging baskets; an unusual plantto make your container gardens stand apart from the competition; top-qualityplants that are easy to grow with no major pest or disease problems? Are yourcustomers asking for something new? Try some of the new vegetative annuals.

Among the vegetative annuals, the cultivars are new, neweror newest. Since I started growing vegetative annuals in 1994, each coming yearhas brought new species and cultivars to the market. In the past eight years, Ihave seen cultivars come and go, and every year there is an exponentialincrease in the number of new species and cultivars. This year at the PackTrials in California, growers got a sneak preview of the many exciting newspecies of vegetative annuals that will be on the market next year (see pages24 and 100 for details). So if you haven’t started growing vegetativeannuals, it’s time to start because they are not going away.

Vegetative Basics

Vegetative annuals are a diverse group of plant genera thataren’t necessarily annuals at all. They just bloom their heads off likeannuals. They are also alike in that they are vegetatively propagated. Many ofthese new plants are ones that have been propagated by seed in the past and arenow being cloned, allowing breeders to reproduce sterile cultivars. Plants arethen treated to remove viruses, which gives growers a plant with uniquecharacteristics that produces consistent, high-quality crops. Another commoncharacteristic of vegetative annuals as a group is that they grow and flowerbest under high light intensity. The higher the light intensity, the soonerthey bloom and the more branching and tightly stacked nodes they have.

Although there is not much we can generalize about thisdiverse group of plants, it can be helpful to classify the vegetative annualsinto groups. Figure 1 on pages 58-62 shows some categories of vegetativeannuals that may help you grow them more efficiently and profitably.

Production Guidelines

Temperature preference.Some like it cool, and some like it warm. Breeders have come a long way withbreeding heat tolerance into some genera. Still, even though we can grow thecool plants in the South in the early spring and fall, it’s best not toexpect much from them during the summer. Fall is definitely a time to expandthe use of this group of plants.

Photoperiod preference.Some vegetative annuals are facultative long-day plants, while most others areday neutral. It is wise not to try to efficiently grow the facultative long-dayplants in January and February unless you plan to use night interruptionlighting. The two most common genera of vegetative annuals that bloom fasterunder long days than under short days are calibrachoa and petunia. This iscomplicated by the fact that some cultivars of each genus are morephotoperiod-sensitive than others. For example, we grew calibrachoa’Colorburst Red’ and ‘Million Bells Cherry Pink’ at twodifferent times starting Week 3 and Week 9 and got very different results. Week3 Colorburst Red plants took four weeks longer to be marketable, were threeinches wider and had five less flowers per plant when compared to Week 9plants. Later-grown plants had a more compact, rounded form and a betterdistribution of flowers. This is because the plants grow without flowering whenthe days are short. Week 3 Million Bells Cherry Pink, on the other hand, tookthree weeks longer to finish than Week 9 plants. One difference was the Week 9plants needed three Bonzi sprays at 50 ppm to achieve the same upright formwhile those started Week 3 had no plant growth regulator treatment.

Plant form. Some vegetative annuals are full-figured andstand alone, while others are more slight in build and make better companionplants. The companion plant types are best Á used in mixed containers.Those with fuller form can be grown alone in small pots or in monoculturehanging baskets.

Plant growth regulators.Some vegetative annuals are aggressive, and others are easy to control. Thereally aggressive, trailing cultivars are best grown in hanging baskets late inthe season. Our experience with trying to grow them in 4-inch pots resulted inplants getting too tall or tangled on the bench regardless of the number ortiming of plant growth regulator spray applications. These plants are allcandidates for the newer methods of applying growth regulators, including “linerdips” and “sprenching,” and research is ongoing.

Challenges

The two biggest challenges growers face with vegetativeannuals are: 1) getting an early crop to bloom and 2) keeping a latecrop’s growth under control within a limited bench space. When you lookthrough catalogs to pick and choose the vegetative annuals that are most suitedto your needs, two major management questions need to be asked: 1) when are yougoing to get vegetative annual plugs delivered to your greenhouse, and 2) inwhat size containers will you market the finished product?

Order date.Experiments conducted in the South have proven it would be more profitable toget your vegetative annual plugs for the gardening market to your greenhouse inat least two shipments. We have used Week 3 and Week 9 as ship weeks in ourexperiments. Plants arriving in Week 3 should be those that flower during shortdays with lower light intensity and cooler temperatures. This means they needto be day-neutral in their response to photoperiod and branch, flower andthrive at cooler temperatures.

Week 9 plants grow better when the days are longer, lightintensity is higher and temperatures are warmer. Many of them are facultativelong-day plants in their flowering response to photoperiod. Some vegetativeannuals are very specific and can only be produced of good-enough quality atone time during the spring. Others can be produced either or both timesresulting in the same high quality.

The vegetative annuals listed as “early season” plants(See Table 1, pages 58-62) finished in 7-11 weeks when started Week 3 andtherefore would be good products for the Easter and early spring market. Duringthis time period, we did not need to use plant growth retardants.

Plants started Week 3 were grown at 60° F for two weeksthen 55° F night temperature set points in our greenhouse. Fertilizer waslow ammonium (15-5-15) at 200 ppm, and the pH was maintained at 5.5-6.0 withone application of FeSO4. Plants were not treated with any insecticides. Theyreceived one application of Banrot as a preventative fungicide drench. Mostplants were pinched once.

The vegetative annuals listed as “late-season”plants (See Table 1, pages 58-62) were started in Week 9 and finished in 6-9weeks for the late spring and Mother’s Day market. Some of these plantscould be started even later. Most of these plants required three spraytreatments of Bonzi at 50 ppm at weekly intervals starting 2.5 weeks afterpotting to control their growth so they could be grown in 4-inch pots spacedfour plants per Á square foot. Plants were grown at 65° F nighttemperature set point. Fertilizer was 20-10-20-at-200, later increased to 300ppm, and the pH was maintained at 5.5-6.0. The calibrachoa and petunias got aFeSO4 drench to adjust the pH down and an osmocote application in addition tothe liquid feed. Marathon was used to prevent insect pests, and a Banrotpreventative fungicide drench was applied to prevent root rot.

Container size. Somevegetative annuals are best grown in large containers, and some can be quiteattractive grown in small pots. Therefore, the grower has to decide how tomarket the crop when ordering plugs. Plugs could be directly planted into thefinal container or transplanted on arrival to 4-inch pots and then latertransplanted to a larger container.

 

*It should be noted that all of the vegetative annualslisted in Figure 1 are suitable for use as companion plants in various sizes ofcontainer gardens.

 

The authors would like to thank the companies that donatedplant materials for their experiments.



Terri W. Starman and Kristen L. Eixmann

Terri Starman is associate professor and Kristen Eixmann is research assistant at Texas A&M University. They can be reached at (979) 845-5341 or via E-mail at tstarman@tamu.edu.



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