KIWI CORNER 



vinly a few pioneers 

 are using new research 



Show any customer two plants of 

 the same perennial species, one 

 still vegetative and the other in 

 flower, and it would be a rare cus- 

 tomer who shells out more money 

 on foliage than for blooms. Peren- 

 nial plants are a boon for nursery 

 sales and the many available species 

 make for a much more interesting 

 landscape than the old bedding 

 plant standards. While perennials 

 are an increasingly important aspect 

 of our local industry, however, most growers 

 are producing them in a conventional fash- 

 ion — only a few pioneers are using new re- 

 search to force out-of-season flowering on pe- 

 rennials so that plants can be sold in bloom 

 earlier in the spring or summer. 



An exciting aspect of growing any ornamen- 

 tal plant is to learn how to trigger its flower- 

 ing. We are all familiar with fall-blooming 

 poinsettias needing long nights to flower. 

 Many spring- or summer-blooming perennials 

 require some combination of cooling and long 

 days to force a change from vegetative to re- 

 productive growth. 



A lot of research has been coming out of 

 Michigan State University and other universi- 

 ties that has resulted in growing blueprints for 

 perennials. Some of this information has been 

 appearing in Greenhouse Grower magazine, with 

 a different crop being featured each month. 

 The first series has been pulled together in a 

 booklet "Firing Up Perennials" and the current 

 series that just finished will also be available 

 from Meister Publishing (440-942-2000). 



Here at UNH, we are starting to use this 

 information in our teaching of herbaceous 

 landscape plants, so that our students under- 

 stand how to schedule perennials. For example. 

 Campanula carpatica 'Blue Clips' is one of my 

 favorites. This species, with delicate blue (or 

 white for 'White Clips') bell-shaped flowers, 

 makes a beautiful plant in a four-inch con- 

 tainer. The key to flowering of C. carpatica is 

 simply long days of more than 14 hours or a 

 four-hour night interruption, using fluorescent. 



to force 



out-of-season flowering 



incandescent, or high-pressure so- 

 dium lamps. 



If you are finishing plants from 

 plugs, bulk up Campanula under 

 short days for about ten weeks be- 

 fore you start forcing under long 

 days. Flowering occurs nine weeks 

 later to produce a balanced plant 

 for a four-inch pot. 



In contrast, most Aquilegia spe- 

 cies require a ten-week cooling 

 period at 35-45°F to induce flow- 

 ering, after which they are "day-neutral" (i.e. 

 photoperiod will not affect flowering time). If 

 you place Aquilegia under long days without 

 cooling, most species will never bloom. We 

 have modified our greenhouse cooler to be able 

 to provide a low intensity of fluorescent light 

 (25-50 foot-candles) during the cooling period. 

 Aquilegia is an example of a perennial that has 

 a long juvenile stage — plants must reach a 

 critical size before they will respond to cooling 

 or long day treatments. 



Note that every species is different. Some 

 species, for example Coreopsis grandiflora 

 'Sunray,' need both a cold- and long-day treat- 

 ment to flower. Plants, such as Campanula, 

 that simply require long days are easy to force. 

 Plants that require a cold treatment need either 

 a cooler with some artificial light or a mini- 

 mally heated greenhouse that keeps root/crown 

 temperature above 28°F and where heat does 

 not build up during the day. 



This is an exciting development that, for 

 some growers, will create a new type of prod- 

 uct. If you are interested in the topic, check 

 out the Greenhouse Grower articles or attend a 

 greenhouse industry seminar. We thank Van 

 Berkum Nursery for donating some of the Aq- 

 uilegia we are growing. Plugs of Campanula 

 and Coreopsis were donated by C. Rakers and 

 Sons. 



Paul Fisher, Department of Plant Biology, 

 Spaulding Hall G-44, University of New Hampshire, 

 Durham, NH OJS24, can be reached by phone at 

 60^-862-4^2^, by fax at 862-4j^j, or by e-mail at 

 prf@hopper. unh. edu. 



