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’t
need pinching or disbudding; a fast crop for hanging baskets; an unusual plant
to make your container gardens stand apart from the competition; top-quality
plants that are easy to grow with no major pest or disease problems? Are your
customers asking for something new? Try some of the new vegetative annuals.
Among the vegetative annuals, the cultivars are new, newer
or newest. Since I started growing vegetative annuals in 1994, each coming year
has brought new species and cultivars to the market. In the past eight years, I
have seen cultivars come and go, and every year there is an exponential
increase in the number of new species and cultivars. This year at the Pack
Trials in California, growers got a sneak preview of the many exciting new
species of vegetative annuals that will be on the market next year (see pages
24 and 100 for details). So if you haven’t started growing vegetative
annuals, it’s time to start because they are not going away.
Vegetative annuals are a diverse group of plant genera that
aren’t necessarily annuals at all. They just bloom their heads off like
annuals. They are also alike in that they are vegetatively propagated. Many of
these new plants are ones that have been propagated by seed in the past and are
now being cloned, allowing breeders to reproduce sterile cultivars. Plants are
then treated to remove viruses, which gives growers a plant with unique
characteristics that produces consistent, high-quality crops. Another common
characteristic of vegetative annuals as a group is that they grow and flower
best under high light intensity. The higher the light intensity, the sooner
they bloom and the more branching and tightly stacked nodes they have.
Although there is not much we can generalize about this
diverse group of plants, it can be helpful to classify the vegetative annuals
into groups. Figure 1 on pages 58-62 shows some categories of vegetative
annuals that may help you grow them more efficiently and profitably.
Some like it cool, and some like it warm. Breeders have come a long way with
breeding heat tolerance into some genera. Still, even though we can grow the
cool plants in the South in the early spring and fall, it’s best not to
expect much from them during the summer. Fall is definitely a time to expand
the use of this group of plants.
Some vegetative annuals are facultative long-day plants, while most others are
day neutral. It is wise not to try to efficiently grow the facultative long-day
plants in January and February unless you plan to use night interruption
lighting. The two most common genera of vegetative annuals that bloom faster
under long days than under short days are calibrachoa and petunia. This is
complicated by the fact that some cultivars of each genus are more
photoperiod-sensitive than others. For example, we grew calibrachoa
‘Colorburst Red’ and ‘Million Bells Cherry Pink’ at two
different times starting Week 3 and Week 9 and got very different results. Week
3 Colorburst Red plants took four weeks longer to be marketable, were three
inches wider and had five less flowers per plant when compared to Week 9
plants. Later-grown plants had a more compact, rounded form and a better
distribution of flowers. This is because the plants grow without flowering when
the days are short. Week 3 Million Bells Cherry Pink, on the other hand, took
three weeks longer to finish than Week 9 plants. One difference was the Week 9
plants needed three Bonzi sprays at 50 ppm to achieve the same upright form
while those started Week 3 had no plant growth regulator treatment. style="mso-spacerun: yes">
Plant form. Some vegetative annuals are full-figured and
stand alone, while others are more slight in build and make better companion
plants. The companion plant types are best Á used in mixed containers.
Those with fuller form can be grown alone in small pots or in monoculture
Plant growth regulators.
Some vegetative annuals are aggressive, and others are easy to control. The
really aggressive, trailing cultivars are best grown in hanging baskets late in
the season. Our experience with trying to grow them in 4-inch pots resulted in
plants getting too tall or tangled on the bench regardless of the number or
timing of plant growth regulator spray applications. These plants are all
candidates for the newer methods of applying growth regulators, including “liner
dips” and “sprenching,” and research is ongoing.
The two biggest challenges growers face with vegetative
annuals are: 1) getting an early crop to bloom and 2) keeping a late
crop’s growth under control within a limited bench space. When you look
through catalogs to pick and choose the vegetative annuals that are most suited
to your needs, two major management questions need to be asked: 1) when are you
going to get vegetative annual plugs delivered to your greenhouse, and 2) in
what size containers will you market the finished product?
Experiments conducted in the South have proven it would be more profitable to
get your vegetative annual plugs for the gardening market to your greenhouse in
at least two shipments. We have used Week 3 and Week 9 as ship weeks in our
experiments. Plants arriving in Week 3 should be those that flower during short
days with lower light intensity and cooler temperatures. This means they need
to be day-neutral in their response to photoperiod and branch, flower and
thrive at cooler temperatures.
Week 9 plants grow better when the days are longer, light
intensity is higher and temperatures are warmer. Many of them are facultative
long-day plants in their flowering response to photoperiod. Some vegetative
annuals are very specific and can only be produced of good-enough quality at
one time during the spring. Others can be produced either or both times
resulting 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 and
therefore would be good products for the Easter and early spring market. During
this time period, we did not need to use plant growth retardants.
Plants started Week 3 were grown at 60° F for two weeks
then 55° F night temperature set points in our greenhouse. Fertilizer was
low ammonium (15-5-15) at 200 ppm, and the pH was maintained at 5.5-6.0 with
one application of FeSO4. Plants were not treated with any insecticides. They
received one application of Banrot as a preventative fungicide drench. Most
plants 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 6-9
weeks for the late spring and Mother’s Day market. Some of these plants
could be started even later. Most of these plants required three spray
treatments of Bonzi at 50 ppm at weekly intervals starting 2.5 weeks after
potting to control their growth so they could be grown in 4-inch pots spaced
four plants per Á square foot. Plants were grown at 65° F night
temperature set point. Fertilizer was 20-10-20 at 200, later increased to 300
ppm, and the pH was maintained at 5.5-6.0. The calibrachoa and petunias got a
FeSO4 drench to adjust the pH down and an osmocote application in addition to
the liquid feed. Marathon was used to prevent insect pests, and a Banrot
preventative fungicide drench was applied to prevent root rot.
Container size. Some
vegetative annuals are best grown in large containers, and some can be quite
attractive grown in small pots. Therefore, the grower has to decide how to
market the crop when ordering plugs. Plugs could be directly planted into the
final container or transplanted on arrival to 4-inch pots and then later
transplanted to a larger container.
*It should be noted that all of the vegetative annuals
listed in Figure 1 are suitable for use as companion plants in various sizes of
The authors would like to thank the companies that donated
plant materials for their experiments.