September 2020 - 50

technically speaking
BY ERIK RUNKLE
How to Produce Poor-Quality
Floriculture Crops
Of course, no one actually intends to produce floriculture
crops that are of poor quality. However, sometimes growers
unknowingly follow practices that can contribute to, or directly
cause, a reduction in crop quality. While there are some tradeoffs
between crop quality and crop timing and/or input costs,
the practices below should be avoided whenever possible.
Hold plants over from last year. It may be tempting to keep
plants that didn't sell, and
hold them over until the
next year. This is
usually not a good
idea; plants may
become infested
with insect pests
(increasing the
potential for virus
transmission),
the pH may drift,
and plant vigor
could decrease.
These plants also
take continued
maintenance
and a favorable
environment,
costing money just to keep the plants alive. Once
Erik Runkle is
professor and
floriculture
Extension specialist
in the department
of horticulture at
Michigan State
University. He can be
reached at runkleer@
msu.edu.
outside, fan louvres and vents that do not properly close allow the
warm air inside to escape, which can increase your fuel bill.
Don't maintain HAF fans. Horizontal air flow (HAF) fans
improve the uniformity of the air (temperature, humidity and
carbon dioxide concentration). Obviously a fan that doesn't work
doesn't serve its function. In addition, fans pointed downward or
upward don't mix the air as intended, which can create uneven
drying conditions of the crop.
Limit light levels during the
Figure 1. Several production challenges can arise when plugs and
liners are held in their containers, such as premature flowering,
which can subsequently reduce crop quality.
the marketing window has closed, cut your losses and dump
the plants.
Let weeds proliferate. By keeping weeds in pots, under
benches, or along the edges of your greenhouse, you're
allowing them to produce seeds that get into your floriculture
crops. They also compete with the planted crop for light, water,
and nutrients, and also harbor insect pests. Cover bare soil in
and around the greenhouse, and routinely remove weeds.
Don't clean your greenhouse. Plant debris, algae, excessive
substrate and other organic materials are great places for plant
pathogens and insect pests to proliferate. I find that there is a
strong correlation between the cleanliness of a greenhouse and
the quality of the crop produced.
Don't scout for insects. Growers should use sticky cards and
routinely (e.g., weekly) check them to monitor pest populations.
Without scouting, it can be difficult to identify insect pressure
until it is already a big problem, which usually necessitates
greater application of pesticides. Scouting is a proactive, not
reactive, way to control insect pests.
Ignore your ventilation system. For many (but not all)
floriculture crops, plant quality decreases as temperature
increases. Insufficient venting (inoperable roof vents) and poorly
maintained exhaust fans allow the greenhouse temperature to rise
excessively in the spring and summer. In addition, when it is cold
50 SEPTEMBER 2020 GPNMAG.COM
winter. The quality of many
crops increases with light
intensity. To improve crop
quality, remove whitewash in
the fall; don't hang baskets
above a crop until at least
March; limit any other
overhead obstructions; use
supplemental lighting from
October through March; and
re-skin poly greenhouses
when they reach their
intended lifetime.
Increase plant density.
Plants have a " shadeavoidance
response " in which
their growth is influenced by perception of their neighbors. As
competition for light increases (at a higher planting density),
extension growth of stems, leaves, and petioles increases. When
plants are widely spaced, they are able to harvest more light on
a per-plant basis and, in response, branch number increases,
stems get thicker and stems elongate less. Of course, trade-offs
with wide spacing, such as greater allocation of overhead per
plant, and less production output, also need to be considered.
Delay transplanting. Plugs and liners are ready for transplant
once they have a sufficient root system to easily be removed
from trays with the substrate intact. If they remain in their trays
longer than intended, several challenges can arise: the substrate
pH can start to drift, plants may initiate flowers prematurely, and
plant vigor can decrease (Figure 1).
Let foliage stay wet. The likelihood of spore germination and
leaf penetration increases as plant leaves stay wet. Therefore,
avoid watering plants after mid-afternoon so that foliage is dry
by sunset.
Don't monitor the pH or EC. One of the most common
production challenges is to maintain desirable fertility and
substrate pH. Both should be measured routinely (e.g., weekly)
with calibrated sensors. Charting these over time can inform
the grower as to whether feed is too high or low, or the pH is
drifting out of range. This information enables growers to make
corrective actions before symptoms become apparent.
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September 2020

Table of Contents for the Digital Edition of September 2020
