June 2020 - 9

MSUE VEGETABLE NOTES
Tips for planting table beets at the proper spacing, depth
By Dan Brainard and Daniel Priddy
MSU Department of Horticulture
Planting table beets at the
appropriate spacing and depth is
important for producing marketable
roots of desirable sizes. Unfortunately,
choosing the best seed rate is challenging
for beets, because varieties differ in
the number of seedlings produced
per seedball (the " sprout count " ) and
because optimal plant densities vary
depending on the market and the
desired size of beet.
Based on these factors, recommended
spacings can vary by a factor of 10
(Table 1). The purpose of this note is to
help you sort out the best seed rate for
your situation so you can improve your
chances of getting the right size beet
without having to resort to expensive
hand-thinning.
Multigerm beets and sprout
counts. Although several " monogerm "
cultivars are available, most table beet
cultivars have " multigerm " seedballs,
meaning that each seedball is actually a
seed cluster containing 0-4 germinable
embryos. Seed clusters are formed
by aggregate beet flowers, and the
number of germinable embryos within
a cluster (= sprout count) varies by
cultivar and seedlot.
Where to get sprout count
information? Some seed companies
provide sprout count information on
their seed bags, but others do not.
If this information is not provided,
you can mimic what is done at seed
testing laboratories, by sowing 50
seedballs at three-fourths-inch depth
in a container filled with sand. Press
the sand firmly and keep moist (but
not too wet) and at room temperature
(~68˚F). After 10 days, count the
number of emerged seedlings and
calculate the sprout count by dividing
the number of sprouted seedlings by
50 (e.g., if you counted 75 seedlings,
your sprout count is 75/50 = 1.5).
Adjusting sprout count for field
conditions. Because field conditions
are generally more challenging than
those in sand in a lab (or your house),
the sprout count usually overestimates
how many seedlings you'll actually
get. Therefore, a " field factor " of 0.60.8
is used to adjust (implying that
only 60-80% of the seedlings observed
in the sprout test will come up in
the field). In our table, we assumed
a field factor of 0.7 to calculate the
" adjusted sprout count. " This 0.7 field
factor was suggested by researchers at
Cornell University who developed the
sprout count methodology (roughly
as described above) in the 60s and
compared sprout counts to field
emergence of fungicide treated seeds
in a silt-loam soil. However, note that
if you are using untreated seeds and
planting into cold wet soil (conditions
that favor pythium and other fungi
that will reduce emergence) you
might want to use a field factor of 0.6
or lower (and bump your seed rate
above what is shown in the table).
Calculating seeding rate. To
calculate the recommended number
of seedballs per row-foot you must
divide your desired plant population
(plants per row foot) by the field
adjusted sprout count (sprout count
x field factor). This is done for you
in Table 1, which provides suggested
seedball rates for a range of desired
beet sizes (small-large) and for sprout
counts ranging from 1.0-1.8. For
example, if your desired plant spacing
is 12 plants per row foot (typical
recommendation for medium sized
beets) and you have a beet cultivar
with a sprout count of 1.8, your field
adjusted sprout count would be 1.26
(1.8 x 0.7 field factor), and you'd need
to plant about 10 seedballs per foot
(12 divided by 1.26 = 9.52). If you are
an organic grower planting untreated
seeds you might bump that up 1020%
to perhaps 12 seedballs per foot.
How deep to plant table beets. In
addition to planting seedballs at
the right density, planting at the
right depth is helpful for improving
stand establishment. For example,
our research group at Michigan
State University planted seedballs of
four cultivars at 1,2,3 and 4 cm (1/31½
inches) depths and monitored
the number of seedlings emerging
over time. Our results demonstrate
large variation in both sprout
counts and sensitivity to planting
depth (Figure 1).
For example, our seedlots of
multigerm varieties had sprout
counts between 1.4 (Boro) to 2.0
(Touchstone Gold) and tolerated a
fairly wide range of planting depths,
with the optimal depth about
three-fourths inch. In contrast, the
monogerm cultivar " Moneta " had
a sprout count of 1.0 (as expected)
and did best when planted less deep.
As a rule of thumb, plant multigerm
beets at three-fourths inch. If there
is better moisture a bit deeper, you
can go to 1 inch, but the number of
seedlings emerging is likely to drop
(see Figure 1), so you might want to
bump your seed rate up a bit more.
In summary, obtaining desired beet
densities in the field is challenging.
To reduce your risk of having stands
that are either too thin or too thick,
use Table 1 to determine your
optimum seedball density, and adjust
your planter to place seedballs at the
desired spacing and depth. If you have
questions or comments, we'd love to
hear from you.
Dan Brainard can be reached at
brainar9@msu.edu and Daniel Priddy can
be reached at priddyda@msu.edu. VGN
Figure 1. Beets vary in the number of seedings produced per seedball ( " sprout count " ), as
well as their sensitivity to planting depth.
VGN | JUNE 2020 | 9
Table 1. Seeding rate guidelines for table beets based on desired beet size (beet-large),
sprout count (1-1.8) and field adjustment factor (0.7).
*Growers typically multiply sprout counts by a field adjustment factor 0.6-0.8 (since not all
sprouts will come up in the filed). For untreated seeds, or challenging soil conditions use a
lower adjustment factor (higher seed rate).

June 2020

Table of Contents for the Digital Edition of June 2020