spear a thought for asparagus
Asparagus seeds typically germinate
within 10 to 14 days under ideal temperatures between 71 to 79°F. The
seedlings are fairly hardy and although
lower temperatures will slow growth,
the plants can handle cool conditions
and are tolerant of high salinity. As
with many crops grown hydroponically, genetics are vital to ensuring a
good crop and high yields of edible
asparagus. Older varieties of asparagus
are much slower to start cropping than
modern hybrids, are lower yielding and
prone to a number of root rot diseases
and also produce both male and the
less desirable female plants. Most
commercial hybrid asparagus varieties produce all-male plants, as female
plants will at some stage flower and set
fruit (berries), which drains reserves
from the plant crown and lowers the
yield of spears. Female plants, if they do
occur in asparagus plantings, are typically culled as soon as they flower and
are replaced with male plants. Good
hybrids of asparagus that can be grown
from seed include Jersey Supreme F1,
Jersey Knight F, UC157 and the purple
cultivar Purple Passion F1.
After germination, young plants can
be potted into progressively larger containers as they grow and the root system
develops. At this stage, warm conditions
between 75 to 86 oF speeds up the rate
of development of the fern (foliage)
and the young crown. Light levels can
be increased as the plants mature with
intensities similar to those provided to
capsicum or tomato crops applied. At
around 10 months, the plants should
be settled into a deep grow bed or
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Maximum Yield USA | January 2014
“Since asparagus can
be grown in a pot or
container, plants can be
moved outdoors for some
of the year and shifted
back into the heated
indoor garden once
dormant during winter.”
container at least 1-ft. deep, with the
young crown positioned 2 or 3-in.
beneath the surface of the substrate.
A well-balanced vegetative nutrient
solution can be applied throughout the
active growing stage. Recommended
EC levels are in the 2.4 to 3.0 range for
mature plants, although higher levels
can be run for this salinity-tolerant
crop. Asparagus fern can grow quite
tall and may need staking to keep it
contained in small spaces. The older
yellow fern can be cut and removed
as it ages to help maintain air flow
around the base of the plants.
As the plants mature, the spears
(new shoots) sent up from the crown
developing beneath the substrate will
gradually increase in diameter until
they are of edible size. Although the
thin spears of young asparagus plants
can be harvested, it’s best to leave these
to develop into foliage, which in turn
produces assimilate for plant growth.
Try to refrain from harvesting until
the plant is more mature and spear
diameter has increased.
Hydroponic asparagus can be grown in pots, beds or
containers, in either a greenhouse or an indoor garden.
Asparagus plants are easily grown from seed and
mature rapidly under warm growing conditions.
Young, container-grown asparagus crowns ready
to plant out into a hydroponic system.