trends & technology
Substrates for Subterranean Crops
Garlic can be grown hydroponically
provided the correct day length is
provided to induce bulb formation.
“GROWING root, tuber,
and bulb crops hydroponically
requires a little more attention to the physical
properties of the substrate than many other plants.”
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grow cycle
Growing root, tuber, and bulb crops hydroponically
requires a little more attention to the physical properties
of the substrate than many other plants. The rapidly
expanding carrot and parsnip tap roots can become
deformed if the growing medium contains large, hard
particles. For perfectly tapered roots, a finer grade of
coconut fiber is ideal. Baby beet, turnip, and bulb onions
perform well in combinations of fine-grade vermiculite
and granulated coconut fiber, which allow for perfectly
rounded specimens to rapidly develop under high-density
planting. When growing bulb, tuber, and root crops in
deep beds or containers, a layered substrate is often the
most successful. This consists of a coarse, free-draining
substrate in the bottom third of the growing bed for feeder
roots to develop into, with a finer, softer medium in the top
two-thirds to support the edible portion of the plant. This
ensures optimal drainage while maintaining sufficient
oxygenation around the roots and a finer surface
substrate layer for perfect tuber or bulb formation.
Nutrient application for root and tuber crops
needs to be evenly distributed. Drip irrigation
systems need to be well-designed, with
drippers placed at regular intervals and
a slow and frequent application
rate. This way the nutrient
solution thoroughly wets the
growing surface, which is
vital during the early stages
of growth. Aeroponics, with
frequent misting of the root
system, is another method of
nutrient application suited
to tuber crops. Nutrients for
root crops require a well-
balanced formulation. Most
general-purpose nutrient
concentrates are suitable. EC
levels are dependent on the
stage of development. For most
tuber, root, and bulb crops,
these are typically run at
1-1.4 mScm -1 in the early
seedling stage and up to 2-2.2
when approaching maturity.
Optimal pH levels are 5.8-6.2.
Diversifying into a few tuber, root, or bulb crops is an
exciting way of extending the range of edibles in an
indoor garden. They don’t need to be dull or mundane
as there now exists an exciting range of highly colored,
unusual, and heirloom types to choose from. Obtaining
the right substrate, ensuring uniform application of nutri-
ents, and dialing in the correct growing environment all
ensure the success of these subterranean crops.