Transcript True Bulbs Corms Tubers Rhizomes Tuberous

Bulbs
Plants with Underground Structures
Bulbs are plants with underground structures
 Serve as storage organs
 Accumulate nutrient reserves for plant survival
through dormancy
 Supply energy for its growth & bloom during the
upcoming year
Five types of bulbs:
True Bulbs
Corms
Tubers
Rhizomes
Tuberous Roots
True Bulbs

Underground stem that contains embryonic plant inside

These are surrounded by scales


Modified leaves that overlap each other (protects embryo)
A basal plate at the bottom of the bulb holds the
scales together and produces roots

Protective papery outer skin called a tunic

Most of them produce offsets/increases

Division- separate these
from the mother bulb
Common True Bulbs
Daffodils
Tulip
Hyacinth
Corms

A swollen underground stem base, it’s composed
of solid tissue rather than scales

Roots grow from a basal plate at the corm’s
bottom; the growth point is at the top

Corms have a tunic

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Each corm lasts for a single year


Formed from the dried bases of previous season’s leaves
As it shrinks, a new corm, or cormel (small increases) forms on top
of it
Division- separate healthy new corms from the old
corms

Cormels may take 2 to 3 years to reach flowering size
Common Corms
Gladiolus
Crocus
Tubers

Similar to corms, they are swollen underground
stem bases, but lack the corms organization

There is no basal plate, so roots can grow from all
sides

A tuber has multiple growth points scattered over its surface


Each is a scale-like leaf with a growth bud (eye)
Perennial tubers (i.e.: cyclamen, begonia) increase in size each
year

Annual tubers (i.e.: potato) disintegrate as new tubers grow

Division of either kind- cut it into sections, making sure each has
one or more growing points.
Common Tubers
Cyclamen
Potato
Rhizomes

A thickened stem growing horizontally
partially or entirely below ground

Its roots grow directly from the underside

The primary growing point is at one end of the rhizome


Additional growing points form along the sides
Division- cut into sections that have visible growing points
Common Rhizomes
Bearded Iris
Bamboo
Tuberous Roots

A true root, thickened to store nutrients

Fibrous roots for the uptake of water & nutrients develop
from its sides & tip

Tuberous roots grow in a cluster


Swollen portions radiate out from a central point
Growth buds are at the bases of old stems rather than
on the roots themselves

Division- cut the root cluster apart so each division
contains both roots & part of a stem base with one or
more growth buds
Common Tuberous Roots
Dahlia
Day Lily
Where do you buy bulbs?
Retail nurseries
(Home Depot, Green Arrow)
Mail order catalogs
On-line resources
Buying Bulbs
• Bulbs should be bought and planted during
the dormant period
Dormant period: the time period when
plants are not actively growing (growth is
slowed down – usually during winter)
• Dormant bulbs will not
have leaves or roots.
Selecting Bulbs

Choose plump, firm bulbs that feels heavy for their size

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AVOID any that are soft, squashy, or shriveled
Bulbs are graded by size

Larger ones usually yield more flowers,
and are more expensive

Planting many bulbs over a large area for bigger effect
earlier (Massing) is more economical using midsize
bulbs- they will build up after a year or two and be the
size of a large bulb
Planting Bulbs

They need soil with good drainage (otherwise
roots will drown and the bulb will rot)

For poor drainage soils: plant on a slope or
in raised beds

Dig an individual hole for each bulb

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Prepare a complete fertilizer (10-10-10)
In most soils, true bulbs should be planted about 3 times as
deep as the bulb is wide.
Caring for Bulbs

Water them while they are actively growing

This period begins after planting & continues until the
foliage dies back, and flowering is finished

Water deeply enough to penetrate the root zone; roots
grow beneath the bulb

At the beginning of growth, a high-nitrogen
fertilizer needs to be applied to enhance the quality
of the current season’s flowers

After the bloom ends it is important to leave the leaves in
tact with the plant until they turn yellow & can be easily
removed

This is the time when the bulb replenishes the nutrients for
the next growing season

Once flowering is finished another application of a
complete fertilizer is important, 10-10-10 or “bulb food”
high in phosphorus and potassium

These two nutrients must reach the root zone to be effective