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Bulbs Plants with Underground Structures: 

Bulbs Plants with Underground Structures By Cecilia Ritterbush


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 : 

True Bulbs Are underground stem bases containing embryonic plants These are surrounded by scales Modified leaves that overlap each other 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 To divide them, separate these from the mother bulb


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 Formed from the dried bases of previous season’s leaves Each corm lasts for a single year As it shrinks, a new corm, or cormel (small increases) forms on top of it To divide, separate healthy new corms from the old corms Cormels may take 2 to 3 years to reach flowering size


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) in its axil Perennial tubers (i.e.: cyclamen, begonia) increase in size each year Annual tubers (i.e.: potato) disintegrate as new tubers grow To divide either kind, cut it into sections, making sure each has one or more growing points.

Rhizomes : 

Rhizomes A thickened stem growing 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 To divide, cut into sections that have visible growing points

Tuberous Roots : 

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 To divide, cut the root cluster apart so each division contains both roots & part of a stem base with one or more growth buds

Selecting Bulbs : 

Selecting Bulbs Choose plump, firm bulbs that feels heavy for their size AVOID any that are soft, squashy, or shriveled Bulbs are graded by size Larger ones generally yield more flowers, and are more expensive Mass plantings are more economical using midsize bulbs_ they will build up after a year or two and be the size of a large bulb

Planting Bulbs : 

Planting Bulbs They need soil with good drainage For poor drainage soils: plant on a slope or in raised beds Dig an individual hole for each bulb Prepare a complete fertilizer (10-10-10) & work it into the bed or dig up to a tablespoon into the bottom of each hole, then about 2 inches of compost or soil over that, and finally plant the bulb In most soils, true bulbs should be planted about 3 times as deep as the bulb is wide.

Caring for Bulbs : 

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 Scratch the fertilizer into the soil or apply it in narrow trenches dug near the bulbs and water thoroughly

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