Garden Guide: Summer and fall bulbs

Mar. 06, 2013 @ 11:00 AM

The term bulb refers to an underground fleshy storage organ. The term can be slightly confusing since not all bulbs are true bulbs. What? A more “politically correct” term to use would be geophyte, meaning earth plants.   

So why aren’t all bulbs really bulbs? Plants with underground storage organs are divided based on whether the organ resulted from stem or root tissue and on orientation (vertical vs. horizontal). Confusing I know. The important thing to know is that there are true bulbs (daffodils, tulips), corms (gladiolus), tuberous roots (dahlias), rhizomes (irises, cannas), and tubers (caladiums).

Many spring and fall blooming bulbs come from the Mediterranean areas of the world. They have adapted to be underground during the arid summers typical of these areas. Other bulbs originate from temperate woodlands. Still others come from everywhere in between. Bulbs can endure periods of unfavorable weather since they have storage reserves and can withdraw under the soil during adverse conditions.   

When buying bulbs, buy early to get the best selection. Check that bulbs are healthy (they should be a whitish cream) and firm. They should also feel slightly heavy for their size — light bulbs are probably dead already. A general rule to keep in mind is that larger bulbs will have more and/or larger flowers.

Plant summer- or fall-flowering bulbs (NOT daffodils or tulips) in late spring. If you need to store bulbs, use a cool area. A refrigerator is fine, just keep away from ripening fruit. Select a well-draining site with proper sun exposure. In clay soils, incorporate organic matter or plant on raised beds to improve drainage. Dig a hole to the depth noted on the package or set 2.5 times deeper than the diameter. If at all possible orient the roots down. To add interest, plant in odd-numbered groups. You can choose to plant in formal rows or naturalized drifts. In years with drought, use 2-3 inches of mulch to retain moisture.   

Slow release fertilizers work well for bulbs. Incorporate fertilizer into the hole — do not set the bulb on a lump of fertilizer. This will cause the roots to burn.

Some bulbs are not hardy in our area. If the bulb is not hardy (meaning it is hardy in zone 8+), it may need to be lifted come winter. Wait until the foliage begins to yellow, then use a shovel to lift the bulbs. Cut off foliage and allow bulbs to dry completely before storing in paper bags. Place bags in a cool area. Marginally hardy bulbs may be left in the ground with a fall application of 3-4 inches of mulch.   

For recommendations on summer- and fall-blooming bulbs, contact our Center. Bulbs are a great way to plant a lot of color in a small area. And the options are endless!

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