Chlorosis

Chlorosis is a term used when leaves turn yellow due to iron deficiency.

FARGO — Someday I’ll write a book about the quirky language of gardeners.

Terms that roll off the tongues of experienced gardeners often don’t have exact dictionary definitions, and should be defined so new green thumbers can learn the traditional language, often found in gardening books or heard in gardening discussions.

Many of the terms are almost funny. Do you know your perennials can heave?

Some plants require a rest period, which has nothing to do with an afternoon nap. Although chlorosis sounds like a liver ailment, it’s not.

Following are phrases used by gardeners, especially in late summer and fall.

  • First frost of fall: The first time temperatures in an area dip to 32 degrees. Annual plants that are very temperature-sensitive are killed during this first frost, such as coleus, impatiens and tomato plants. Other plants tolerate the first frost, such as cabbage, broccoli and garden mums.
  • Killing frost: A frost that officially ends the growing season in an area. Temperatures dipping to about 25 to 28 degrees kill most annual flowers and garden vegetable plants and blackens the foliage of most perennial plants. Also often called a “hard freeze.”
  • Fall color: Term used for the change in foliage color of some trees and shrubs, triggered by shortening days and intensified by cool temperatures.
  • Dig and divide in fall: Refers to the best time to move or separate some perennial flowers to relocate, start new ones or for the plant’s health. Peony, bleeding heart, day lily, true lilies and iris are all typically dug and divided in fall, such as September.
  • Chlorosis: Yellowing of foliage, such as that caused by inability of plants like maples to absorb soil iron.
  • Heaving of perennials: Freezing and thawing of the soil during winter or early spring can tear the roots of perennial flowers and lift them out of the soil, exposing roots and causing damage. Prevented by mulching in late October or early November.
  • Rest period: Some plants require downtime often accompanied by withholding moisture, which triggers a regrowth in foliage or flowers. Flowering in amaryllis can be triggered by giving a rest period.
  • Lowest apple harvest temperature: Late-ripening apple varieties can remain on the tree down to 25 degrees. Cool temperatures favor buildup of sugars.
  • Soil freeze-up: When continued fall frosts penetrate the soil, eventually freezing it solid, preventing further digging, planting or other soil work. Varies by season and location, but often happens in early November in much of North Dakota and Minnesota.
  • Dormancy: A period of inactivity of plant growth, caused by temperature or moisture change. Lawns can go dormant during drought. Dormancy in deciduous trees is triggered by cold temperatures and shortening daylength.
  • Dormant pruning: Pruning during a shrub or tree’s inactive period. Most deciduous (leafy) trees and shrubs are best pruned during the dormant period, usually late winter or early spring before new growth begins.
  • Granular fertilizer: Dry fertilizer formulated in small beads, as opposed to liquid fertilizers. Lawns benefit from granular fertilizer applied in September.
  • Exposed location: A spot that receives little protection from the elements and is often windswept and open. Tender perennials do poorly in exposed locations unless extra measures are taken, like mulching.
  • Fall mulch: A layer of straw, leaves or dried grass clippings applied in late fall after soil has frozen, to prevent penetration of extreme winter cold and prevent freezing and thawing caused by fluctuating temperatures. Thickness is usually between 12 and 24 inches.
  • Overseeding: Spreading grass seed over an existing lawn that is thin or damaged. Early September is an excellent time to overseed.

Don Kinzler, a lifelong gardener, is the horticulturist with North Dakota State University Extension for Cass County. Readers can reach him at kinzlerd@casscountynd.gov or call 701-241-5707.

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