It's official, Fort Wayne is now in Zone 6, according to the U.S. Department of Agriculture.
The Summit City moves from Zone 5b into Zone 6a, with Huntington.
What does this mean? Well, when you buy plants, you can look at ones that can withstand 10 degrees below zero instead of 15 degrees below zero.
We are just barely over the line, though, so I'm still planning to pick plants that will survive in Minneapolis.
In 2000, we ran a quiz about hardiness written by Lindsay Bond Totten, a horticulturist who writes about gardening for Scripps Howard News Service.
If you want to impress your friends with your hardiness knowledge, I am including the highlights:
1. Cold hardiness depends on: a. root to shoot ration; b. genetic potential; c. amount of chlorophyll produced late in season; d. environment. Answer: b. and d. Winter hardiness is established by a plant's genetic makeup, but its ability to withstand cold is strongly influenced by environmental cues and cultural conditions.
2. What triggers a plant to begin going dormant in preparation for winter? a. shorter day lengths; b. less moisture in late summer; c. leaves beginning to change color; d. cooler nighttime temperatures. Answer: a. Plants initiate the hardening process in response to day length. The gradual process of going dormant begins as days get shorter in late summer, even though temperatures may still be very warm. Later, cooler temperatures trigger the second stage of hardening, a complex reaction involving the production of enzymes and carbohydrates. Seven days of exposure to near-freezing temperatures quickly shuts down all systems.
3. Roots are hardier than twigs and buds. True or false? Answer: False. Roots are substantially less hardy than above-ground parts. Roots of hardy plants never go completely dormant, so they're more sensitive to cold than twigs and buds. Also, mature roots are hardier than new young roots. Compare the temperatures at which young roots and mature roots of several common plants are killed: burning bush (Euonymus alatus "Compacta"), 19 degrees (young), 7 degrees (mature); American dogwood (Cornus florida), 21 degrees (young, 10 degrees (mature); Hicks yew (Taxus x media "Hicksii"), 18 degrees (young), minus 4 degrees (mature). Lack of root hardiness is what prevents most trees and shrubs from surviving the winter in pots. Best bets for above-ground containers are Siberian peashrub, yew, juniper, mugo pine, dwarf Alberta spruce and amur maple.
4. What substance is most responsible for plant cold hardiness? a. alcohol; b. water; c. sugar; d. essential oils. Answer: c. It's the concentration of sugars, or carbohydrates, within a plant's cells that prevents the formation of ice crystals and enables cells to withstand freezing temperatures without rupturing.
5. Where a plant comes from (e.g. a northern nursery vs. a southern nursery), has a lot to do with how hardy it will be. True or False? Answer: True. Provenance, or native range, makes a big difference in how well a plant acclimates to its new home. Especially critical is the first winter. A southern-grown plant, propagated from similar stock, is likely to be less hardy than a northern-grown specimen of the same species its whole life.
6. Red osier dogwood (Cornus stolonifera) is one of the hardiest deciduous shrubs. Twigs can survive what temperature? a. minus 50 degrees; b. minus 85 degrees; c. minus 100 degrees; d. minus 300 degrees? Answer: d. Believe it or not, red osier dogwood stems can survive temperatures slightly colder than 300 degrees below zero.
7. Which of the following play(s) a role in plant hardiness? a. lack of moisture due to drought or frozen soil; b. snow cover; c. drying winds; d. a freeze-thaw cycle in mid winter; e. a late freeze in spring. Answer: All of the above. Cultural conditions play a significant role in plant hardiness. Drought and drying winter winds are especially hard on evergreens. Any one of the above could explain the death of a plant.
8. The age of a plant plays a role in its hardiness. True or False? Answer: True. Young plants are more susceptible to cold injury than mature plants. New shoots are also more tender than older shoots, explaining why the new growth that results from a late-season pruning of boxwood or yew, for instance, dies during the winter while the older foliage is fine.
9. Gardeners shouldn't try to grow plants outside of their hardiness zone; doing so could weaken the species. True or false? Answer: False. We wouldn't be telling the truth if we didn't admit to a fair amount of zone denial. That's what microclimates are for.