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Annual Growing Season Summary for the Georgeson Botanical Garden, Tanana Valley, Alaska


The 2013 growing season was certainly one of the oddest weather events we have seen at the GBG in the past 30 years. Our plant sale on May 16 was held in the midst of a nasty snow/rain storm with bitterly cold weather and lots of wind. The very next week, temperatures shot straight up into the 80s, and the heat lingered nearly all summer. We gardeners baked in the sweltering summer heat! Rainfall was scarce, so irrigation was critical to any farming success. Most notably, hay growers experienced yields that were half or more what they usually are both in the Fairbanks and Delta areas. The hillside east of the Garden was seeded twice with barley, and it headed out when it was less than 12 inches tall. One morning there were ravens hopping around the field, and the sad state was, the ravens were taller than the barley!

The radical change in temperatures in spring meant that the usual up and down freeze and thaw that usually lasts through May, did not happen. All plants were delayed several weeks, but when the heat came, they blasted out of their winter dormancy. Most native plants did not show any delay in maturity because of the odd spring. Berries, both cultivated and wild were absolutely prolific probably because of no spring frost damage and abundant pollinators.

The season was short, only 95 days between frosts (May 22, Aug 25), but intense. Rainfall was in short supply, only 5.42 inches with most of that occurring in late August. Growers who irrigated did very well. Some sensitive crops such as spinach and Chinese cabbage bolted easily.


The 2012 growing season had frost free season of 104 days, the shortest since 1997.  From 2006 to 2011, frost occured in late September, providing a long, warm Indian Summer. Not so this year when frost was severe (25F), cutting short many gardens around the Tanana Valley. The season was cooler than the average thaw-degree day accumulation for the past decade.  Growers had few complaints about the season except for it shortness. Wild berry yields throughout the Valley were fair.

Precipitation between May 1 and September 30 was 7.71 inches.  Precipitation was below normal in July, August and September, and irrigation was beneficial for most market gardens around the Interior.


The growing season lasted 129 days (last frost May 17 – first frost September 21). The average temperature in May was the second warmest in the past ten years, reaching a high of 81 degrees F on May 28. Temperatures and precipitation in June were close to normal. July temperatures were normal,
however precipitation was 1.6 inches above average. August temperatures were 2.8 degrees F above normal and reached a record breaking daily high on August 15. September averages were 2 degrees F above normal for temperature and .21" less precipitation than normal

The wet weather in July promoted an outbreak of Sclerotinia (cottony rot), which can be a problem in wetter years when no fungicide is applied. The fungus hit the petunias particularly hard, and many were removed from the garden earlyin the season to prevent further spread of the disease. Ornamentals that were not diseased offered beautiful displays throughout the extended season and all vegetable crops grew well. Overall, 2010 offered a long prolific season at the Garden and around much of the Tanana Valley. It was a pretty good wild blueberry year in the Valley


Although the 2009 season seemed quite warm, it was only the fifth warmest since 1999 (based on thaw degree days). However, The growing season of 126 days was 11 days longer than the 30-year mean. May started with a record high of 76°F and was warmer than normal. June was about average while July had the highest average daily maximum temperature and the lowest precipitation ever recorded in Fairbanks. The high temperatures combined with the drought enhanced area wildfires resulting in heavy smoke in the area for much of the latter half of July. August had cooler temperatures and increased rainfall which alleviated wildfire threats.  September’s mean temperatures were about 4° above the long term mean.

The good weather was not without its drawbacks for both people (smoke) and plants (pests). The warmer than usual weather in May and July promoted a population explosion among insect pests, and aphids in particular decimated eggplants, pepper, and delphiniums.

Voles were a major problem throughout the Interior, and they caused more damage in the garden than we have seen in 30 years. The entire pea crop was destroyed along with some peppers, artichokes, herbs and several annual flower bedding plants that were devoured in flats before they had a chance to be planted. Despite a healthy population of least weasels in the garden, the voles outnumbered them in this warm season.

2008 The summer was cool and overcast especially July through September with average daily maximum and minimum temperatures cooler than the previous two years. The total thaw degree days ranked the 2008 season the third coldest since 1998 in total heat accumulation
during the growing season. Plot evaluations began immediately after planting and continued
weekly through September. They consisted of flowering dates and occurrence of disease, insect pests, seed pods, off-type plants, and deformities. From 10 Aug to 25 Aug, each cultivar was measured for plant height and flower size, rated for performance of flowers and foliage, and evaluated for fragrance and potential use as cut flowers or in dried arrangements. Frost tolerance was noted on September 19, 2008. Each cultivar grown in
the garden beds is tested for at least three years depending upon the availability of seed or plugs. Most ornamentals grew well except for those such as cardoon, castor beans, amaranth, and impatiens that only perform well in very warm seasons. Cool season vegetables grew well, but warm season ones had disappointing yields. Sweet corn did not mature. Gardeners around the Tanana Valley complained of size and quantity reductions in flowers, fruits and vegetables, and delayed ripening especially in those crops requiring warm seasons. Although it was not a record breaking season, 2008 certainly was not one to brag about.
2007 The summer was warm, especially August which was the second warmest August in the past 10 years. The total thaw degree days ranked the 2007 season third in total heat accumulation during the growing season, second in the number of frost free days and first in rainfall. Precipitation was lowest in May and highest in July. The growing season was warm, with sufficient moisture to make irrigation unnecessary except in May and early June during planting and a few days in late August. Growers across the Tanana Valley reported good growing conditions for most flowers and vegetables with the added benefit of no forest fire smoke and very few mosquitoes! The length of the growing season was eclipsed only by the 2001 season mostly because of a long, warm September.
2006 The summer was an average growing season when comparing summary statistics, but it was anything but ordinary. A hard freeze and blizzard on 4 - 5 June caused significant damage to tender annuals. Although only three cultivars were killed, the most tender flowers (i.e. zinnias, marigolds, salvia) showed damage to leaves and flower buds. The official temperature at the weather station reached 30°F, but temperatures at plant level in the plots was 25°F. Plots were covered with Reemay® spun bonded fabric and irrigated overhead to minimize damage. The total thaw degree days showed an average summer only because September was warm and frost was not recorded until the end of the month. Most of the monthly averages were lower than the previous two years. Rainfall was similar to previous years, but much of July and August were overcast. In July, there were 22 continuous days of measurable precipitation.
2005 The summer was long and hot similar to the previous growing season. The last frost occurred in early May leading to one of the longest growing seasons in recent years. A typical drop in temperatures the first week of September ended the season for many flowers, but others continued to bloom through a balmy September. Despite the great early season weather, data on flowering and flower performance were similar to most years because planting did not commence earlier. Gardeners who plant early were treated to at least two extra weeks of blooms.

The last spring frost was 8 May (30°F, -1°C). The amount of precipitation was 3.3 inches below the past ten year average of 8.4 inches. More than half of the rainfall occurring in May and September. The season was the driest in the past ten years. The thaw degree-day accumulation was 475 degree-days higher than the previous ten-year average and was the warmest during the past ten years. The frost free season of 119 days compared to the previous ten year average of 110 days.

The summer was hot, dry and extremely smoky from a record acreage burned by forest fires. The extra warmth provided one of the best growing seasons in the Interior especially for warm season flowers such as zinnias and celosia. Flower sizes and heights were some of the largest recorded. Local growers and homeowners grew spectacular gardens as long as they had access to irrigation. Annual and perennial landscapes and lawns showed severe water stress if they were not irrigated.


The last spring frost was 24 May (31°F, -0.6°C). Thaw degree-day accumulation was below the previous ten-year average of 3318.9 degree-days. The frost-free season was two days longer than the previous ten-year average. More than half of the summer precipitation occurred in July, but there were no adverse effects on vegetable growth. The weather statistics describe a fairly typical growing season for Fairbanks.

Most cultivars grew well, and harvest dates were typical for the Fairbanks area. Fall frost occurred on 13 September and did not influence the major harvest season for most vegetables. Temperatures dropped to 23.1°F (-5°C) on that date. Soils froze 1–2 inches and remained frozen for several days. Many local growers lost potatoes to freeze damage following vine removal because of the severity of the frost.

The University of Alaska Fairbanks Georgeson Botanical Garden, PO Box 757200, Fairbanks, Alaska 99775 (907) 474-5651,