Steamboat Springs A couple years ago, an acquaintance of mine purchased giant pumpkin seeds as soon as they became available in March. To offset our short growing season, he started the seeds indoors and then set the seedlings outside once the danger of frost had passed. Rick had high hopes for a field of the orange gourds by the time Halloween rolled around. Alas, it didn't happen.
Can we grow pumpkins here in the mountains?
The short answer is yes. But it takes a little extra work.
Pumpkins, along with cucumbers, squash, muskmelons and watermelons, are warm-weather plants that grow best at elevations below 5,000 feet. They need a long growing season with warm and sunny days. Pumpkins require a growing season of 90 to 120 days, depending upon the variety of seed being grown. (Autumn Gold, a hybrid variety, takes 90 days, while Big Max, which can grow to 200 pounds, takes 120 days.)
However, you can extend our short growing season by starting seeds indoors. When it is time to plant them outdoors (about a week after the average last frost date of June 11), care must be taken not to disturb the roots of the seedlings. This is one plant that does not like its roots disturbed. Use a thermometer to make sure the soil at the 2-inch depth is 60 degrees Fahrenheit before planting the seedlings outdoors. A location close to the house will help keep the plant warm with reflective heat.
Pumpkin seedlings should be planted about 4 feet apart in mounds of soil that have been fertilized with nitrogen, phosphorus and potash as well as organic matter such as compost or aged manure. A soil test will help you determine which nutrients are needed and how much to use.
As the seedlings grow, more and more water - as much as 1 1/2 inches per week - will be needed. As the plants mature, flowers will appear; usually male flowers appear before female flowers and then insect or hand pollination will need to take place for fruits to be formed.
To help the plants obtain the most water and nutrients, it is recommended that the pumpkins be culled to one per plant once they reach about 10 inches in diameter.
Pumpkins can be harvested once the skin hardens and the color deepens to a uniform orange hue. Pumpkins have a tendency to harden prematurely when left out in direct sun, so you might want to construct a shade out of burlap or other lightweight material toward the end of the growing cycle.
You'll also want to protect the fruit from a hard frost at the iffy fall time of year since that will cause the pumpkin to soften and rot.
There are many local gardeners who experience success with pumpkins here. Go ahead and give it a try next season for a colorful fall garden display.
Deb Babcock is a Master Gardener through the Colorado State University Cooperative Extension Office in Routt County. Questions? Call 879-0825 or e-mail firstname.lastname@example.org.