Millions more people became gardeners for the first time in 2019, according to Monrovia, one of our nation’s top plant growers in the USA. At least 80% of these new gardeners are millennials The new gardening boom, coming from all generations, may becoming more popular due to serving as relief from a stressful world and reaction to the abundance & availability of new plant species as well as new varieties developed from old favorites that are more compatible for our compact urban gardens and landscapes.

For new and seasoned Treasure Valley gardeners, along with our rapidly growing population moving from all areas of the country, basic understanding of lawn care in Boise is needed.

• What is the Treasure Valley Hardiness Zone?

Our USDA hardiness zone is officially zone 7, however, we are safer to assume our hardiness zone to be zone 6. We have experienced zone 6 winters the past two to three years since the USDA raised our zone to 7. Zone 7 means expected winter low temperature does not drop below 0 degrees F. However, our Idaho temperatures have dropped below zero the past few years. When you are looking to buy plant material, watch for the hardiness indication on the plant labels.

When considering lawn care in Boise, it’s important to know that our last average frost date is May 10th. If you have frost tender plants to transplant in the spring, it is probably safer to wait until June 1st. Our average first frost date is October 10th. Therefore, the Treasure Valley has a 5-month growing season. Keep in mind that frosts may be earlier or later than average. Generally, here in the Treasure Valley, winter is over when the last snow on Shafer Butte has melted. Everyone can see this from the Valley.

Another aspect new gardeners should be aware of is watching for the spring bloom of bright yellow flowers of the Forsythia. Once these shrubs have bloomed, you can safely prune roses and/or apply crabgrass preventative to your lawn. Crabgrass germination requires as many chilling hours as the Forsythia needs to bloom,

Check out the Farmer’s Almanac Planting Guide link below: https://www.almanac.com/gardening/planting-calendar/zipcode/83646#

• What is the Treasure Valley Climate?

Our Idaho climate is a steppe climate. According to the National Geographic Society, a steppe is a dry grassy plain. Steppes occur in temperate climates, which lie between the tropics and polar regions. Temperate regions have distinct seasonal temperature changes, with cold winters and warm summers. Steppes are semi-arid, meaning they receive 10-20 inches (25-50 centimeters) of rain each year.

Here in the Treasure Valley, our average annual rainfall is 12 inches with low humidity. In respect to gardening, some residents receive water from irrigation canals throughout the Valley. The rest of our residents must rely on irrigation from private wells and/or city water. City water is expensive, so drip or soaker irrigation is recommended. By utilizing “point source irrigation methods” to your desired plant material, you will reap the benefits of optimal plant growth and production. When applying the water directly where needed instead of overhead watering, germination of weeds is reduced.

Most garden plants require an inch of water per week. When daily temperatures rise over 100 degrees F. plants will require more watering. Between June through September, we normally only see 1-2 days of rainfall.

Those who conduct lawn care in Boise understand that our arid climate makes weather comfortable and protects our plants from many diseases. We seldom have wet springs that could develop bacteria and/or fungus on trees, plants and lawns.

• What is the pH of the soil in the Treasure Valley?

Let’s look at how this is measured and why pH is important. The definition of the pH Scale, from Business Directory.com is as follows:

A measure of acidity or alkalinity to water soluble substances (pH stands for ‘potential of Hydrogen’). A pH value is a number from 1 to 14, with 7 as the middle (neutral) point. Values below 7 indicate acidity which increases as the number decreases, 1 being the most acidic. Values above 7 indicate alkalinity which increases as the number increases, 14 being the most alkaline. This scale, however, is not a linear scale like an inch or centimeter scale (in which two adjacent values increase or decrease by a factor of 10. For example, a pH of 3 is 10 times more acidic than a pH of 4. Similarly, a pH of 9 is 10 times more alkaline than a pH of 8, and 100 times more alkaline than a pH of 7. The pH scale was invented in 1909 by the Danish biochemist S.P. Sorensen (1869-1939).

Our Treasure Valley soils are typically highly alkaline with high percent of calcium, particularly south of I-84. Existing plant compatible soils are primarily the result of proper farming practices done over the years. In the Treasure Valley, we have a hardpan in our soils at various depths, especially south of the Boise River. This hardpan is called ‘caleche’, and is equivalent to a 2-inch thick layer of concrete. In some southern areas of the Treasure Valley, caleche is 30 inches below surface, but properties further west find it’s closer to the surface. If you’re growing tap rooted trees, break up the caliche before planting.

With care, you can grow acid-loving plants here. Some gardeners plant blueberries in pure peat moss, for instance. Azaleas and rhododendrons must be fertilized with acidic fertilizer.. If you are set on growing bog plants, buy a child’s wading pool, dig a hole so that the pool can be set into it to its brim, then poke holes for drainage and fill the pool with soil, peat moss and water (watching out for the pH in the mix of soil and peat moss).

Enjoy fellow lovers of the landscape! Keep the unique environmental conditions in mind while discovering how wonderful and fruitful gardening can be in the Treasure Valley!

Cindy Boian

Diamond Lawns

“I have been in the landscape and nursery field for forty years in some related capacity. I have earned a Landscape Horticulture Degree from Colorado State University. Previous to CSU, I attended Larimer County Vo-Tech in Fort Collins, Colorado where I graduated from their yearlong horticulture program. My experience has spanned from nursery development and production to owning my own landscaping business, working as a florist to landscape maintenance and design. My expertise and love of the high plains and mountain plant material has been a passion of mine. Through my current position of Operations & Sales Manager at Diamond Lawns, I am so fortunate to educate and help to create beautiful sanctuaries for clients.”