Transition to September Planting Season

08/29/2019 | Ken Davis Fall, Garden Tips, In the Garden

By Ken Lain, the mountain gardener

Many of us have gardened in places where the soil is rich, its pH perfectly balanced, the climate blessed with consistent rainfall, gentle sun, and plant-coddling humidity.    Mountain soil and climate present the opposites of such ideal gardening conditions!

Here’s an encapsulated definition of the characteristics of mountain gardening and how to contend with them: 

The local USDA garden zone is 6b with a definite influence from zone 7.  This defines our area as mild, but with a definite winter and possible subzero temperatures.

Never, but never, underestimate the Arizona sun, wind, and dry air.  They are major influences in determining which plants do well in our landscapes, and which ones won’t.  Local soils are typically heavy clay with very little organic material.  Therefore, soil preparation for planting is of extreme importance. It demands the addition of composted Premium Mulch to your soil to either hold in the moisture for granite soils, or to prevent clay soils from compacting.  Our soil is alkaline and usually doesn’t need the addition of either lime or wood ashes, which would increase its already high pH.

When selecting plants for mountain landscapes look for those with thick, leathery leaves; they allow plants to retain a high degree of moisture and to be less prone to tearing in the area’s fierce windstorms. This is where it pays to talk to a gardening expert with some experience in local landscapes.  It can save you a whole lot of time, energy, and expense in creating your landscape.

Mild winter temperatures provide enough of the chilling necessary for all the deciduous fruits and perennials to thrive in the region.  They include apples, peaches, cherries, grapes, and berries. Get a free copy of my new Fruit Tree Book for more informative help. This climate also is conducive to blooming deciduous shrubs such as lilac, forsythia, hardy camellia, rose of Sharon, butterfly bush, and Russian sage.  Some of the loveliest roses in the country thrive here without the tedious demands of constant tending necessary in more humid climates.  Thanks to the low humidity and mild winters, mountain roses experience few problems with bugs, mildew, and virtually no black spot.

The climate is so mild that we garden and design landscapes 12 months of the year.  The average last frost date in spring is Mother’s Day.   However, spring is so mild that our cool-season gardens can be planted as early as March 1st.  These can include lettuces, spinach, broccoli, potatoes, onions, radishes, and more.

The first light frost happens on or about Halloween, depending on your garden’s specific elevation, but all mountain gardens look great through Thanksgiving.  This makes the average frost-free growing season in our region approximately 150 days long.


The area is surrounded by National Forest lands so plant-eating mammals can be threats to all gardening efforts.  Javelinas, deer, antelope, rabbits, squirrels, and gophers all have the potential to devour portions of a carefully planned landscape.  It is essential to be very selective of the plants used for landscaping in these critter-populated areas.  This is another case where professional advice can save you many headaches and costly errors. The next time you visit Watters ask for the printed handouts that tell which plants mountain critters won’t eat. 

Labor Day is the official start time of fall planting in the region, so that means there are two months left to our warm-weather growing season. If you’ve been considering a landscape addition to create more seasonal excitement in the garden, now is the time to take action. Whether planting some of the past season’s stock or new arrivals, the plants have plenty of time to develop extensive root systems before winter. Garden success definitely increases when plants are put in during the monsoon season. Many that bloom in late summer and autumn are especially happy when planted this time of year.

Truckloads of winter evergreens and trees ready for fall color are on their way. The first of many deliveries arrive this week!  To prepare for this seasonal transition Watters hosts its annual clearance sale, aka the ‘Monster Monsoon Sale.’  There is nothing wrong with these lower-priced plants, but the spring and summer stock simply must go to make room for the fall and winter selections.  I even have been known to give away free plants when I know they’re going to a good home!

The sale encompasses a couple of weekends, so the best savings of the year are to be had within the next few weeks.  Get in to scoop up the deals as early as possible, because savvy gardeners know to take advantage of these between-season sales. The limited quantities go fast!

Except for mums and asters, the garden center DOES NOT want any leftover perennials during its transition into the autumn planting season. So, if the plant you want isn’t on sale, ask for a discount. We are remarkably receptive to giving you “a deal,” especially when you offer to take home more than one plant. 🙂

Until next week, I’ll be helping “transitioning” local gardeners here at Watters Garden Center.
Ken Lain can be found throughout the week at Watters Garden Center, 1815 W. Iron Springs Rd in Prescott, or contacted through his web site at or .

4 Replies to “Transition to September Planting Season”

  1. Thank you I am new to the area and this was very informative. Angela Reynolds

    1. Glad it helped. We will be having a Gardening for Newcomers class on Saturday October 5th that you might find helpful.

  2. Thank you for all the great articles and wonderful advice!! I’ve been an avid gardener for many years .. however, I still have much to learn. Gardening in PV is very different than in San Diego. The one major advice you gave was using Nolo for dealing with the grasshoppers from HELL!! Made a big difference in this years veggie garden! ?

    1. Gald we are able to be helpful. If you are not already aware, we run a garden class each Saturday. If you are unable to attend in person we also Livestream on Facebook and post an edited version on YouTube later in the week.

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