Early Summer  

Planting.  By now, you’ve probably planted most of the cold-weather crops, and hopefully we haven’t had a frost to set them back.  If we have, try again with plants that won’t bolt (accelerated flower and seed production) in the mid-summer heat, such as lettuce, spinach, and parsley.  When evening temperatures begin to stay well above freezing, it’s time to plant the warm-weather crops, such as tomatoes and peppers.  Blankets and row covers can provide protection for the more tender plants on cold nights to prevent sluggish growth.  You can also start planting summer blooming annuals and perennials.  As bulb leaves die back, you can dig the bulbs and amend the soil with organic materials before replanting in the same spot or moving to a new location.

Fertilizing.  Fertilize lawns, flower beds, and vegetables after thinning to give them a good start for the growing season.  Organic based fertilizers are available for lawns, as well as your other plants.

Watering.  We’re heading into the warm and dry season.  If you want good growth and flowering during this dry part of the summer before monsoons, water regularly and deeply, typically once each week under normal conditions, but more frequently when it gets above 90 degrees.  Many established native plants will get by with less frequent watering until the monsoons, when they will put on their show.  Be sure to check your irrigation systems periodically.

Mulch.  If you previously removed all mulch to warm the soil, you might want to redress the soil around your plants with a thin to moderate layer to reduce water evaporation and to control weeds.

Pruning.  Once early blooming shrubs have completed their flowering, it’s time for their annual pruning.  Spent spring flowers should be removed at this time so the plant will focus their energy on this year’s growth.  If your fruit trees have by good fortune produced an overabundance of fruit, begin thinning fruits to several per branch to get larger fruit.

Mid-Summer

Planting.  If you are a bit of a risk-taker (which includes anyone growing veggies around Flagstaff, right?), calculate backwards from the expected date of the first hard frost for your location to determine when to plant a second round of quick-growing vegetables that can take the cool early fall nights (kale, spinach, onions, radishes). 

Fertilizing.  Feed annuals, potted plants, and vegetables monthly through the growing season. 

Watering.  Continue to deep-water lawns, perennials, shrubs, and trees until the monsoons arrive.  Keeping lawns 2 to 3 inches in height will help protect against drying out by keeping the ground shaded and therefore cooler.

Maintenance.  Try to keep up with the weeds before they go to seed to minimize future weeding efforts.  For those weeds with stout roots that are difficult to pull out completely, keep removing the top growth every two weeks to drain the energy out of the roots.  Be persistent, and you’ll eventually win the war through attrition!

Late Summer

Planting.  Monsoon season is a great time to plant perennials, shrubs, and trees for next year.  The higher humidity and frequent, if not regular, precipitation greatly reduces the stress of new plants getting started and gives them time to establish new roots in the soil before the onset of winter.

Watering.  Hopefully, the monsoons have arrived in earnest and you can cut back or eliminate regular watering of your gardens.  Remember to check irrigation timer clocks to be sure lightning storms haven’t disrupted the clock or any of the programming.  Now is a good time to replace the batteries since fresh batteries will be more likely to maintain your programming even with a few electrical disruptions.

Harvest Time!  Hopefully, you are harvesting lots of wonderful goodies from your vegetable gardens by now.  If cold nights are predicted, cover the warm-weather crops at night.  Keep picking your produce in its early stages for the best flavors and textures and to keep the plants producing.

Planning Ahead.  It’s also time to order bulbs for fall planting.  At this elevation though, spring may be a better time to plant bulbs so that they are not battling the intense cold of our winters before becoming well established.

Winter Gardening  back to top

Winter temperatures fluctuate dramatically at high elevations in northern Arizona. During the winter months, the thermometer often varies daily by 30 or more degrees. Daytime temperatures are often in the 40’s and 50’s, while nighttime typically drops well below freezing.

During the winter, the surface cells in plants warm up in above-freezing daytime temperatures. Then night-time chills plunging significantly below 32 degrees may freeze young tissues. Young tissue is especially prone to damage from alternating freezing and thawing. Sunscald may occur in late winter or early spring when the temperature of bark in direct sunlight may be higher than the surrounding air. After sunset, plummeting temperatures may quickly refreeze the water in the cells, splitting the bark and causing large wounds. During extended periods of intense cold, frost can penetrate into bark and deeper wood cells.  Repeated freezing and thawing of the soil can cause heaving of soil and plant roots. This exposes roots to desiccation and freezing. Once the soil and roots are frozen, the roots can no longer take up more water for the rest of the plant.

Winds. Wind can cause several problems for plants. It can damage young tissue due to its cooling and drying effects. In spring, as the days grow longer and the air begins to warm, plants are induced into higher rates of transpiration, increasing the rate of moisture loss.  However, cool winds and deep mulch may keep the soil from thawing, and the still-frozen roots are unable to replace the moisture lost from the aboveground parts of the plant. The top or all of the shrub or tree may die back, and it may take most of the next growing season for the plant to recover from this “windburn” damage.

Winter Garden Maintenance
So what can you do to minimize some of these winter stresses to your plants?

Mulching. Once the soil has frozen in early winter, mulch around the base of shrubs and trees with an organic material to a depth of 6 to 8 inches. The insulating effect of the mulch will help prevent heaving and keep the plants in a state of dormancy during occasional periods of warmer weather. Snow itself acts as an excellent insulator if it remains for long periods. For groundcover plants, use a material that will allow air circulation and will not mat down. This prevents low-growing perennials from rotting underneath the mulch. Pine needles, wood shavings, and dry oak leaves work well for this purpose. Remember to remove mulches early in the spring to allow the soil to thaw before bud break so that the roots can once again take up water.

Pruning. Snow can present problems, particularly structural damage to shrubs and trees. Large branches with a lot of surface area are the most susceptible to breakage from heavy snow or ice. Inspect your plants for the need for preventive pruning and complete that pruning early in the winter season if possible. Otherwise, try to remove buildup of snow from branches or plants that may break under too heavy a load. If any branches should break, prune off the damaged material as soon as possible to minimize additional stress to the plant.
For other pruning, it is best to wait until late February or March, but before bud break. Pruning before or during the coldest part of the winter may increase the stress to the plant from greater desiccation at the cuts. Pruning in the fall before complete dormancy may stimulate new growth, which would be highly susceptible to freezing and desiccation.

Wind protection. Setting up wind blocks can protect smaller shrubs and trees vulnerable to damage from wind and cold. Techniques include wrapping with burlap, placing cardboard or other stiff material around the plant, and setting up straw bales on the windward side of the plant.

Watering. One other factor to keep in mind throughout the winter is the moisture content of the soil. Even though dormant, plants continue to transpire through the winter, though at a lower rate. If little precipitation occurs, drought stress can kill plants as readily in winter as in summer. At the minimum, your trees and shrubs should receive water about once a month. If there is no snow or rain (and if there is a point when the ground is not frozen) try to give your plants a good soak well into the root zone every month or so during the winter.