Seasoned Flagstaff gardeners know the spring giddiness that overwhelms us on that first truly warm day in March is not the time to start planting. A common date that is often tossed around is June 15th as that is the last average frost date for our area.
Depending on where your garden is located within the greater Flagstaff area, gardeners can be spotted planting their veggies, annuals, and perennials anywhere from mid-May to mid-June. While a frost might not zap your freshly planted leaves into oblivion, there are other obstacles that make life in the garden difficult, and your plants will show it. This can be disheartening and disappointing as your garden vision does not meet your garden reality.
While June is a perfectly acceptable time to plant your garden, and for most vegetable crops that need ample time to grow and produce, it is an essential time to plant, the month of June at 7,000ft is harsh for plant life. This is the month that brings the highest midday temperatures of the year, often reaching 90 degrees. While this might not seem like much to those down in the valley, 90 degrees at 7,000 ft is a scorching heat. All one needs to do to learn this is sit in full sun without sunscreen for an hour (not recommended).
With this perspective, remember that those dahlias, tomatoes, and basil are not native to Flagstaff, thus they have no “sunscreen” plant adaptations, and their tender leaves suffer in the harsh full sun they require. On top of that intense daytime sun, the absence of the sun at night mixed with our thin high elevation air, leads to an exceptional temperature drop through the night.
At the Arboretum, we experience temperature swings of 60 degrees throughout June. Add the unforgiving arid winds of June into the mix, and those poor plants are out there having a hard time. One of the most common side effects I see in both native and non-native plants during this time is leaves turning a pale green color. This is known as chlorosis, which simply means a lack of chlorophyll in plant tissue. While there are a variety of reasons a plant can develop chlorosis from pests and fungus to nutrient deficiencies, environmental conditions like those previously mentioned can also have a serious impact on how your plants are photosynthesizing, leading to temporary chlorosis. Fortunately, these symptoms often go away once the clouds start rolling in and the monsoon rains start falling.
A Dahlia with Chlorosis
A much happier Dahlia protected from temperature swings and under shade cloth
Allium gooddingii protected from the harsh sun under shadecloth
For those plants that have been doing their best through this harsh month, there are a few things that can help them. Shade cloth during the mid-day sun can significantly help, as can adding a nitrogen rich fertilizer, such as fish fertilizer, into your watering program. For those gardeners who are looking to plant their plants and watch them thrive from the start, planting with the monsoons is the most ideal time. While it may seem “late” in the season, it is important to remember just how fast plants can grow once the temperature swings are less severe and the rains start providing the nutrients they need without human intervention.
The warmth, humidity and rain that come with our summer monsoon storms essentially eliminate those crazy temperature swings, lower the mid-day high temps and best of all, water the plants for you. Beyond providing water, those summer monsoons provide lightening which is a fertilizing agent. With every strike, the nitrogen in the atmosphere mixes with hydrogen or oxygen to create ammonium and nitrate, which are two forms of nitrogen. This nitrogen (which is the ‘N’ on that bag of fertilizer you have in your garage and that which was previously recommended to apply in June) melds into the atmospheric moisture and is washed to the earth in the form of rainfall. The plants then absorb that nitrogen and utilize it as a key constituent in chlorophyll (the green pigment of plants) hence healing them from the chlorosis induced by June extremes. So, if you’ve ever wondered why the plants look so lush after a monsoon storm, there you have it.
If you’ve ever wondered what the secret to a successful, effortless garden is in Flagstaff, you heard it here: plant with the monsoons! And if you must plant in June, it is best to nurture your plants with some temporary shade and a little nitrogen water to enable them to thrive.
Speaking of lush plants- we will have a ton at our Summer Plant Sale on July 12th! Lily of the Field, Warner’s Nursery and Wild Heart Farm will be selling their beautiful plants as well. It is a wonderful time to come out and support your local growers!
Gina Goegan is the Greenhouse Manager at The Arboretum
