Flagstaff High Altitude Organic Vegetable Gardening

Posted on April 25, 2010

My watering can with a recent dusting of snow.

My watering can with a recent dusting of snow.

I don’t think there is anyone in Flagstaff who actually enjoyed the wintery weather we had this past week, but take solace in remembering what locals know, “If you don’t like the weather in Flagstaff, wait a couple of days.” Despite spring’s fickleness, here in Flagstaff we know soon we will be enjoying some of the most beautiful weather Mother Nature offers up. And if you want to enjoy the spring and summer growing and harvesting your own veggies, there is lots to do…right now! But without the help of some local expertise, growing a garden here is downright frustrating. We have an abundance of rocks, wind, extreme dryness, pesky critters, cold nights, intense sun, and a short growing season to boot (about 90 days but varying to as little as 30 days in Baderville and as much as 150 days at the base of Mt. Elden).

This week I attended one of the best talks I’ve heard on the topic of organic vegetable gardening, presented by Jim Mast, Master Gardener, and sponsored by New Frontiers. Jim talked about four key principles (I’ve summarized them below plus added a few tidbits):

We have very poor soil all over Flagstaff. If you live in Lockett Ranches you are blessed with clay, in Doney Park you learn to love cinders. While the native plants are adapted to these conditions, if you want to grow vegetables, you must amend your soil with organic material. It is essential to balance the soil pH (7.0 or neutral is ideal — in Flagstaff we generally have 7.5-8.0 which is too alkaline and will limit nutrient availability to veggies). Amendments also attract earthworms and improve soil structure, critical for water retention and aeration. It is also very beneficial to add soil sulfur in the spring every year to balance your soil’s pH.

My compost pit -- the red wigglers are safe even in the cold temps!

My compost pit -- the red wigglers are safe even in the cold temps!

Compost is the best, and in my opinion, easiest way to amend soil. It’s a great way to make use of your deciduous leaves (if you are lucky enough to have them), pine needles, and kitchen scraps. I’ve had by far the most success with compost in Flagstaff by digging a three foot square pit about 18” deep (the pit prevents drying and speeds decomposition) and adding about one pound of red wiggler worms – nature’s rototillers. Rabbit manure is also really great because it is the gentlest manure as it doesn’t need to age to prevent burning your plants. If you purchase an amendment, look for one that has a balanced 10-10-10 analysis (Nitrogen, Phosphorous, and Potassium). All three are important to support vegetable plant leaves, fruits, and roots, respectively.

Ideally you should add a couple inches of amendment every year in the fall. But if you are just starting your garden this year, go ahead and add it to your soil now. Be sure to mix it thoroughly with your native soil. You will also want to clean your soil by removing and hauling off any plants that were diseased from the prior year, as well as (unfortunately) the soil that they were planted in. Healthy plants can be reworked back into the soil at the end of the season. Refrain from using synthetic fertilizers as they tend to be salt-based, which kills all of the soil’s living organisms and drives away earthworms!

While Flagstaff’s USDA zone overall is 5, there is considerably variation. The coldest areas are in Ft. Valley, getting colder the further out Highway 180 you travel. Parks, Bellemont, Kachina and Mountainaire are also cold areas. The warmest areas are in east Flagstaff. Jim explained that the base of Mt. Elden is actually called the “Elden Inversion Zone,” where the growing season is a full two months longer. If you want fruit trees that actually bear fruit, this is where to live! Another peculiarity is Doney Park, which tends to be warmer in the daytime but colder than areas of the city at night.

So why do we care about all of this? Vegetables are classified either as cool-season or warm-season. And you guessed it, the cool season crops are much easier to grow in Flagstaff. These crops are best planted early as they won’t be damaged by early frost, and they tolerate some shade (but keep in mind nothing likes to grow in full shade). Cool season crops include the leafy and root vegetables, such as spinach, lettuce, chard, beets, carrots, radishes, parsnips, peas, broccoli, cabbage, brussel sprouts, onions, garlic, shallots, and leeks. Not too bad of a selection in my view! To create or extend a cool microclimate, you can provide shade with fences, trellises, trees or large shrubs, and even other tall crops such as corn. Mulch cool season crops with organic mulches such as straw, needles or even blackprint newspaper (color print can be toxic). Wood chips are not the best choice as I’m told they tend to pull nitrogen from the soil for decomposition.

The warm season crops – melons, peppers, cucumbers, squashes, eggplant, and our beloved tomatoes – are more challenging here in Flagstaff. Jim suggested several techniques to create a warmer microclimate for these crops, including planting against south-facing or rock walls (malapais is great for heat retention). You can also use walls of water or one gallon milk jugs filled with water, which absorb heat in the daytime, placed around your veggies. Mulch with inorganic mulches, such as rocks, cinders, and gravel, to heat the soil. More expensive options include passive solar greenhouses and cold frames. I have seen some great passive solar greenhouses around town, and according to Jim, you can grow vegetables almost year-round with one, using a space heater when the temps are below zero.


Do you think we can grow this in Flagstaff?

Do you think we can grow this in Flagstaff?

Vegetables take varying lengths of time to mature from seed to harvest. Radishes are one of the funnest things to grow with children because it only takes about one month until you can enjoy them. My five-year old wants to grow watermelon this year, but they take three to four months – a definite gamble for a warm season crop with our short growing season! You should know not only how long things take to mature when planning your garden, but also time sowing with the conditions necessary for germination. Cool season veggies need to be planted early, from the beginning of April until mid-May (even if it snows!), while warm season crops should not be in the ground until rather late, from mid-May to June 1st.

The timing also varies between transplants and seeds sown directly in the ground. Root and leaf crops are typically shorter season and not good for transplanting. You can either buy or grow your own transplants. When a plant has two sets of true leaves, it is ready to transplanted outside. If you are purchasing yours, look for plants that are dark green, short and stocky with thick stems. Although perhaps counter-intuitive, avoid those that are already bearing fruit (think of tomatoes and peppers). If you get spring fever in February or March, consider growing your own transplants. The key is to have lots of light. Generally you will need 16 hours per day, with the light source (fluorescent) 1-2” away from plants at all times (this makes them short and stocky and not tall and spindly). South facing windows do not offer enough light. Be sure to acclimate transplants to the site where they will be planted to avoid transplant shock (hardening off). Set them out for a couple of hours each day, then a few more hours after a few days, and then leave them sitting out for 24 hours before actually planting them in the ground (this should take about five days total).

While there are thousands of varieties of seeds to choose from, for reasons already explained, in Flagstaff we should choose those that are short season and cold hardy. Jim recommends Pinetree Garden Seed for a great selection of short growing season seeds (they are out of Maine). Johnny’s Selected Seeds (also out of Maine) has the same planting calendar as ours. You can also check out local sources: Underwood Gardens in Chino Valley, Native Seed/SEARCH in Tucson, and Seeds Trust – my colleague Josh Robinson at Eden on Earth recommends this company for a lot of heirloom varieties.

There is so much great information for all of us determined, windswept gardeners here in northern Arizona — thanks to everyone who shares their tips and wisdom. Julie Lancaster has put together a great “Flagstaff Planting Guide.” It is a two-sided, laminated page loaded with information. What I like best about it is the Garden Timetable which tells you the best time to plant specific crops, based on information from Jim Mast, Viola’s Flower Garden, Sunset Western Garden Book, the Arizona Master Gardener Manual, and “lots of local lore.” You can find it all over town for under ten bucks at places like Warner’s, Viola’s, and even Ace Hardware.

Check back for more blog posts on organic vegetable gardening later in the season, and feel free to post with any of your own local lore! And don’t forget, if you have a specific question, you can submit it on my website’s E-Mail Q&A.

6 Responses to “Flagstaff High Altitude Organic Vegetable Gardening”

  1. Jim Vanell
    Apr 27, 2010

    Wonderful information. Thank you.

  2. Matthew Oldham
    May 02, 2010

    Thanks for the summary. I regretfully missed the workshop and was so happy to find the link to here.

  3. janel
    Nov 14, 2010

    Jim and Matthew,
    Glad you found it useful! How did your gardening go this season? I enjoyed homegrown tomatoes and pumpkins for the 1st time!

  4. Daryl and Meghan
    Apr 22, 2012

    Thanks so much for taking the time to post this. We are new to Flagstaff, having lived nearly twenty years in the Phoenix area, but having grown up in Eastern Washington with its similar climate. We are so excited to have a garden like we had there and this post has helped us immensely on our way.

  5. lorraine toscano
    Apr 29, 2012

    Thank you sharing. Im just starting–planning my raised garden. Feel a little out of my league-glad to find your site, will be back often!!!

  6. Jaimie
    Oct 15, 2015

    Considering gardening in Doney Park…so excited to know it’s a YES thing and we can do it. Moved here from Oregon where my garden was so bountiful. Excited to start working the soil!

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