Regional Gardening Reports :: National Gardening Association

In the Garden:
Southwestern Deserts
October, 2006
Regional Report

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Kale is a nutritious veggie that also adds color and texture to the winter garden.

Planting Cool-Season Vegetable Beds

Fall weather signals the much anticipated arrival of the major planting time for low-desert gardeners. We enjoy two distinct planting seasons for annual vegetables, with different veggies thriving in each season. The trick is knowing when to plant what! If you can eat the roots (beets) or leaves (spinach), or if it is a member of the cabbage family (also called cole crops), it is a cool-season veggie. Peas don't fit in those categories but they are also grown in cool weather. (We eat the fruits of warm-season veggies, such as tomatoes and peppers.) Sow seeds or set out transplants for leafy and cole crops. Root crops are best sown directly in place.

Roots: beets, carrots, kohlrabi, leeks, onions, parsnips, radishes, rutabagas, turnips.

Leaves: celery, chard, collards, endive, leaf lettuce, mustard, spinach.

Cole crops: bok choy, broccoli, brussels sprouts, cabbage, cauliflower, Chinese cabbage, kale.

Prepare Garden Beds
Before planting, it's essential to improve garden beds. Landscape plants don't need soil amendments, but non-native annual veggies need rich, organic soil to accomplish their goal. They have a relatively short time frame to germinate, establish roots, send up leaves, mature, flower, and set seed before they die. Start by loosening soil to a depth of 12 to 18 inches. If that isn't a viable option because of hard or rocky soil, build raised beds to at least that depth. (Consider waist-high beds if kneeling or mobility is an issue. It's kind of fun to stand while gardening, especially as knees become creaky!)

Layer 4 to 6 inches of compost or well-aged manure on top of the soil. There's nothing like rotting organic matter for growing a healthy garden! Organic matter improves drainage in clay soil, enhances moisture retention in sandy soil, and adds nutrients to any soil type. Organic matter enhances the "feel" of soil and invites earthworms to the party, which do a terrific job aerating with their tunnels and adding nutrients in the form of castings, or droppings.

Adding organic matter isn't a one-time project. It's essential to incorporate another 4 to 6 inches before each planting season. That means if you grow a warm-season garden, compost is added twice annually. Within a few years your garden will feature rich, dark soil that is easy to dig with a trowel. I promise!

Next, add nitrogen and phosphorus fertilizers according to package instructions. Our desert soils contain sufficient potassium so it isn't necessary to purchase fertilizer that contains it. However, it does no harm to include it if it's already contained in the product sitting on your shelf. Fertilizer packages are labeled with three numbers, called the NPK ratio. This refers to the percentage of N (nitrogen), P (phosphorus), and K (potassium) in the bag. There are different formulations for different purposes. In general terms, nitrogen encourages lush green growth, phosphorus strengthens stems and promotes flowering, and potassium keeps the root system healthy.

Nitrogen is able to move through the soil, penetrating deeply enough for roots to absorb. Phosphorus, on the other hand, does not move readily through the soil, so if sprinkled on top of a bed, it doesn't do much good. It needs to be dug in and incorporated throughout the soil, or placed near the root zone during planting, where roots will grow into it.

Ammonium phosphate (16-20-0) is a relatively fast-acting chemical fertilizer. Organic nitrogen sources need to break down further before they are available for roots to uptake, but over time, they help build a healthier soil. Sources include alfalfa meal, blood meal, coffee grounds, cottonseed meal, fish emulsion, and bat or seabird guano. Organic phosphorus sources include bone meal and rock phosphate.

As a final addition, add soil sulfur or gypsum according to package instructions. They both improve drainage. Soil sulfur also slightly reduces pH, which is helpful for veggies that originated in acidic soils. However, the effect is very temporary and local. It isn't possible to permanently or greatly influence our high pH (alkaline) soil characteristics.

Turn all the amendments into the soil, mixing thoroughly. Rake smooth and you're ready to grow delicious cool-season veggies!

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