A Tale of Peaches and Potatoes

by guest writer Robert Cox, Colorado State University Extension Horticulturist, Arapahoe County

Gardeners may wonder why they cannot order certain peach trees from out-of-state nurseries. The catalog description may say that the peach variety “cannot be shipped to Colorado”.

There are two quarantines on peach tree shipments in the state. One prevents the shipment of white-fleshed or clingstone peach and nectarine trees into Mesa County, Colorado. This is meant to exclude peach mosaic virus disease from Palisade area orchards.

The other quarantine prevents the shipment of peach and related Prunus (cherry and plum) trees into the San Luis Valley. Peaches can be the winter hosts for green peach aphid that carries potato viruses. When peach aphids move to potato plants in the summer, the crop can become severely diseased and decimate yields.

Some out-of-state mail-order nurseries do not attempt to determine county of residence when a Front Range Colorado customer submits an order for a quarantined peach tree. The nursery may instead choose not to send a quarantined tree to any address in Colorado. While frustrating, little can be done but look for another supplier willing to recognize that your address is not in the quarantine area.

If it’s a small consolation, many states have similar quarantines on plants that could introduce diseases or insects to an economically important crop. Both peaches and potatoes are Colorado agricultural success stories and worth millions of dollars in income to the state.

[Peach photo credit, Carl Wilson]

Kewl Kale

I get excited about kale because it is by far my favorite cooked green. When steamed, it retains more texture than spinach. It can also be chopped raw and used in salads. Kale is a good source of vitamin A and calcium. Mostly, I just like the taste, appearance in the garden and ease of growing.

Grow kale as a cool season vegetable in spring and again for fall, filling in with a warm season succession crop in summer. I planted mine before the end-of-March for seed to reap moisture from Front Range spring snowfalls. Do plant by mid April to squeeze in a crop before weather potentially turns hot in June. Quality decreases in hot weather and leaves can turn stringy. Turn to growing more heat-tolerant collards for summer cabbage family greens.

Kale is a tough, pioneer crop for gardeners planting new ground. The round, pellet-shaped seeds are planted only ¼ inch deep (seedlings photo left). Although not as small as lettuce seed, I cover with seed germination fabric to combat soil drying from strong spring winds and intense Colorado sun (see March 6 post, "Seed germination in Dry Climates").

Plants mature in approximately 2 months but leaves can be harvested at any stage of development. Pluck leaves from the outside, allowing plants to push new leaf replacements from the interior to extend the harvest. The new interior leaves are tender and best for salads. Kale stores exceptionally well in the refrigerator.

This year, my spring crop variety is ‘Lacinato’, also known as ‘Toscano’ or dinosaur kale due to the variety’s dark, puckered leaves (left seed packet above). ‘Red Winter’ also known as ‘Red Russian’ is a rugged-looking heirloom variety good eaten raw in salads (right seed packet above). The most widely grown variety in the U.S. is ‘Vates Dwarf Blue Curled’, a ruffled leaf variety developed in Virginia in 1950 (center seed packet above). For an ornamental but edible touch, plant the red-purple leafed ‘Redbor F1’. Keep in mind that the red color develops better in cool, fall weather than in summer heat so planting mid-summer for a fall crop should be considered.

Kale is relatively pest free but occasionally can develop cabbage aphids.

[Kale seed packets and seedling photo credit, Carl Wilson]

Apple choices

As discussed two posts ago, choosing fruit varieties for the Front Range is tough. Finding a variety that will emerge from dormancy at the right time after a warm-cold-warm-cold “roller coaster” winter, bloom at the right time to escape erratic spring frosts, and then mature fruit in our short growing season is challenging.

Apple choices also should be fire blight and to a lesser extent powdery mildew resistant. Most of the variety suggestions from knowledgeable people are not ones you see in grocery stores. They also may be challenging to locate.

Dr. Harold Larsen, CSU fruit researcher on the West Slope, suggests disease resistant cultivars Freedom, Jonafree, Liberty, Prima, Redfree, Pristine (summer apple), Goldrush and Enterprise (highly fire blight resistant) on M-26 or EMLA-26 rootstock. Consider Empire and Williams Pride on M-7A or EMLA-7A rootstock.

Scott Skogerboe, Fort Collins nurseryman, suggests Honeycrisp, Cortland, Harleson, Redstone Canyon Gold, Zestar, State Fair, Joyce and Duchess of Oldenburg.

Carol O’Meara, CSU Extension Agent in Boulder, lists Connell Red, Haralson, Honeygold, Keepsake, Prairie Spy, Regent, State Fair and Sweet Sixteen.

Apples usually need a pollinator although crabapples blooming at the same time can pollinate apples. Keep in mind that these suggestions are for an area with a climate that is less than desirable for growing fruit trees so moderate your expectations accordingly.

[Apple photo credit Carl Wilson]

Peas please

Peas are a snap when you plant early. In fact, research shows you can enjoy a 50 percent higher yield by planting April 1 or earlier than if you delay until May 1. The name of the game really is to sneak peas in during cool spring weather before Front Range summer heat arrives. We don’t tend to have too much mild temperature weather in-between to keep vines going.

You are cleared for planting anytime after soil temperatures have warmed to at least 40 degrees at a four inch depth. Choose a variety from one or more of the three main types of peas.

• Snow peas have small, underdeveloped peas in tender pods and are used extensively in Chinese cooking.
• Snap peas produce edible pods or you can allow pea seeds to partially mature before harvest.
• Shelling or garden peas contain tender sweet peas nestled in tough, inedible pods. Early and mid-season varieties may do better here than late types due to our hot summers.
  

Well-drained soils are necessary for good pea growth so prepare soil well before planting. Fertilizers are generally unnecessary unless you garden in a nutrient-poor sandy soil. Soak seeds in water overnight to speed germination. Dust before covering if using optional nitrogen inoculant. This inoculant, which is available at most garden centers, is the companion bacteria that enable pea roots to absorb nitrogen directly from the air. It may be useful the first time you plant peas in your soil. Cover with one inch of soil and water seeds to firm the soil around them.

Young peas are vigorous growers and will require about a half inch of water a week until bloom time and one inch a week until pods fill out. Water carefully, especially with clay-type soils. The soil should never become waterlogged, a condition that promotes seed rot. Too much water before flowering will usually reduce yields.

Dense plantings both increase your harvest and enable the plants to support themselves. This is especially true of the bush or dwarf types like 'Petite Pois'. Because of our winds, varieties that reach 18 inches or more will require some type of support.

Netting the height of the pea variety stapled to wood posts is easy. Some folks use a frame with twine anchored in the ground with a nail. Others use cut wood brush for a rustic but quickly obtained support.

Late snows and frosts are not a problem for these tough plants. Tough, that is, until summer heat takes down the plants of gardeners making late plantings. You can add more soil or mulch such as dried grass clippings on top of the soil when plants reach 6 inches tall. This helps to keep the roots cooler as the season warms.

When harvesting, pick only the peas you can eat that day. They don’t keep well and begin losing their sweetness the moment they’re harvested. Just-picked freshness can't be bought at any supermarket.

Harvest snow peas when the pods are tender and supple and before the peas mature. Snap peas are ready when the pods are still crisp. Shelling peas are ready to pick and shell before the pods harden and fade in color.

When peas are finished, you are ready to plant another vegetable crop (“succession planting”). Pea roots enrich the soil for later crops and the vines make excellent compost.

Insect problems generally are few with two exceptions. Pea aphid (left) is common and can be controlled with a good dousing of water to knock them off or insecticidal soap sprays. More problematic is thrips (right, magnified) that cause a silver scarring on leaves and pods. Control with washing plants, insecticidal soap sprays, and yellow or light blue sticky traps.

With planting early you should be enjoying peas at their prime by late May to early June

[Both peas photos credit Carl Wilson] [Pea aphid phto credit, Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org] [Thrips photo credit, Jack T. Reed, Mississippi State University, Bugwood.org]

Fruit trees on the Front Range

The biggest challenge with growing fruit trees on the Front Range is winter and spring “roller-coaster” temperatures. Fruit trees must tick off chill units to complete winter rest. Each variety has unique number of chill units. Warm temperatures above 55 degrees F will subtract from accumulated chill units delaying spring growth. Sound like this past winter? Once the rest requirement is satisfied, chill units are ignored until fall when they are reset by the next winter dormancy.

Following rest satisfaction, plants begin accumulating heat units for growth until full bloom. Again, each variety has a unique number of heat units (called growing degree hours or days). If this number of heat units is small and the tree is in full bloom when temperatures drop, blossoms freeze and the fruit crop is lost.

Finding fruit trees “programmed” with the right chill units and heat units for the Front Range is hard due to the unpredictability of our winter and spring temperatures (the “roller coaster”). While some trees may fruit one year, the crop is lost the next. With many types of fruit, realizing a crop one or two years out of five is typical. This is why there is no substantial commercial fruit industry here and instead it is found on the West Slope where temperatures are moderated.

What are the most reliable fruit tree varieties for the Front Range? Of course some that will grow here have other problems such as how susceptible apple and pear varieties are to fireblight disease. This is the time for readers to step up and tell us their experience. What type of tree fruit do you grow (apple, peach, cherry, plum etc.), what is the variety, what is your crop record (estimated number of crops in the last 5 years), and tell us your Front Range city?

Click comment below and let us know.

[Bowl of apples photo credit Carl Wilson]

Seed germination in dry climates

Mid-March is generally the expected seeding date for cool season vegetables along the Front Range. These include lettuce, onions, peas, radishes, spinach and cabbage. Earlier sowing may be possible this year because soil temperatures already have warmed to 40 degrees F (check Fort Collins soil temperature website mentioned last post). Of course soil temperature can drop lower with extended cold and cloudy weather.

Small seeded vegetables such as lettuce can be a challenge to germinate in dry climates. If small seed is planted deep so it doesn't dry out, it won't germinate. Planting shallow and just barely covering with soil raises the danger of drying out which kills germinating seeds. The following technique can help you overcome the challenge of our low relative humidity and winds that dry the soil surface.