Thinning vegetable seedlings

Thinning overcrowded seedlings is essential following germination. Seedling competition will set back your crop and delay harvest. Some people prefer to thin partially as a hedge against possible later seedling losses. Whether you thin partially or completely to final spacing, do thin. The following photo log provides tips and tells you how. Note that these photos picture thinning for a wide bed or Block style layout, not a row. Wide bed planting results in a greater harvest for your efforts.

New vegetable garden soils

So you've dug up soil for a new vegetable garden and are less than pleased. Heavy clays, low organic matter content and mixed top and subsoil layers are typical of urban Front Range soils around homes. What are your options?

Just like a human baby can’t do everything that an adult can do, a new garden soil can’t be expected to grow what a long-time garden with carefully cared for soil can. And don’t think that tossing a handful of fertilizer on these tough-to-garden soils will solve your problems. Poor physical soil conditions are the issue, not fertility.

Foot-long ‘Imperator’ carrots are likely not in your immediate future. Perhaps golf ball like ‘Thumbelina’ carrots are a more achievable objective. Better yet, rather than thinking about carrots that require loose soils for root development, consider fibrous rooted, pioneering crops such as lettuce, spinach and kale.

Another thought is to work on soil building your first year. Apply 2 inches of organic compost in the spring and mix in to the top 4 to 6 inches of soil. Plant a summer cover crop such as buckwheat (photo right), till it under in the fall and immediately plant a winter cover crop such as winter (annual) ryegrass. Let the roots of these crops do the work of penetrating these tough soils. Through their burial, add fresh organic matter to feed beneficial soil microbes and build your soil. Ideas on cover crops for Colorado conditions can be found in the CSU Garden Note #244, Cover Crops and Green Manure Crops.

Raised beds with hard sides (wood) or soft sides (soil beds photo left) are another option. Moving or importing desirable soil to construct these beds increases the depth of useable soil and jump-starts your efforts at building a good garden soil. Note that they too will likely require soil building measures such as compost additions and planting cover crops.

A final thought is to avoid overtilling your soil. Beating it up with a tiller is not the answer to building a good soil. Have a good reason to till (turning under a cover crop or mixing in compost for example) and don’t till frequently. Also till at moderate moisture content – not too dry and not too wet. Care for your garden soil and it will care for you.

How do you manage your garden soil? Comments welcome.

Pear Picks

Pears are a good fruit choice for the Front Range. They bloom late, usually just before apples. Pears are subject to fireblight disease like apples so look for fireblight resistance. Fruit is borne on two year old or older spurs (short, stout twigs) also like spur-type apples.

In choosing a tree for planting, remember that pears are self-fruitful but bear better when planted with a second pollinator tree. Magness is a variety often used for pollination and it shows good fireblight resistance. Any variety that blooms at the same time will serve as a cross-pollinizer.

Both European pears, Asian pears and their hybrids can be grown. Note that Asiatic pears have a lower chilling requirement than European types. Asian pears generally are also less resistant to fireblight.

European pear suggestions include Bartlett (an early summer pear, left in photo) , d’Anjou (right in photo), Bosc and Lucious. Hybrid pears grown here include Maxine (good fireblight resistance) and Kieffer. Of the Asian types, Shinko shows more fireblight resistance.

As in previous fruit tree adaptation discussions [see “Fruit trees on the Front range” March 12], be forewarned that our erratic climate makes this a difficult fruit growing location and these are only suggestions, not recommendations. Comments on your pear growing successes and failures are welcome.

[Pears in basket photo credit, Carl Wilson]

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]