Rye cover crop thoughts

Winter rye also called cereal rye is growing well in these warm days of spring. There are advantages to turning under now while it's still succulent. There is less nitrogen tie-up than waiting until later when it develops stout stems. Remember to allow at least a month after turning under before planting.

Winter rye (not Italian ryegrass which is different) is one of the hardiest cereals and is also drought tolerant. It can be planted early or late in fall, either by itself or with a legume such as hairy vetch or Austrian winter pea for adding nitrogen.

By itself it will scavenge soil nitrogen from last season and keep it from leaching over the winter. It grows well on sandy soils and is good for preventing wind erosion. Rye produces a lot of biomass adding to soil organic matter.

You can also leave a row of rye to shield early planted vegetables from spring winds. Peas, lettuce and other cold soil tolerant crops can now be seeded as soils should be well over 40 degrees F along most of the Front Range.

Photo credit: Winter rye closeup and in bed - Carl Wilson

New USDA Hardiness Zones Announced

Okay, so most vegetables don't overwinter (asparagus, rhubarb, Jerusalem artichoke and a few others being the exceptions). However, vegetable gardeners are concerned about climate and length of growing season. They are also interested in flowers and herbs for attracting pollinators to the vegetable garden whose persistence may be determined by hardiness zones. Fruit growers certainly have plant hardiness concerns.

What's exciting about the new, online 2012 USDA Hardiness Zone Map announced today? It's been updated to the Internet age with cool, online features. In addition to being able to put in your zip code and automatically get your zone, you can also enter your state name and see how climate works locally.

The coolest feature though is the Interactive Map that shows the streets in your area with the hardiness zones detailed. This is a vast improvement from previous maps where you had to guess your location on an all-to-generalized map. Be sure to click right on the map and use the +/- slide bar to zoom in to your neighborhood.

That said, what has changed with this revision? First, know that plant hardiness zones detail the average annual extreme minimum temperatures at a location for a given time period. In this revision that is the 30-year period from 1976-2005. These zones don't reflect historic lows that occurred before then or might occur in the future.

Compared to the previous 1990 map, the update shows most areas are a half-zone warmer (5 degrees F). In fact two new zones have been added to the U.S., 12 and 13. Each zone is a 10 degree F band that is subdivided into a and b. Most of the Front Range is now 5b with some 6a.

Grow on! - Hairy vetch

It's nice to see something green in the vegetable plots in winter and hairy vetch, Vicia villosa, performs well as a cover crop. It is is a high N producer, vigorous grower, very drought tolerant, prospers in low fertility and a wide range of soil conditions, and is winter hardy to zone 4 with snow cover.

One of the best things about fall planted hairy vetch is that it provides improvements in crop yields greater than the nitrogen added by it's symbiotic nitrogen-fixing bacteria alone. This may be due to root penetration that leads to better vegetable root development, physical soil improvement that allows a better air-moisture balance for crop roots in soil, improved soil biological activity or other reasons.

Note that hairy vetch doesn't build up long-term soil organic matter. It is a essentially a succulent plant that has a relatively low carbon to nitrogen ratio in the range of 8:1 to 15:1. Most benefits are realized by the first vegetable crop that follows in spring. For this reason it is often interplanted with winter rye, Secale cereale, that has a higher C:N ratio (ranging from 25:1 to 55:1) and thus breaks down more slowly. The combination planting results in some of the best of both worlds - N contribution plus short and longer term organic matter increase.

Hairy vetch growth is almost non-existent in mid-winter but will increase with lengthening days. Mow and turn it under at 25% bloom when N contribution will be maximized.

Note that freezing temperatures under 5 degree F can cause some winter kill if there is no snow cover. Temperatures in this range occurred along some parts of the Front Range December 5 and 6 and some damage may be seen. This is another reason to plant with hardy winter rye so an adequate spring yield of biomass can be gained. Next post will highlight workhorse winter rye as a cover crop.

Photo credit: Hairy vetch closeup - Carl Wilson

Season Endings and Beginnings

Vegetable Endings
With night temperatures predicted to drop into the thirties F this coming weekend, it's time to harvest what remains of tomatoes, peppers, eggplants and many other fruiting vegetables. Thirty degree temperatures are flavor killers for tomatoes anyway so using ripe fruit and ripening mature green or pink breaker fruit indoors is preferable.

Cover Crop Beginnings
Clearing plant refuse off the growing area now has another advantage. Mid-October is a good time to plant winter cover crops for soil improvement. Maintaining desirable levels of both organic matter and nitrogen in your soil is important for growing vegetables. Nonlegume cover crops help with organic matter and legumes can add both.

One common cover crop planted in our area is winter rye but there is a lot of confusion about what that is. Winter rye is cereal rye, Secale cereale, the same rye used for grain. Annual or Italian ryegrass, Lolium multiflorum, can be used as a cover crop in certain circumstances but winterkills in cold, dry Front Range conditions. Annual rye should be sown in early fall, so it's now late to plant.

Winter rye on the other hand is one of the hardiest of cereals and can be seeded later in fall. Growth is rapid in cool fall weather and its quick-growing, fibrous roots hold soil and leftover fertilizer well. It is also good at suppressing weeds.

Rye can also be sown with legumes in fall. Hairy vetch, Vicia villosa, is one of the most popular. It's winter hardy to zone 4 and can work in zone 3 with snow cover. It grows slowly but root growth continues over winter and vine growth quickens with arrival of spring. It tolerates poor soils (including sandy ones) and delivers a heavy contribution of nitrogen compliments of it's symbiotic nitrogen fixing bacteria.

A type of field pea (Pisum sativum subsp. arvense), Austrian winter pea, can also be used as a winter legume. It is not as cold hardy as hairy vetch and should be seeded in early fall. Plant it with a winter grain such as rye to protect pea roots and maximize winter survival. It prospers best with some winter moisture.

A rule of thumb is to plan for at least a month in spring after turning under cover crops to allow them to decompose before planting vegetables.

Photo credit: Tomato harvest and Rye/Hairy vetch seed - both Carl Wilson

Other root vegetables - parsnip

Parsnips are just now coming into their own with no need to worry about rushing to harvest before frost. In fact freezing actually improves root quality so bring on the cold weather. Roots can be dug as needed or stored moist (vented plastic bags) in the refigerator for a couple weeks so starches are converted to sugar for roots to have a better flavor.

Parsnips are grown from seed planted in early spring (April). 'Harris Model' and 'All American' are two standard varieties but most should grow well here. Fresh seed is a must as old seed germinates poorly. Like their parsley family cousin, carrots, seed takes 2 to 3 weeks to germinate. Seed is often over-planted because of poor germination and then seedlings thinned to 4-6 inches between plants.

This is a full season crop averaging 110 to 120 days (4 months) to mature. A deep, loose soil is a must just like carrots. Once top foliage grows to cover over, most weeds should cease being a problem. Supply steady moisture to avoid root disorders but note overwatering can cause forking and hairy roots. Moisture fluctuations produce cracking. Organic mulches (grass clippings or straw) in summer are helpful for weed and moisture control.

Parsnips are a different root vegetable to try for a variation from carrots and beets.

Photo credit: Parsnips in raised bed, harvested parsnip roots - both Carl Wilson

Seasonal roundup

Powdery mildew
With cooler weather comes a decline in production of summer squash and increase in powdery mildew on both summer and winter squash. Hopefully many fruit have been harvested or are near-ready for harvest. Photo is of powdery mildew on Kabocha winter squash. Powdery mildew decreases photosynthesis and weakens plants affecting nutrients available to form fruit and their flavor.

Control is mostly preventive through a full sun location and good air circulation. Water at the soil level rather than on leaves. Potassium bicarbonate (Remedy) can be used as a preventive or in the very early stages of infection. Some fungicides such as neem (Greenlight Powdery Mildew Killer) and horticultural oil do have some effect on killing existing infections.

Cabbage aphids
They're back......! Cabbage aphids thrive in cool fall weather and can be a real problem on savoy cabbage and Brussel sprouts (photo). They penetrate in and among the curled leaves and where sprouts set down in the leaf axil. Their feeding distorts and contaminates the harvest. Cabbage aphids overwinter on wild mustard family plants so weed control near the growing area is important.

Control is tough because of their waxy covering that makes these gray-green aphids appear bluish-white. Lady beetles don't like them because of the wax. Syrphid flies are another predator that may help. Unfortunately the activity of predators decreases late in the season when short days and cool temperatures reduce the activity of natural enemies. Parasitic wasps aid the cause but parasitized aphids tend to tightly stick to foliage compounding contamination problems.

Botanicals such as azadirachtin insect growth regulator, neem oil or pyrethins can be tried as well as horticultural oils when insect population thresholds warrant applications.

Destroy crop residue after harvest to minimize overwintering populations.

Photo credit: Powdery mildew on Kabocha squash, Cabbage aphid on Brussel sprouts - both Carl Wilson