Ron Kujawski | Garden Journal: When should cover crops be tilled under?


About a month ago, I discussed in this column the mid-summer planting of green manure or cover crops to fill in garden spaces vacated by the harvest of peas, spinach, turnips and other early season crops. The cover crops mentioned were berseem clover, mustard, buckwheat and sudangrass. All of these are growing well right now, but the question is "When do I till under these crops?"

Berseem clover is not winter-hardy and will be killed by hard freezes. The dead plants should be left on the soil surface through winter and then tilled under in early spring when soils are dry enough to be worked.

Buckwheat is usually mowed down with a sickle or string trimmer once it comes into flower. The mowed plants may be left on the soil through winter and tilled in spring.

Mustard is mowed just as it begins to flower. I may not wait until then since I want to mow it down and till it under about two weeks before I plant garlic in late October in the same area as the mustard grew. The reason being that mustard is a natural biofumigant, that is, it releases a chemical that kills soil-borne pathogens and nematodes, which may infect garlic. The two-week waiting period before planting garlic is needed to allow the mustard to decompose.

The other cover crop I mentioned is sudangrass. It is capable or growing to more than 6 feet tall. However, in a home garden, it is best to mow it when 20 to 30 inches tall since taller sudangrass is fibrous and difficult to till and work into the soil. After mowing, leave the cut grass on the soil surface where it will suppress any weed growth through fall. Turn it under in early spring.

There's still time to sow additional cover crops this month and into early October. Most often, it is winter-hardy cereal grains that are planted as cover crops now. The most common fall seeded cover crops are winter rye and winter wheat. They'll survive the winter and assume growth again in early spring. It is best to till under these crops as early as possible to give them time to decompose before spring planting of vegetable crops. Again, allow about two weeks for the decomposition to be completed before planting vegetables.

The advantages of planting a green manure or cover crop this month and into early October, as garden space opens up with the harvest of vegetable crops, are many. They suppress weed growth; they take up and store mineral nutrients that would otherwise leach from the soil; they reduce soil erosion due to wind and rain; and they eventually contribute significant amounts of organic matter to enrich the soil and improve soil structure.

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When not tilling or planting cover crops, turn your attention to these tasks this week:

- Cure harvested pumpkins by placing them in an area with a temperature of 75 to 85 degrees F for about two weeks. Then store them out of direct sunlight in a cool, dry location of 50 to 60 degrees F. They should keep for up to three months. Gourds and winter squash can be cured and stored in the same manner as pumpkins.

- Save some plum tomatoes for drying. Drying or dehydrating tomatoes can be done using the classic sun-drying approach, but that will take many days and a reliable stretch of sunny weather ... and perhaps a trip to Italy. The easier way is to dry tomatoes using a dehydrator or drying them in the oven. Begin the process by slicing the tomatoes in half lengthwise. You could squeeze out the seeds and excess moisture from the tomatoes, but I don't bother. If oven drying, set the oven temperature as low as possible, but no higher than 200 degrees F. Arrange the sliced tomatoes on a drying rack and place the rack in the oven. I prefer an electric dehydrator, simply for the ease of use, and set the temperature dial at 135 F. The length of time to complete drying will depend on the size and moisture content of the tomatoes. Drying is completed when the tomatoes no longer feel moist and are a little leathery. Sometimes, I will dehydrate tomatoes until they are crisp. These tomatoes will then be ground in a coffee grinder to make tomato powder. We've found that the best way to store dried tomatoes is by way of vacuum sealing in plastic bags. They'll keep for a year or more. If planning to make the dehydration of tomatoes an annual event, I suggest growing the Italian heirloom variety, Principe Borghese. The fruit are small, about 2 inches in length, and retain a rich, sweet flavor when dried. You can find this variety in most seed catalogs.

- Plant perennials, trees and shrubs through this month. While we most often think of spring as the ideal planting season, late summer and early fall are also favorable times for planting. Shorter days and cooler air temperatures mean less stress on plants. On the other hand, soils are still warm and promote good root development. These same environmental conditions favor digging, dividing and replanting herbaceous perennials which have completed their bloom time.

- Force Christmas cactus into bloom by exposing the plant to short days beginning today. Keep the plant in total darkness for 12 to 14 hours each night until flower buds form. Ideally, the temperature for forcing Christmas cactus should be 60 degrees F or lower. A cool corner of the basement may do the trick.

- Cover the heads of sunflowers with cheesecloth to prevent birds from getting at the seeds. Otherwise, cut off the seed heads — with a section of stem — when they are completely brown. Hang the seed heads in a dry, airy spot to dry. Drying is completed when the seeds easily separate from the head when rubbed.


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