Seed now and watch for cutworms

Now is the time to plant seeds of late summer and fall crops where earlier ones have been harvested. Chose 60 day or less crops (carrots, beets, bush beans, radishes, Swiss chard, New Zealand spinach) or ones that like to mature in cooler temperatures (lettuce, peas, spinach, kale, collards, Asian greens). Note that a nice option with greens is that they can be harvested at almost any stage of maturity in the event of a short growing season.

With a temperature in the nineties F, small seed will be hard to germinate Use seed germination fabric and water lightly but frequently.

One seed germination hazard that some people think is a spring but not summer pest in cutworms. Cutworms are caterpillars that cut and kill tender seedlings round the soil line.
The notorious "miller moth" that people in our area recognize in the adult flying form (photo above left) is Army cutworm in its larval caterpillar stage. (See above right photo).

Note that there are also climbing cutworms as the person who brought chomped basil leaves in for diagnosis today discovered. Beet armyworm (see photos adult left and larva right) is a climber active in mid to late summer that chews on a very wide variety of plants. Variegated cutworm is another (photos below).

Cutworms typically feed at night and hide in soil cracks, under dirt clods or seek other cover during the day. If you are going to find them, you have to go out after dark with a flashlight.

Cutworms are preyed upon by ground beetles, rove beetles, spiders, tachinid flies, parasitic wasps and other garden insects as well as toads and snakes. If natural enemies aren’t providing sufficient control, consider your weed situation. Cutworm moths are attracted to weeds for egg-laying.

Promote rapid seedling growth with good cultural practices (right amounts of water, loose soil, proper planting times, etc.) and use transplants. Transplants and older plants aren’t as tender and less likely to be damaged at the soil line. Note that climbing-type cutworms will find the tender leaves on top.

Protect tender transplants and seedlings with cutworm collars (cardboard, foil) or milk carton rings. Insecticide baits are available for cutworms. They are more targeted than whole-plant sprays which may kill beneficial insects as well as pests. Note that B.t. (Bacillus thuringiensis) natural insecticide is generally ineffective against cutworms.

Photo credit: Miller moth Whitney Cranshaw, CSU Extension; Army cutworm larva Frank Peairs, CSU Extension; Beet armyworm adult Merle Shepard & Gerald Carner & P.A.C. Ooi; Beet armyworm larva Frank Peairs, CSU Extension; Variegated cutworm adult Ian Kimber; Variegated cutworm larva Charles Olsen, USDA APHIS PPQ.

The Challenges of Summer Sowing

Mid-summer sowing of vegetable seed can be a challenge due to weed competition and warm soil temperature.

Weeds germinate quickly in summer and it can be difficult to tell the difference between weed seedlings and vegetable seedlings. One tip is to clear the soil surface of weed seeds by germinating and eliminating them. A week or more prior to sowing, water soil to germinate summer annual weeds such as purslane (see photo below left) and crabgrass and foxtail (photo below right).













Next use a sharp scuffle hoe to cut off the weeds from their roots, disturbing the soil as little as possible. Deep penetration of the soil will bring up additional weed seeds to germinate. Once the soil surface is cleared of weed plants, sow small seeded vegetables at the recommended shallow depth. Use germination fabric over them during germination (see March 6 post for how).

Warm soil temperatures can be a concern for germinating some seeds. The maximum soil temperature for germinating lettuce and spinach is 70 degrees F. The optimum temperature for germinating peas is 70 and many other vegetables 80 degrees F. Seeds become dormant at high temperatures.

Tips for avoiding warm temperature dormancy are to water soil before sowing and sow in the late afternoon so germination will begin overnight when soils are cooler. Shading the soil with seed germination fabric also helps.

Another tip is to pre-germinate seeds. The pea seeds (photo left) were soaked overnight indoors at room temperature (70 degrees F) in a moistened paper towel enclosed in a plastic bag. Do not soak longer or delicate seedling parts will be damaged in planting.

Pre-germinating small seedlings is more difficult. Solve this through fluid seeding. Germinate small seeds on a moistened paper towel in a closed plastic container kept indoors at 70 degrees F. Don’t allow seeds to germinate for more than a few days, only until they just break out of their seed coat. Wash germinating seed off the towel into a sieve with a gentle stream of room temperature water.

Gently stir germinated seeds into pre-prepared fluid seeding gel. The gel is made by dissolving 2 to 3 tablespoons of cornstarch in boiling water and cooling to room temperature. Add the gel-seed mixture to a plastic bag, seal, snip off one corner and gently squeeze the gel onto moistened soil. Cover as recommended and use seed germination fabric to shade. Keep fabric in place until green seedlings are readily apparent. Remove fabric and water carefully until seedlings are growing vigorously.

Crabgrass, purslane and soaked pea seed photos credit – Carl Wilson