Wednesday, January 28, 2009

The ‘birds and bees’ of saving seeds

Will saving seed from last year’s favorite vegetable pay off?

I don’t save seeds of F1 (first generation) hybrids because they lose hybrid vigor, don’t come true to type and most are patented anyway. Tomatoes, peppers and eggplants are ninety plus percent self pollinated and will come true to type if they are not a hybrid.

I save seeds of a favorite lettuce with success. Herbs such as dill self seed or can be collected and sown in either fall or spring.

What does and doesn’t work in terms of “the birds and bees” of the garden? Cucumbers do not cross with pumpkins, squash or melons but readily cross with each other.

Varieties of summer squash will cross with one another and with pumpkin. They don’t cross with winter squash. Cantaloupes do not cross with cucumbers, watermelons, pumpkins or squashes. Winter (fall) squash doesn’t cross with melons, pumpkins or summer squash. Sweet corn crosses with itself and also with field corn.

Potatoes by the way don’t cross with tomatoes. When potatoes produce fruit on the plants those aren’t a tomato, just a potato fruit. Propagate potatoes by saving and cutting tubers into seed pieces with an eye (sprout), not from potato fruit.

Many people prefer to buy seed and it generally is one of the least expensive investments in the garden.

I get a question every year from a Colorado gardener who claims they purchased seed and the plant produced a garden fruit monstrosity. Maybe a mix up occurred at the seed producer or more likely the seed of a hybid variety reverted to parental characteristics from last year's fruit dropped in the garden.

“Weird” crosses won’t show up in the year they are made. Crossed plant genetics are stored in the seed and don’t affect the fruit characteristics the year of the cross. The exception is sweet corn where crossing can affect the taste of the kernels that same year.

Certain crosses are genetically impossible because chromosome numbers aren’t the same, won’t successfully match up and can’t produce viable seed. See chromosome numbers below.

Vegetable chromosome counts
Like chromosome numbers need to be present to even think that crossing is possible (pumpkin and summer squash). Genetically distant and totally unlike plants won’t cross even if numbers happen to be the same (cantaloupe and tomato).

  • Cantaloupe 24
  • Cucumber 14
  • Potato 48
  • Pumpkin 40
  • Summer squash 40
  • Sweet corn 20
  • Tomato 24
  • Watermelon 22
  • Winter squash 24

[Pumpkin photo credit Carl Wilson]

Thursday, January 22, 2009

The wasp that cleaned out the caterpillars

Before you go thinking that honeybees mentioned in the last post are the reason you have so little caterpillar damage in your Front Range vegetable garden, remember European Paper Wasp. This wasp moved into Colorado in 2000 and has rapidly colonized Front Range landscapes. It is found on the West Slope but not generally in the mountains.

European paper wasps rear their young on live insects. They have become one of the most important natural controls of many kinds of Colorado garden insects. Most commonly they feed on caterpillars, including the larvae of hornworms and cabbageworms in the Colorado vegetable garden. On trees and shrubs tent caterpillars and sawfly larvae are commonly taken prey.

The European paper wasp is a black insect marked with yellow that is commonly mistaken for western yellowjacket. European paper wasp is slim in comparison to the somewhat blunter, more compact body form of yellowjackets. The long hind legs of paper wasps also tend to trail below when the insects are in flight unlike yellowjackets. They do not produce the nuisance problems for outdoor dining that are typical of western yellowjacket.

Check the Colorado State University Extension website for additional information and more photos of European paper wasp.

[European paper wasp photo credit: Whitney Cranshaw, Colorado State University,]

Bees do more than pollinate

The buzz of bees in flight causes some caterpillars to slow or cease feeding on plants.

German researchers Tautz and Rostas report in December’s Current Biology a 60 to 70 percent reduction in pepper leaves consumed by beet armyworm caterpillars in tented enclosures with honeybees than in tented enclosures without bees after two weeks.

Several caterpillars have evolved freeze-motion or drop-off-plant avoidance behaviors in response to predatory wasps. Sensory hairs on the caterpillars pick up vibrations from flying wasps and trigger the response. These behaviors are often combined with defensive coloration that blends caterpillars into the background color of the plant.

So bees can be beneficial to plants by slowing feeding even though honeybees are not predators of caterpillars. Note that pepper flowers (like those of tomatoes and eggplant) self-pollinate with wind movement, not from visits by bees or other insects.

This may be another reason to plant bee-attracting flowers in your Colorado edible garden in addition to wanting bees for pollinating squash, cucumbers, melons and pumpkins.

[Honeybee photo credit: David Cappaert, Michigan State University,]
[Beet armyworm photo credit: Frank Peairs, Colorado State University,]