Q: I’m new to vegetable gardening and want to know when to start in the Denver metro area.
A. Many vegetable gardeners have already planted the most hardy, cool-season vegetables, including peas, onions, lettuce, radish and spinach, but it is not too late. With peas, you reap a 50 percent higher yield by planting April 1 as opposed to delaying until May 1.
Semi-hardy vegetables can be sown in late April. They include beets, carrots, potatoes, Swiss chard and cauliflower.
Delay planting warm-season vegetables until May. By midmonth you can plant beans, corn, cucumbers and summer squash. For those intolerant of the lightest frost, don’t plant until the end of May, when the frost danger is well past. This very tender group includes tomatoes, eggplant, peppers, winter squash, cantaloupe, watermelons and pumpkins.
Q. How do I control pesky aphids on my cabbage before they become a problem?
A. Cabbage and turnip aphids feed on members of the cabbage family, including broccoli and kale. They often spend the winter as eggs on wild or cultivated cabbage and mustard family plants.
Pull and destroy mustard family weeds near your garden this spring. If winged forms do fly in and find your plants, allow natural insect predators and parasites to feed on them. As with any aphid, try to wash them off with a stream of water. Several insecticides available at garden centers also can be useful in combination with these other measures.
Q. I had problems with tan blotches on my spinach leaves last spring. What am I doing wrong?
A. This may have been insect damage caused by spinach leaf miner. The immature maggot stage burrows within leaves of spinach, beets and chard, causing blotchy dead patches. The remainder of the leaf is edible.
This insect overwinters in the soil, emerging in midspring. It flies to young plants and lays white egg masses on the undersides of leaves. The maggot hatches to tunnel into the leaves for two to three weeks before dropping to the ground to pupate.
If you plant your spinach in a new area where leaf miners won’t be emerging from the ground, use floating row cover fabric to cover your plants and exclude adult flies. Regularly inspect leaves for egg masses on the undersides and crush any you find before they hatch.
If you find larvae tunneling within the leaves, pick and destroy the leaves because insects will continue to live there. Very early spring plantings and fall plantings tend to escape damage.
Carl Wilson is Colorado State University Cooperative Extension Horticulturist in Denver. For information, visit planttalk.org or AnswerLink.info.
