Although it may seem that vegetable gardens have just begun growing well and planting is done, it’s time to seed crops for fall harvest in July or early August. Sixty day crops planted in July will mature in September as weather is cooling.
Look at seed packets and note the days to harvest. Count back from the first fall frost date, October 11 for the Denver area. With cool season vegetables note that many tolerate the first light frosts of fall very well and an extended harvest period can be expected. Warm season vegetables must be planted to mature well before frost when temperatures remain warm.
Here are some vegetable planting suggestions listed with their typical days to harvest. Cool season vegetables such as peas (65), cabbage (85), collards (55), broccoli (65), kale (60), spinach (40), lettuce (60) and endive (45) are good candidates. Root vegetables such as beets (60), carrots (70) and turnips (50) can be planted in July. Even some fruiting vegetables such as bush beans (60) and cucumbers (55) can still be planted if done by mid-July. The very short season radish (30) can be planted into August with success.
Note that peas planted for fall harvest are prone to powdery mildew. Choose powdery mildew resistant varieties. Be sure to have support for them to climb off the ground insuring good air circulation. Often harvests are reduced as compared to spring plantings.
Planting fall crops in “succession” where other spring crops have been harvested is a way to extend harvests past the first frosts and maximize yields from gardens.