If you live in Denver, you probably deal with gardening conditions atypical of those described in gardening books. With its rocky, clay soil, Denver lies inside what some gardeners call a "heat island." This means conditions in the city are warmer than those in the surrounding Colorado region. While the areas outside of Denver fall in zone 5, Denver itself is USDA zone 6. Gardeners must adjust their cultivating practices accordingly.
Test your soil to determine the pH with a home testing kit, which you can purchase in your local garden center. Although the process for testing soil varies among kits, each kit includes instructions.
Purchase soil amendments to improve the structure of your soil. Denver soils need plenty of organic amendments such as compost, peat moss and well-rotted manure. In addition, you can lower your pH with lime or raise it using sulfur.
Break up your soil to a depth of 8 inches using a rototiller. Remove any large rocks you find. Spread soil amendments on the soil to a depth of 4 inches. Mix the amendments with the soil by passing the rototiller over them again.
Plant seeds two weeks before the last frost of the year. Plant bedding plants any time after the last frost date. For warm-season plants such as tomatoes, select early-bearing hybrids and plant them as bedding plants after the last frost date. This way you will have a good crop of vegetables before the first frost of the year. Denver is typically frost-free from early May to early October.
Dig furrows into your soil with a hoe. Plant your vegetable seeds twice as deep as their diameter and cover them with soil. For bedding plants, dig a planting pocket twice as wide as the plant's root ball. Place the plant in the planting pocket and cover with soil.
Check your plants daily to see if they need water. Plants should remain as damp as a wrung-out sponge.