Cucumbers, Pumpkins, Squash, and Melons

Cucumbers, pumpkins, squash, and melons are warm weather plants. Their growth, yield, and quality are best when days are warm and sunny, and the season is long. Cucumbers and summer squash usually require 50 to 65 days for first production. Melons need 80 to 95 days. 

Delay planting until a week after the average last spring frost date for the area. If the weather is chilly, delay longer. Ideally, the temperature of the soil at a 2-inch depth should be 60 degrees F. 

In Colorado, temperature and length of growing season are closely related to elevation. At elevations below 5,000 feet, all these crops generally are productive. Above 5,000 feet, cucumbers and summer squash are most satisfactory because they mature in a relatively short time. 

It is possible to lengthen the growing season by starting seedlings indoors and transplanting them into the garden when the weather warms. None of these plants tolerate disturbance of their root system. The only feasible method for transplanting is to start seedlings in pots and move them without damage to the roots. 

Planting

These plants are usually planted in hills or mounds so excess water drains away from the seedlings. Plant five or six seeds together in hills 4 to 6 feet apart. Cover the seeds with about 1 inch of soil. After emergence, thin each hill to the two or three strongest seedlings. Clip plants during thinning to avoid disturbing the roots nearby seedlings. Cucumbers can be planted next to fences or trellises, to which they will cling. 

A good general fertilizer rate for cucurbits is 1 pound of nitrogen per 1,000 square feet. This may be obtained with 2 pounds of urea, which contains about 46 percent active ingredients. Work the fertilizer into the top 4 inches of soil prior to planting the seed. 

If organic fertilizers are preferred, use 2 bushels of manure or 1 cup of bone meal and 1 cup of dried blood per 100 square feet. These organic fertilizers also can be divided up and worked in around the hills rather than spread over the whole area. 

Keep the soil consistently moist, but avoid overwatering as this can hinder germination. As the plants grow and the weather becomes warmer, more water will be required. When the plants cover the surface of the soil and in warm weather, the plants may use 1 to 1 1/2 inches of water per week. It is better to irrigate thoroughly every five to seven days than to sprinkle lightly every day. Temporary wilting in the heat of the afternoon is common, but wilted plants in the morning is a distress signal — water them. 

Pests

These vegetables are subject to attack by several insects, each of which has several options for control. Produce healthy plants and deal with insect problems when they arise. 

Before attempting control, positively identify the target pest. The best pest management practice is to use the least damaging pest control methods as possible first. These include hand-picking, strong jets of water, and insecticidal soaps. Should further control be needed, find a chemical option that is labeled for use on both the crop and the insect. 

When diseases strike, assess the situation. If only a few leaves are affected, remove them. This may solve the problem. If symptoms are more widespread, then chemical control may be in order. 

Among cucumber diseases, the most likely is Angular Leaf Spot. This bacterial disease causes angular-shaped lesions on the leaves and attacks the fruit. These lesions become necrotic, producing the angular areas which give the disease its name. The first course of action is to stimulate growth by applying nitrogen and water. Reduce competition for sunlight and space by removing competing foliage. If six uninfected leaves can be maintained at the ends of the vines, the plants will remain productive. After having accomplished this, the foliage may be sprayed with a copper compound to control the disease. 

The most common foliar disease of cucumbers, squash, and melons is powdery mildew. Remove affected leaves as soon as symptoms are noticed and avoid practices that increase humidity around the leaves, such as watering in the evening and overhead watering.  

Fruit Set

Gardeners often become concerned when these plants begin to flower but no fruits are produced. Most varieties produce several male flowers before female flowers appear and fruits are set. It is easy to differentiate between male and female flowers. 

If female flowers are being produced, there are two common reasons for failure to set fruit: 

1. If there are fruits already growing on the plant, they will inhibit further fruit set until they mature or are harvested. 
2. These plants depend upon insects, mainly bees, for pollination. If insect activity is very low, fruits may not set due to lack of pollination. Insufficient pollination sometimes results in deformed fruits. Consider hand pollination if this is an issue. 

Harvesting

Cucumbers and summer squash are harvested and used as immature fruit. Time of harvesting depends on fruit size. For summer squash, fruits about 6 inches long are of prime quality. Cucumbers for slicing usually are harvested at about 6 to 8 inches. For pickling it is wise to select the size best for the kind of pickles desired. Harvest often and thoroughly. Fruits left on the plants will inhibit further fruit set until they mature. 

Winter squash and pumpkins are harvested when they are mature. The skin will harden so it can’t be penetrated easily by a thumbnail. These mature fruits can be stored most of the winter if protected from freezing. 

Winter melons (casaba, crenshaw, honeydew) also can be stored for several weeks if harvested before they begin to soften. 

Harvest watermelons and cantaloupes when fully ripe. They don’t store well. Watermelon ripeness can be judged by thumping — a dull sound indicates ripe, a ringing sound not ripe — or by a buttery-yellow color of the rind where the fruit rests on the ground. 

Ripe cantaloupes slip easily from the vine when picked up; unripe ones require more force to pull them away from the vine. The background color of cantaloupes also changes from grayish green to yellowish as they ripen, and the characteristic musky odor develops. 

Reference: CSU Fact Sheet 7.609