Here is some helpful information on growing birdhouse gourds in a zone 5/6 area:
Birdhouse Gourds, Lagenaria siceraria (also known as Bottle Gourds) are the seeds most commonly used for gourd birdhouses. They require a full growing season, 100-120 days. The vines grow 25 ft. long and longer, and usually produce 10-12 gourds per vine. Vines can be trellised up, keep in mind that each gourd can easily weigh 10 pounds.
Start indoors 4-5 weeks before expected last frost date. In this area that would be the third week of April. Start in peat pots so there is little disturbance to the roots upon transplanting outside. Keep moist and give plenty of light.
Gourds need a lot of sun and a lot of room. Gourds are usually grown in ‘hills’ of well composted fertile soil. You can dig a hole about 12” deep, pour in some composted manure and top off with good potting soil. Plant seeds about 3” deep and cover with soil. Water in the morning so leaves are dry at night to help prevent leaf mildew. Water well throughout the growing season. Do not fertilize again or you will get more vine than gourds.
Gourds have male and female flowers. The female is distinguished by the bulb at the base of the flower, resembling a tiny gourd. You will get more gourds if you hand pollinate the female flowers by using a Q-Tip to get the pollen from the male and generously dusting the female flower’s interior. Male flowers generally bloom 2 weeks prior to the females. The females only bloom for about one day.
If growing gourds on the ground, it is best to put hay or straw underneath to prevent rot. You can also use a wooden board to give the gourd a nice flat bottom. If trellising, you may want to help support the gourds using pantyhose legs or net bags (like onion bags)
