Question
Hi,
I live in San Francisco and have started a small garden.  Once  the zucchinis get about a couple of inches long they always wither away and die.  Do you know why?

Answer
Richard, when vegetables shrivel and fall from the stem, it is usually an indication of inconsistent watering or that the plant is not being fully pollinated.

Soil that is composed primarily of clay will often not drain properly, resulting in the plant's roots suffocating and not absorbing the nutrients needed for good growth. The same will happen if your area is receiving too much rain or your are supplementing the garden with too much water. The key is to supply only enough water to fill the plant's need of 1.5" of water per week. You should also mulch the plants with compost or shredded leaves to help retain moisture.

Secondly, it is very important that the soil be amended with organic matter. These materials include compost, peat moss, aged manure, and shredded leaves. These will help improve the tilth of the soil, improve drainage, and provide constant fertilization throughout the growing season.

Finally, it is very important that the plants are being fully pollinated. Squash will provide small fruits even if no pollination has occurred. But these will only grow 1-2 inches and then quickly die.

I always recommend growing bright annuals around fruiting plants to entice bees to the area. I personally grow marigolds and zinnias in the same bed. Not only do they attract bees, but the marigolds will deter other pests, such as rabbits, with their pungent smell.

In the meantime, you can hand-pollinate the plants with a Q-tip or small paint brush by brushing the pollen from the stamen of the male flower and then transferring it to the female flower. The female blossom is easily identified because it has a swollen growth behind the flower that will eventually mature into a squash.

I hope this answered your question. Please write again if I can ever be of assistance.

Regards,

Mike