Blooming Basics:
Tomatoes and Squash

Do you know the basics of blooming? If not, you are probably very distressed by now that your bloomers may be dropping! That's right, friends, blooms are falling from plants and it’s really not your fault. Some vegetable crops just naturally need their sexual parts manipulated before production will occur in early spring. The vegetables that cause the most problems are vine crops such as squash, cantaloupe, cucumber and watermelon, as well as such garden favorites as tomato, pepper and eggplant.

The vine crops mentioned are monecious plants. That means that both male and female organs exist on the same plant. The problem is that the flowers with the male parts are separate from the flowers with the female parts. To complicate matters even further, at this time of the year, both male and female flowers may not be on the plant at the same time. Since it "takes 2 to tango", if the female appears first, the fruit will fall off the plant because it lacks pollination by the male. And, if that were not enough, many times when the male and female are both present, the male is impotent! The pollen that is produced is sticky and not readily adaptable to wind pollination. Pollen transferal from flower to flower relies principally on honeybees. Without good bee activity, the fruit set will be dramatically reduced.

Each fruit of the vine crop produced from a female flower contains several hundred seeds which required a transfer of several hundred pollen grains. The female flower is only open for 1 day and is most receptive between the hours of 9 am and 4pm. During this time, the flower must receive about 15 bee visits for maximum pollination. Unfertilized or poorly fertilized flowers abort and fall from the vine within 1 or 2 days. Fortunately, the vine crops have some 100 female flowers produced during a life cycle.

Each flower could potentially become a harvested fruit. Fruits formed near the crown (stem area) of the plant are the most desirable, as they usually are larger, mature earlier and contain more sugar. For this reason, it is important to have bees present at first bloom. Usually, male flowers are formed first and the bees can gather pollen from these flowers and establish regular feeding and watering patterns before the female flowers are developed. This creates the best opportunity for the crop to produce crown- set fruits.

As mentioned earlier, the male bloom appears first. "How does one distinguish a female from a male bloom?" you ask (with some hesitation). The female bloom has a small fruit attached to the base of the flower. The male bloom is just a plain flower attached to the plant by a green stem.

If you, the gardener, lacks a source of such pollinating insects, or you continually kill them by spraying insecticides during flight periods, inadequate pollination and fruit drop will occur. During seasons of peak pollination, spray insecticides late in the afternoon to avoid problems.

If you do not have bees, you can hand pollinate blooms. This involves taking a male bloom and rubbing it in a female bloom early in the morning. This will effectively transfer the male pollen to the female bloom.

The bloom time of squash also signals the beginning of another squash-growing, task-squash vine-borer control period. Just as blooming begins, the reddish, wasp-like moths visit plants and deposit eggs which hatch into the white borer. In the spring, plants will be in the bloom stage before eggs are deposited. So, you can enjoy some harvest before the enlarging borer larvae can devastate the inside of the vine until it dies. In the fall, seedlings are small when they are attacked, so feeding vine-borers will kill plants faster. Many times, a fall planting of squash will be killed even before seedlings are 6 inches tall.

A protective dome cover made of screen can be placed over squash seedlings to physically keep the moth from depositing eggs until plants are larger. However, plants soon outgrow such devices. Dusting or spraying main stalks with Sevin every 3 days (which has also been recommended) can stimulate spider mite populations. Products containing the active ingredient endosulfan, commonly referred to as Thiodan, are more effective. Endosulfan is sold as Garden Bug Killer and Thiodan Garden Dust.

Since endosulfan is effective for a longer period of time, it is more successful in combating the destructive trio—vine-borers, squash bugs and stink bugs—with weekly applications. Endosulfan can be used on squash, potatoes, peas, tomatoes, peppers, eggplant, beans, celery, cabbage, broccoli, carrots, Brussels sprouts, cauliflower, lettuce, spinach, collards, mustard greens and kale. No pesticide is perfect. All should be used as label instructions direct. But the exciting thing about endosulfan is that it offers an opportunity to rid the most damaging of the garden insects without stimulating spider mites. Simply dust the main squash stem—not the entire plant—weekly to eliminate vine=borer devastation. Tomato, pepper and eggplant blooms drop off plants because of another type of pollination problem. The tomato is hermaphroditic which means that both male and female parts exist in the same flower. So how could it have a pollination problem?

The pollination problem of these crops exists because the female part of the flower (pistil), which must be pollinated, is located above the male flower parts which produce pollen. If this pollen is inactivate because of hot temperatures, or made sticky by cool, cloudy conditions, the female flower part will not be pollinated, and the entire flower and potential tomato will drop off.

Tomato, peppers and eggplant flowers are wind or mechanically pollinated, so gardeners don't have to rely on bees. The flowers can be artificially set, or made to stay on the plants, by use of blossom-set hormones sold in local nurseries. These hormones are effective fruit-setters only during early spring when cool, cloudy temperatures are the villains. Tomatoes that are artificially set with hormone sprays will have fewer seed. These are not test tube babies but can certainly claim conception by artificial means.

So don't become alarmed if your bloomers are dropping—do something about it, now that you know the basics of blooming.