Beth Jarvis, Yard & Garden Line
Gardeners in Minnesota have reported uneven fruit set in some garden crops. Peppers, tomatoes and squash are common problem plants. It appears the spike in summer's heat may have been the reason.
Tomatoes, peppers, eggplants and potatoes are all members of the plant family Solanaceae, the nightshade family. (Chinese lanterns/tomatillos/ground cherries are also members as are belladonna, nightshade weeds, Jimson weed, tobacco and the annual nicotiana.)
Peppers:
What does temperature have to do with poor pepper set? Peppers are frost sensitive so they should be the very last thing to go into the garden in spring. Putting them out too early, before the soil's warmed, may inhibit their development. However, they will tolerate warm weather better than their tomato cousins. A pepper's idea of ideal weather is 68-77 F and peppers grow better with night time temperatures that don't exceed 68F. Small fruited cultivars are more tolerant of temperature extremes.
Peppers do not respond to day length but simply begin to bloom 30 to 60 days after planting and it usually takes a month for a blossom to turn into a full size pepper.
It won't matter how many bees you have around because peppers are self pollinators. Pollen production is adversely affected, resulting in unfertilized flowers, at temperature under 60.8F or over 89.6F.
Even watering is important to peppers because, even though they're somewhat drought tolerant, moisture stress during flowering may cause small fruit or flowers to drop off.
Tomatoes:
For heavy fruit set in tomatoes, night temperature is more important than day temperature. Tomatoes like wide swings in temperatures day to night with 77-86 F days and 60.8 to 68 night as optimal. Fruit set is poor when temperatures hit over 86C or below 59C. If night temperatures exceed 75 or daytime temperatures reach 100+, tomatoes will drop blossoms or not set fruit.
High temperatures raise havoc with tomato flower fertilization by not only reducing pollen production but also reducing the viability of the ovule (plant ovary). Poor pollination can be a culprit for poor fruit for some crops but not tomatoes or their cousins.
If your botany's a bit rusty, think of the female flower parts as a bud vase. The ovule, which becomes the fruit is the bowl of the vase, the neck is the style and the stigma is the mouth of the vase. Pollen has to land on the stigma, germinate and grow down the style to the ovule for pollination to occur. Tomatoes have perfect flowers which means the flowers have both male and female flower parts. With many perfect flowers, the staminate, or male flower parts are those things that look like swamp cattails or hotdogs on a stick. The anther is the hotdog and the filament is the stick. They generally surround the pistilate or female flower parts-- the bud vase. With tomatoes, the anthers have partially fused and actually form an arch over the stigma, which makes it pretty hard for a tomato flower to not get pollinated, because the pollen is right there. In fact, if you want to help pollinate your tomatoes, all you have to do is to shake them a little bit. It's important to have healthy tomato plants at the time of fruit set because once the fruit starts to form, the plants' resources will be routed mainly to the fruit. Small, under-developed plants don't yield well.
Squash:
Squash, pumpkins, melons, cucumbers are all related and referred to as cucurbits. Most of them have separate male and female flowers, produced on the same plant (monoecious). Because the ovary of the female flower develops into the fruit–cucumber, zucchini, etc. you can generally easily tell the female flowers because they're attached to a miniature fruit. People sometimes think there's something wrong with a squash that drops small fruit. It's simply a female flower that was not pollinated. Unlike tomatoes, cucurbits are insect pollinated.
Cucurbits generally produce male flowers first, followed by the female flowers. Generally there are more males flowers than female flowers, possibly as many as 25:1, depending on species.
Plant hormones affect flower production and these hormones can be affected by weather. Warm days and long days prompt males flower production while cooler temperatures and shorter days favor female flower production, but, obviously, there is some overlap as we are generally richly blessed with cucumbers and summer squash.
No, it's not your imagination, summer squash plants, like zucchini, do produce more fruit than winter squash. For maximum yield from cucumbers and summer squash, pick early and often.
