Simple Ways to Improve Pollination

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Flowers for pollinators

It’s a fact of modern gardening life that there are fewer pollinators around than there used to be. The situation varies with location, but in most regions at least 60 percent of pollinators are gone, including many native bees. A recent survey of 131 farms in the US and Canada found that pollinator scarcity is already reducing yields of apples, blueberries, cherries, almonds, watermelon and pumpkin.

In your own garden, you can help reverse this trend by growing herbs and flowers that turn your yard into a pollinator hot spot, and allow space for ground-dwelling bees if you have an area you can leave undisturbed. But these measures may not be enough for garden vegetables that depend on pollinators for their success, which includes all of the cucumber family (cucumbers, melons, pumpkins and squash), and okra. Other vegetables do not rely on pollinators to develop their edible parts, but may need their help later on, when they flower and make seeds.

“Cucumber
A female cucumber blossom, ready for pollination

Parthenocarpic Cucumbers

All members of the cucurbit family develop male and female flowers, and they depend on bees, flies and beetles to move sticky pollen grains between the two. Female flowers are open and fertile for only one day, during which time eight to twelve pollinator visits are needed for good fruit set. This is a real problem when there is a shortage of bees, flowers, or both.

Ready for some good news? With cucumbers there is an easy solution - traditionally-bred parthenocarpic cucumber varieties, which set fruit without help from insect pollinators. Popular for growing in greenhouses and polytunnels, parthenocarpic cucumbers can be found in a range of types. ‘Sweet Success’ is a big, burpless slicer, ‘Little Leaf’ is a disease-resistant pickler, and ‘Tyria’ is a long, thin-skinned European type. Even if you grow only two plants (which may not produce enough flowers to attract pollinators) you can get a good crop with these and other parthenocarpic cucumber varieties.

“Bee
In the US, native squash bees emerge in midsummer

Better Pollination for Summer Squash

When your summer squash blooms nicely enough, but the little squash shrivel at the ends, the flowers did not get adequately pollinated. You can hand-pollinate squash or pumpkins by transferring pollen from male to female blooms with a dry paintbrush, which must be done three times a day for best results. In my garden, I have found that squash pollinators emerge in midsummer, so running my crop late rather than early reduces my hand-pollinating chores.

As with cucumbers, a few summer squash varieties are at least partially self-fertile. More than 15 years ago, agricultural researchers noticed that some summer squash set fruit without pollination, and field trials have since revealed a short list of parthenocarpic squash varieties. Self-fertile green courgettes include ‘Parthenon’ and ‘Cavili’; ‘Easy Pick Gold’ yellow squash also will set fruit without pollinators. The size and shape of the fruits improves when pollinators are present, but these parthenocarpic squash can go it alone if they must.

Unfortunately, there are no known varieties of pumpkin or winter squash with parthenocarpic tendencies. With those crops, hand-pollination is the best option when insects are not doing the job.

“Watermelon”
Native bees and honeybees pollinate watermelons

Grow Flowers with Melons

No breakthroughs are on the horizon for muskmelons, cantaloupes or watermelons, either, for which honeybees are very efficient pollinators. Yet studies in Brazil and the USA have revealed that native bees, including common sweat bees, also are primary pollinators of melons. The best way to enlist the help of these little buzzers is to grow blooming flowers near your melon patch, timed to bloom along with your melons. Easy, fast-blooming flowers for this purpose include sulphuur cosmos, gaillardia, and zinnias.

Should you decide to hand-pollinate melons in a small planting, keep in mind that the flowers expect 8 to 10 insect visits in a four-hour period. Use a dry artist's paintbrush to mimic this action several times over the course of a morning.

“Okra”
Small pod size is associated with poor pollination in okra

Small plantings of okra can be hand-pollinated, too, preferably between 10am and noon. Though okra is often called self-fertile, several studies have shown that insect visits vastly improve the size and seed fill of okra pods.

You may not need to hand-pollinate at all if you develop your garden as a pollinator hot spot. In an extensive survey of 360 sites in Britain, home gardens and allotments proved themselves as pollinator sanctuaries. Why settle for pollinator decline when you can do something about it?

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