Pollination of Vegetable Crops in a Warming Climate

Pollination is the movement of pollen from male to female flower parts of sexually reproducing plants. It is often accomplished by wind and insects and results in the development of some type of fruit containing seeds for the species’ continuation. Farmers and gardeners in the mid-Atlantic are finding that high day and evening temperatures can cause vegetable plants to drop flowers and small fruits or produce deformed and under-sized fruits. This  problem has been observed in crops like bean, tomato, and pepper (mostly self-fertile; individual flowers can pollinate themselves), and in crops like squash and pumpkin (require cross-pollination between flowers).

How do high temperatures affect pollination?

All fruiting plants have an optimal temperature range for the pollination/fertilization process. High temperatures can reduce pollen production, prevent anthers from releasing pollen, kill pollen outright, and interfere with the pollen tubes that serve as conduits for uniting sperm cells and eggs (fertilization) inside undeveloped seeds (ovules). High temperatures can even injure flowers before they open. Night temperatures are increasing at a faster rate than day temperatures as a result of climate change, and seem to be most responsible for these pollination problems.

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Fighting CO2 on a Balcony

It’s well known that atmospheric carbon dioxide (CO2) is one of the leading causes of climate change and that plants play a role in mitigating its impact by taking in carbon dioxide and releasing oxygen. But did you know that even the smallest gardens can make a difference? Container gardens can be effective ways for adding plants to the ecosystem, nurturing pollinators and other beneficial insects, and even providing food for your table.

A container garden with mixed perennials and annuals provides beauty, food, and habitat. Photo: Pat Wilson

High above Columbia’s Wilde Lake at the Residences at Vantage Point, long-time gardener Barbara Schuyler continues the gardening that was her passion when she and her wife Pat Wilson lived on a rural property. More than 90 containers of shrubs, annuals, perennials, and vegetables grace two balconies that face west and south.

Barbara’s approach to container gardening

Shrubs and perennials comprise a significant part of the garden. Hardy perennials winter over and are especially effective at drawing down carbon dioxide. Some of the perennials, like the orange butterfly milkweed (Asclepias tuberosa) pictured below, are natives. Native plants are well-suited to our climate, require less care than imported species, and support native insects. Barbara’s native plants also include lots of Rudbeckia, some Echinacea, and several Heuchera

orange and blue flowers planted in a container garden
Native butterfly milkweed (orange flowers) combines beautifully with the blue-theme flowers. Photo: Barbara Schuyler

In addition, each year Barbara and Pat decide on a theme and collect annual seeds to plant when the temperature warms up each spring. Last year, the blue flower theme provided a consistent backdrop for the foliage and flowers of other plants.

She uses regular potting soil and each spring spreads the old soil on a tarp to remove roots and debris and returns it to the pots with a portion of fresh potting soil added.

Her collection of containers is eclectic and includes salad tables for vegetables, wine barrels, ceramic and plastic pots. A container exchange in the building helps many patio gardeners find pots that meet specific size and decorative needs. Reusing and sharing materials can help reduce CO2 associated with buying and shipping new products. She also tried felt bags but was not pleased with the results.

spray handle attached to kitchen sink
Photo: Christine Hipple

Watering 90 containers with a watering can during dry spells would be a major challenge, so Barbara purchased a garden hose sink adapter to allow her to connect a lightweight flexible hose to the kitchen sink.  

One big advantage of balcony gardens is that deer can’t get to them, though she has seen a squirrel or two.

Benefits

Visiting her garden every morning is a joy in itself. It provides Barbara the opportunity to be present with her plants, be aware of their needs, and appreciate what they offer throughout the seasons.

Even at this extreme height, pollinators are attracted to and supported by the garden. Three species of bees, several types of moths, and even a few monarchs have been spotted.

Lettuce and arugula do well in pots, and along with cherry tomatoes provide healthy super-local produce — yet another reduction in their carbon footprint. One lesson Barbara’s learned about cherry tomatoes is not to crowd them. Plant just one to a large pot and prune assertively to be sure the energy goes into making tomatoes rather than excess foliage and that there’s sufficient air circulation.

cherry tomatoes ripening
Growing some food at home is fun and helps reduce the carbon footprint of food transport. Photo: Barbara Schuyler

While there’s some level of physical work involved, container gardening is within the reach of nearly everyone – no matter your available space, skill level, physical abilities, or budget. Start small. Share stories, plants, and pots with other gardeners, and enjoy the benefits for yourself, your community, and the planet!

Are you taking any steps in your garden to help mitigate and adapt to climate change? Have a story to share? Let us know! Leave a comment or contact us.

By Christine Hipple, University of Maryland Extension Master Gardener, Howard County, Maryland