Scarlet runner beans do best cool summer weather

Vines will likely begin producing pods as temperature cools

Published Aug 12, 2025 • Last updated 1 hour ago • 2 minute read

Runner beans, unlike other green beans (pole and bush) grow best and are at their most productive in cool summer weather, says Helen Chesnut. Photo by Monique Pare

Q. Our scarlet runner beans have grown well and produced many flowers, but few of the blooms have turned into beans. Instead, they simply fall off the tall vines. Why?

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A. I am asked this question almost every summer, at least during summers that deliver periods of hot, sunny weather. Runner beans, unlike other green beans (pole and bush) grow best and are at their most productive in cool summer weather.

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They need a cool, consistently moist root run.

Because they prefer cool conditions, runner beans can also be planted ahead of pole and bush green beans.

Also unlike pole and bush beans, runner beans require pollination by bees or hummingbirds.

The blossom drop you describe happens when the flowers are not pollinated or the weather is too hot.

Don’t give up on them. As the weather cools the vines will likely begin producing pods. Meanwhile, keep them well watered and lay a moisture-retaining, heat-deflecting mulch (dry leaves, chopped straw) over the root area.

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Q. On a recent tour through a friend’s garden, I spotted a real curiosity — a round, pale yellow fruit-like structure growing on a vine. My friend identified it as a “sort of” cucumber, grown from seeds she was given. Is this a new type of vegetable?

A. No, it is actually an heirloom cucumber dating back to the 1800s. This variety of cucumber is commonly called Lemon, but as is usual with older and heirloom varieties, many different strains, selected by different growers, exist under other names — like Apple, Crystal Apple, and Crystal Lemon.

The fruits are round and the size of a small apple. The skin is lemon coloured, the flesh lime green. These little cucumbers have a clean, crisp texture and a sweet, mild flavour that never turns bitter even with age.

The strain I’m growing this year is simply “Lemon” from Salt Spring Seeds. I always grow at least one vine, to provide refreshing little summer garden snacks.