All Those Flowers and Not One Zucchini? Check the Calendar First

Quick answer: If the plant is green and flowering but nothing's growing, it's usually one of four things: too early, too hot, too much nitrogen, or too few pollinators. Wait two weeks, then pollinate by hand with a paintbrush. That fixes most of it for about two dollars.

Your plant isn't failing. It's early.

Squash plants carry separate male and female flowers. The males come first, often a week or two ahead of the females. So you get a plant the size of a card table, covered in big yellow blooms, and not a single squash.

Tell them apart by looking behind the petals. A male sits on a thin, straight stem. A female has a tiny swollen fruit at the base, a baby zucchini or squash, right where the flower meets the stem.

No baby bump, no female yet. Wait.

How long depends on your zone and your planting date. Zucchini from a seed planted after the last frost typically starts flowering around six to eight weeks later. If you set out transplants in a cool May, add time. If you're in the upper Midwest or New England, a cold spring pushes everything back. In the Deep South and the desert Southwest, the problem usually flips, which is the next section.

Not sure of your zone? Your Hardiness Zone Decides What Lives and What Dies will sort that out in five minutes.

Heat shuts the whole operation down

Squash pollen is picky. Once daytime highs sit in the mid-90s and nights stay warm, pollen gets weak and sticky, and female flowers can drop off without ever being fertilized. The plant isn't dying. It's pausing.

This hits hardest in Texas, Arizona, Georgia and anywhere else with a brutal July. A gardener in Phoenix can watch zucchini set beautifully in April and produce nothing in June.

What helps:

• Water deeply in the morning. A soaker hose or a slow hose at the base. An inch a week is the usual target, more in a heat wave. Wet leaves in the evening invite mildew.
• Mulch two to three inches of straw or shredded leaves to keep roots cooler. A bale of straw runs around ten dollars and covers a lot of ground.
• Throw shade cloth over the plants during the worst weeks. Thirty percent shade cloth is cheap and keeps the afternoon from scorching leaves and flowers.
• Plan a second planting. In hot zones, sow again in mid-to-late summer so the plants flower as the weather breaks. It's often the only way to get a fall crop.

If it's a heat spell, sit tight. Fruit usually returns when nights cool off.

You fed it too well

A lot of gardeners do this on purpose. The plant looks hungry, so you give it more. The vines get enormous, the leaves turn dark green and glossy, and the flowers are few or all male.

Too much nitrogen builds leaves at the expense of fruit. Lawn fertilizer is the usual culprit, either spread nearby or worked into the bed. If you've just turned a former lawn into a garden, or you're growing in a bed fed with a lot of fresh manure, suspect this first. (If you're still building the bed, Build a 4x8 Raised Bed for Under Two Hundred Dollars lays out what to put in it.)

The fix is to stop feeding nitrogen. Switch to something balanced or lower in the first number, like a 5-10-10, or a handful of bone meal around the drip line. Finished compost is gentle and plenty for squash.

If you want certainty, a soil test through your county extension office is typically somewhere in the range of fifteen to thirty dollars depending on the state. You'll know what you have instead of guessing. It's the cheapest insurance in the garden.

Nothing is visiting the flowers

Squash flowers open at dawn and are usually done by late morning. One day, one shot. Bees do the work, and squash bees in particular are up early. If your yard has few bees, or the flowers open on a cloudy, rainy morning, pollination doesn't happen.

Common ways gardeners cause it themselves:

• Row covers left on too long. They protect young plants from cold and pests. Pull them the day female flowers show, or the bees can't get in.
• Spraying at the wrong time. Insecticide in the morning hits bees at work. If you must spray, do it after dark and read the label.
• Planting one lonely plant in the middle of a lawn with no other blooms around. A few zinnias, borage or marigolds nearby give pollinators a reason to stay.

I wrote more about what happens when the fruit starts and then rots in Your Zucchini Rots Because Nothing Visited the Flower. Same cause, later symptom.

Pollinate by hand and stop waiting

It takes two minutes and works nearly every time.

1. Go out early, before about 9 a.m. The flowers need to be freshly open.
2. Find a female with a baby fruit at the base, and a male with a straight stem.
3. Pick the male and peel the petals back so the center is exposed. That center is the anther, and it's dusted with yellow pollen.
4. Touch it to the center of the female flower. Dab it around the middle. Use one male per female, or one male for two or three.
5. Or use a small brush. A soft paintbrush or a cotton swab runs about two dollars. Dab the male, then the female.

You'll know it worked within three to four days. A pollinated fruit swells and darkens. An unpollinated one yellows at the tip, shrivels and drops.

If you can't tell which flowers are which, pick a male and a female for a week and compare them. You'll learn it fast.

The slow-burn fixes

If the plant has set fruit before but this year's a bust, check these.

• Crowding. Plants closer than two to three feet fight for light and airflow. Thin them. One or two zucchini plants will feed a family. Four will feed the street.
• Not enough sun. Squash want six to eight hours of direct light. Shade makes for a lot of leaf and little fruit.
• Planting too early. Cold soil stunts roots. Wait until the soil is around 65 to 70 degrees. A ten-dollar soil thermometer takes the guesswork out.
• Old seed. Squash seed lasts a few years at best. A new packet costs three or four dollars.

When it finally goes

Once the females start, you'll have more than you can eat. Pick zucchini small, around six to eight inches, and keep picking. Leave one to get giant and the plant slows production.

Then do what gardeners have always done. Put a bag on a neighbor's porch. Take a few to the guy down the street who's been mowing your side of the fence line. Nobody has ever been annoyed to get fresh zucchini, though by August they may quietly lock their cars.