Hand Pollinating Zucchini and What to Do When There Are No Male Flowers

When hand pollination is actually needed

Zucchini has separate male and female flowers, and if insects move the pollen you do not need to do anything. The problem is that a female flower is only open from early morning for a few hours. If nothing visits in that time, the fruit yellows at a couple of inches and drops.

In a home garden with few plants, the chance of a male and a female opening on the same day is low, so left alone the fruit sets in fits and starts. On the days below, do it by hand.

1. Overcast and wet days Wet pollen does not fertilize, and bees do not fly. Pick a male flower the day before rain, keep it under cover, and use it the next morning.
2. Early in the season While the plant is small few flowers open, so you cannot rely on chance. Pollinate the first three or four fruit by hand every time.
3. In a town garden or on a balcony There are simply fewer pollinating insects. With one plant you cannot even source a male flower, so plant at least two together.

Telling male and female flowers apart

You can tell at a glance from the base of the flower. A female has a small fruit behind it before it opens, a male has only a thin stalk. Both last a single day, and yesterday's collapsed flower is no use.

1. Female flowers There is already a young fruit an inch or two long behind the flower. The stigma in the center is divided into three lobes with a moist sheen.
2. Male flowers A thin stalk behind the flower and a single stamen dusted with yellow pollen in the middle. They are more common on the outer nodes.
3. Flowers open today The petals are held wide and dry inside. Yesterday's flower is limp and half closed and the pollen is damp and will not shed.

A fruit behind a flower that is already thin and shriveled at the tip was never fertilized. Do not pollinate it, pick it off.

Pollinate before mid morning on the day it opens

The stigma is receptive right after the flower opens, and the set rate drops as the morning goes on. Finish by ten in the morning, and preferably by nine. Once it warms up the pollen itself deteriorates.

1. Pick a male flower Take a male that opened today, with its stalk. One male carries enough pollen for two or three females, but if in doubt use one per female.
2. Strip the petals Pull the petals back so the stamen is exposed. Petals in the way stop the pollen reaching the stigma, which is how you pollinate without actually pollinating.
3. Brush the stigma Touch the stamen lightly around the stigma. Do not press: bruising the stigma does damage, and pollen transferring at all is enough.
4. Note the date Write down the day you pollinated. The picking window is only four to seven days from flowering, so knowing the date is what stops you picking late.

When there are no male flowers

Early in the season it is common for females to open before the males catch up. Cool weather and too much fertilizer both skew it that way, and it corrects itself as the plant grows and the weather warms.

In high summer the reverse happens: heat stops the females and you get only males. Both are temporary, so there is no need to pull the plant, but write off the fruit for that period and manage to keep the plant healthy.

1. Borrow from elsewhere A male flower from a pumpkin or another squash works. Different species in the same family still set a normal, good tasting fruit.
2. Pick a bud the evening before Take a male bud that looks ready to open, keep it indoors dry overnight and it opens in the morning. Useful insurance when rain is forecast.
3. Remove the first fruit or two Fruit on a small plant never fills and just costs the plant. Pinch the buds out and put the energy into growing the plant instead.
4. Let it rest in extreme heat Above 95F (35C) for days on end the pollen quality drops. Do not force it: feed and water to hold the plant, and start again when it cools.

Fruit that does not fill, or narrows at the tip

An unfertilised fruit yellows from the stalk end, stops at about four inches and drops. A fruit that thins only at the far end is either partly pollinated or short of food, and because it looks half grown it is the easier one to misread.

Carry no more than two or three fruit at once on a plant. Hanging on to extra small fruit means none of them fill evenly.

Reducing how often you need to do it

If you want fewer mornings spent pollinating, change the planting rather than the routine. Growing flowers with a long season near the zucchini brings pollinators in and keeps them there, and the number of mornings you have to intervene falls noticeably.