Pollination, optimal conditions needed to produce pistachios

QI have a pistachio tree and lots of pistachios ( grow) on the tree, but when I open the shells there is nothing inside, just a tiny bit of seed. I don’t know what’s going on. Can you please advise what’s going on with my tree?

— Ajit ChAmpAneriA,

SAn Jose

AWhat you are seeing is what the pistachio industry calls “blanks.” It’s an indication that the tree wasn’t pollinated.

Many trees, including pistachios, require both a male and a female tree to make a connection in the spring, thereby producing nuts. If you never get any pistachios, you probably don’t have both sexes of trees. If you’ve had nuts before, then there could be a few reasons why it didn’t work this year.

Fruit and nut trees all require a certain number of “chill” hours in the winter in order to produce. If the winter is too mild, the trees don’t get enough of those temperatures. Drought and high heat also can take a toll on productivity, causing the male trees to misfire and release their pollen before the female tree is ready to receive it.

In instances when weather or climate conditions intercede, there’s nothing you can do to change it. Pistachios are wind pollinated, so you don’t have to grow both, as long as a male tree is relatively close by. But if the male tree that has been pollinating your tree has died or was removed, you should look at getting another one. If space is an issue, you can graft a male branch onto the tree.

QWhy do I get white spots on my mint, planted in a good sized pot located on my porch?

I have had a pear tree in my yard for many years with very sweet pears, but over the last two years, the black walnut tree has cross-pollinated with it and the fruit is altered and not the same. It looks like hybrid fruit.

The trees are 1,520 feet part. My walnut tree is trimmed this year, and has been regularly in the past. How do I stop this cross-pollination?

— DushyAnt, BAy AreA

AHerbs typically don’t have too many diseases or insect problems, but it could be spider mites. They are so tiny that you usually notice the damage first before you see the insects.

Spray the mint with an insecticidal soap or with a hard stream of water from the hose. Be sure to get under the leaves and repeat as needed.

As for your pears, I’m not certain what’s going on there, but it’s not cross-pollination from your walnut tree. Fruit and nuts tree don’t pollinate with each other.

If your pears are misshapen, the tree likely has an insect problem, a fungal disease or an issue with proper watering.

If the pears look fine by don’t taste as good, it could be weather related — too warm in the winter or too hot in the summer. It could also be a watering issue. It’s time to check your growing procedures and watering schedules to make sure you’ve got everything correct.

Harvesting pears at the wrong time can also change the flavor. Pears ripen from the inside out, so over-ripe pears can be mushy and tasteless and have a gritty feel in the mouth. Pears are one of those fruits that shouldn’t be left on the tree to ripen. They are best when picked while they are still a bit hard,\ and then placed in cold storage — or the best we can do — to finish ripening.

The tree also might benefit from a second pear tree planted nearby. Make sure the varieties are compatible. The pear doesn’t produce much nectar, so attracting bees is harder than with other fruit trees. Having a second pear tree doubles the chances, and even self-pollinating varieties can benefit from having a pollination buddy.