Q I have a healthy and fruitful “Royal” medlar (Mespilus germanica). When can I pick its fruits? They are full size by October, but they stay too hard for eating. Any suggestions?

— Mariella Potter, San Gabriel Valley

A The medlar is indigenous to the same part of the world as almond, walnut, pistachio, plum, cherry, fig, quince, pomegranate, grape and pear. This area is Southwest Asia, home to more orchard fruit and nut species than any other place on Earth.

Most of these species can survive on a minimum of precipitation, something to take into account when growing them in our own backyards.

The medlar is a large deciduous shrub or small tree but has a lower chilling requirement than peaches or apricots. When it comes to deciduous fruit trees, chilling requirement refers to the number of winter hours below 45 degrees that are required to open flower buds and set fruit the following spring.

Since sweet cherries, for example, have a high chilling requirement, you cannot grow cherries in Los Angeles since the winters here are just not that cold. With medlars it’s different. They have a low chilling requirement and may be grown locally.

Medlars are among the most misunderstood fruits since they need to begin to rot in order to be appreciated. They resemble “Hachiya” persimmons, which also ripen in the fall, in this respect. (“Hachiya” persimmons, cut in half and eaten out of the skin like custard once they soften up, are elongated fruits, whereas “Fuyu,” the squat persimmon variety, is generally eaten when pulp is still crisp.)

Medlars are harvested in late October and beyond, staying on the tree into winter, but they may take several weeks to ripen or blet, a word that refers to the pulp softening process, after they are picked.

Once the pulp blets — that is, after it turns brown, begins to ferment, and has a mush-like consistency — it is ready to eat. Scoop it out with a spoon. Flavor is somewhere between apple sauce and dates with a sprinkling of cinnamon.

In cold climates, the first frost will start the bletting process in medlars, but in warm climates like Southern California, picking is required to accelerate bletting.

Here it is pertinent to mention that, when you grow your own produce, knowing when to harvest is important to enhance the flavor of your crops. Fruits are divided into two groups, depending on whether they are generally harvested in a ripe or unripe condition. Those fruits that are harvested unripe produce ethylene gas, a plant ripening hormone, after being picked and get sweeter each day following harvest.

Ethylene hastens the ripening process and, for this reason, it is recommended that, if you want to accelerate ripening, fruits harvested when they are unripe — such as avocados, bananas, and pears — should be placed in a paper bag after being picked or when you bring them home from the market and they are still hard or green.

The ethylene released by these fruits, when they are trapped in a closed paper bag, will speed up the ripening process. Do not put these fruits in plastic bags, however, since paper bags allow for gas exchange with the outside air, keeping fruit relatively dry and pathogenic fungi at bay.

You can hasten the ripening of your fruit even more by placing two different ethylene producers, such as an avocado and a banana, in the same bag since each will benefit from the ethylene released by the other.

Ethylene producing fruits also include apples, apricot, cantaloupe, kiwi, mango, papaya, peach, nectarine, plum, passion fruit, guava and tomato. All of these fruits, once they are picked, continue to ripen and sweeten.

By contrast, other fruits stop sweetening and ripening the moment they are picked, so if they are picked tart, they will remain that way. They may eventually soften, but this is a sign of deterioration, not ripening.

Fruits in this category include every kind of citrus, grapes, strawberries, blueberries, pineapple, watermelon and cucumber.

An aside: yes, tomatoes and cucumbers are fruits and, moreover, if your kids won’t eat their vegetables, tell them that there really is no such thing. Bell peppers, chili peppers and eggplants are also fruits. Lettuce and cabbage are leaves; radishes, carrots and beets are roots; beans are pods; peas and corn are seeds; broccoli heads, cauliflower, and artichoke are flower buds, and Brussel sprouts are leaf buds. No, there is no such thing as a vegetable.

Getting back to medlar trees, they make fine ornamental subjects, too. In the manner of persimmons, their leaves change color in the fall, showing off brilliant fiery colors. They put on a white flower show in the spring and their mature fruits are a pleasant burnt orange to russet, around 2 inches in diameter, resembling oversized rose hips.

This is not a coincidence since medlars — like apple, pear and quince — belong to the rose family. You can order medlar trees by mail order from two Pacific Northwest nurseries through these websites: raintreenursery.com and onegreenworld.com.

Q A lot of us have a small fortune invested in cacti and succulents that are both potted and planted. Please tell us how we can protect them from El Niño if it ever shows up. I’m especially interested in how to protect the ones in pots. They’re numerous and many are too heavy to move. In years past I’ve tried covering them in plastic, but that doesn’t work too well. For the ones in the ground, I’m just going to cross my fingers and hope they don’t drown.

—Sandy Sand, West Hills

A As for containers, your best bet is to cover them when rain is forecast. You can do this with a cold frame (wood-framed box with glass or plastic sides) or even a strong cardboard box.

You should be able to collect cardboard boxes for free by visiting the produce department of any supermarket. Cover the boxes with plastic so they stay dry when it rains.

If you have lots of plants — whether in containers or the ground — you could cover them with plastic sheeting or tarps.

I think that rain exclusion is probably the safest way to go. Just make sure you take the plastic off when the rain stops, although if freezing weather is forecast, keep the plastic on.

For more information about area plants and gardens, go to Joshua Siskin’s website at www.thesmartergardener.com. Send questions and photos to Joshua@perfectplants.com.