Watering cactus too often can lead to plant death

Several questions were sent to me regarding cactuses. In general, the most common reason for the failure of cactus is watering too often. The second-most common reason for cactus problems is because it was put in a hot, bright location when it should be located in a protected part of the yard. The third reason is that the cactus was damaged during our winter cold temperatures and prefers being planted in a warmer climate.

Be careful when putting cactuses on an automatic water or irrigation timer. They are watered so infrequently that it sometimes makes sense to water these plants manually with a hose rather than automating the task.

When cactuses begin to shrivel, it’s time to water. When they look plump and firm, they don’t need water.

If you’ve got lots of cactuses and you are using an automatic timer, then run that station or valve when they need water, but make sure they have good drainage if you water them automatically without looking at them. A hose, manual timer and sprinkler also make sense for larger desert plants.

Medium-sized and small cactuses should be watered about 12 inches deep. Large desert plants like a saguaro or Joshua tree should be watered 18 inches deep and have water applied to an area underneath them equal to at least half of their height.

Watering a large area under large plants helps keep them stable and keeps them from falling over when the tops get large and heavy. Watering any of these plants too often can cause disease or unsightly growth problems.

Find out the scientific name for your cactus and Google it. Learn where it originated from.

Some cactuses are native to the Southeast or higher elevations in other countries. In these locations, it is cooler, and they will need protection from late afternoon sun in the Mojave Desert.

Cactuses native to our Southwest deserts do not. They can handle hot and dry locations. Learn if your cactus should be planted in a gentler landscape location or can handle the harsh ones.

Some cactuses are tropical or subtropical and get damaged because of our low winter temperatures in the Mojave. Cactuses that can handle low temperatures of 20 degrees or lower probably will not need much winter protection in all but the coldest years. Other cactuses that are less tolerant of these low temperatures might, depending on your landscape microclimate and location in the valley.

Q: This is the second year for my Santa Rosa plum. I attached some garden trowels to some of the main branches to open up the tree to a vase shape. Is this a good idea?

A: If you follow me long enough you know I like to see flowering and fruiting plants without their branches growing at 45 degrees above horizontal. Many types of plum have narrow crotch angles, and their canopy needs to grow more openly.

Branches growing at 45-degree angles produce an optimum balance between growth and flower or fruit production. Branches growing horizontally or downward may flower well but don’t grow fast. Branches growing nearly upright (vertical) grow very rapidly, but they are slow to flower.

The tree intends for this type of growth to give it height. Some trees grow extremely upright (most pears for instance), and the limbs should be spread apart and pruned to outward growth in mid to late spring to slow it down and improve flowering or fruiting.

Plants don’t care if their limbs are spread to 45 degrees by weights or another method. I prefer to use limb spreaders of different lengths: 4, 8, 12 and 18 inches. They are faster, and less adjustment is needed.

You can make them with forked ends out of 1-inch wood lath and even wooden paint stirrers. They should be strong enough to hold branches apart and not break while doing it.

Be careful spreading limbs apart early in the season when they easily split if bent too far. After the new growth in the spring is an inch or two is the perfect time to bend limbs to their proper angle and either hang weights, use limb spreaders and prune to outside growth to open the canopy wider. After one season of growth in this position, they can be removed.

Q: I have 50-pound sacks of 16-16-16 fertilizer in plastic bags. Somehow moisture got in the bags and the granules are wet enough that the fertilizer doesn’t drop through the spreader anymore. I live in a wet climate. What can I do to dry this fertilizer out?

A: All sorts of scenarios are dancing through my head. Dry fertilizers in bags are meant to stay dry. If dry granular fertilizers stay dry, they are never hard to use. Getting wet is the one thing that can ruin a dry fertilizer specifically designed for use in spreaders that rely on some sort of a hopper (where you pour the dry fertilizer) for spreading it.

Drop spreaders rely on specifically sized granules so its settings can be adjusted properly for a precise application rate. They are usually used for applying fertilizers to lawns.

You have lost the drop spreader application option for that fertilizer. Chalk it up to lessons learned and buy a different bag of lawn fertilizer. This time get a true lawn fertilizer like a 21-7-14 and not 16-16-16. The ideal lawn fertilizer contains less phosphorus like 21–7–14 with half of its nitrogen (the first number) available in a slow-release form.

If this fertilizer was not a “Weed N Feed,” use it for other landscape plants as a compost starter or even in a raised vegetable garden. In desert climates, spread the moist fertilizer out and use the sun to dry it.

After drying, the fertilizer will dry into chunks that must be broken small enough to be used. Breaking it apart also creates some powder. You could still use a rotary spreader provided the fertilizer granules are dried and broken small enough to use its hopper or even apply it by hand.

Fertilizers like 16–16–16 are made by mixing two or three fertilizers with similar-sized granules together. The nitrogen granules in this fertilizer are probably the first to dissolve when it becomes moist.

The dissolving of these nitrogen granules glues the other granules together into chunks. Breaking these chunks apart creates a white powder. You can use this powder to make a liquid fertilizer.

Use no more than 1 to 1½ tablespoons of this powder dissolved in each gallon of water. This solution of water and fertilizer can be used to spray the leaves.

This liquid fertilizer also can be poured safely on the soil very close to the plants. The remaining granular fertilizer can be used just like any 16-16-16 fertilizer. It won’t be 16-16-16 anymore, but it will be a fertilizer probably high in phosphorus and potassium.

Don’t throw this bag out. Use the fertilizer in it. It’s just going to take a little bit of work to get into a usable form.

Q: My son gave me a small coconut tree in a pot for Mother’s Day. I waited about two weeks before I planted it in a bigger pot. I’ve put it on the patio that faces west, so it’s hot in that location. How can I help this coconut thrive in the desert?

A: You can’t. This isn’t the tropics. It can handle our heat but not our cold temperatures. It can’t thrive here even if it survives the freezing temperatures of our winter.

The biggest problem it faces, besides surviving the winter, is the cool spring and fall months. Extended periods of cold below 45 degrees causes permanent damage to a coconut palm.

Coconut palm is truly one of the tropical palm trees. You will find coconut palms in Hawaii and southern Florida, but it’s even too cool for coconut palms in Southern California so we seldom see them there.

Bob Morris is a horticulture expert and professor emeritus of the University of Nevada, Las Vegas. Visit his blog at xtremehorticulture.blogspot.com. Send questions to Extremehort@aol.com.