Although cacti are spiny, they are loved for these very spines. But when a cactus starts losing its spines, the gardener may become worried. Let’s see why a cactus can lose or break its spines and if these spines can grow again.
What are Cactus Spines?
Most cacti don’t have true leaves or branches. Instead, they have areoles, highly modified branches, in the form of tiny bumps that spines grow from. Areoles sit on enlarged bases known as tubercules. Cactus spines are actually modified leaves. Young spines contain living tissue that develops from cluster of cells known as spine primordia. But this tissue then dies back to form a mature and hardened spine.
Spines are of various shapes and sizes. They may be thin or thick, feathery or hairy, straight or twisted, round or flat, needle-like or awl-like, or flattened or ridged. They also come in a wide range of colors, depending on the variety of cactus. Glochid is an example of cactus spine. This is a small, barbed spine that commonly occurs on the prickly pear cactus.
But why does a cactus shed its photosynthesizing leaves and develop spiny protrusions? The reason is that cacti can photosynthesize with their stem. They don’t need leaves the way other plants do. Besides, they usually grow in places where there is plenty of sunlight.
Spines are a great help to cacti in the desert environment. They trap air, collect water and keep predators away. If a cactus loses spines, it won’t look as decorative and might even die, depending on the cause.
Some cacti without spines may have been damaged in the area of areoles or spine cushions, whereas in other cases, spines are purposefully removed from cactus plants. Accidents happen too and the spines may get knocked off the plant. One may wonder if the spines will regrow. There are many other reasons too (given below).
The good news is that, yes, the plants may grow new spines only from the living spine primordia of new areoles that develop on the stem as the cactus grows. One just can’t expect them to regrow at the same spot.
Reasons of Losing Spines
Pests are one of the main reasons why your cactus is losing spines. The most common pest that causes the loss of spines is mealybug.
Mealybugs are white and look like cottony substances. If they invade your cactus, they’ll be seen on various parts of your cactus. But if no white fluff is seen anywhere on the stem, allow your cactus to dry out and then remove it from the pot.
Then check its roots. If you find white residue on roots, it could be mealybug invasion. These pests suck out the sap and cause loss of spines. If left untreated, they’ll kill the cactus eventually.
Another pest that usually hides in the cactus roots is nematode. Since they remain hidden, most gardeners don’t find them early. Also, they’re too small to notice, hence you’ll have to look for other symptoms which include loss of spines of course, loss of cactus coloration and swollen roots.
If your cactus has been previously infested by another kind of pest, the affected spots may lose spines which can heal, but won’t regrow if damage is extensive.
Lack of Nutrients
Your cactus may lose spines even when it lacks in nutrients. This can become serious, for example, if you haven’t repotted your cactus for over 2-3 years and haven’t fertilized it.
Lack of potassium, particularly can cause loss of spines on cacti. This is the reason why lower nitrogen and higher potash fertilizers are recommended for cacti.
Cacti do well if fertilized during the growth period. There are many types of fertilizers available. Most of them are liquid ones. You have to dilute them and use a few times during the summer. Slow-release fertilizers are also excellent for cacti and keep feeding them for months.
Overwatering is a big problem with cacti and can sometimes cause loss of spines. If you place your cactus in a sunny spot with warm temperatures, it will require more water. This is particularly true during growth period. However, you should make sure your cactus dries out before you water it again. Make sure to use containers with drainage holes only.
Cactus owners living in areas with cold winters make a common mistake of not letting their cacti go through dormancy period during winter.
If temperatures in your area get low with scanty sunlight, you should place your cactus in a cool spot with temperatures around 55–59-degree F (13-15 degree C). Water it lightly once in 4-6 weeks. Make sure the soil dries out before watering every time.
Keeping your cactus indoors, particularly by radiators together with reducing or stopping irrigation altogether will cause your cactus to start forming thin and elongated growth and loss of roots.
But even keeping it indoors and watering too often might cause overwatering, because of lack of sunlight. This in turn results in loss of spines.
With larger cacti that grow outdoors in hot climates, underwatering can also be a problem. Shrinking of a cactus is a symptom of underwatering. Plump stem and leaves is a sign of sufficient water stored in the cactus.
Lack of Sunlight
A less common reason of loss of spines in cacti is lack of sunlight. This generally happens when your cactus belongs to a jungle/desert area and you live in a colder climate.
Most cacti need bright sunlight, some needing a shade during the hot summer afternoons and evenings. Even tropical cacti need bight but filtered light. If your cactus doesn’t get adequate sunlight for a prolonged period of time, it won’t grow and may start losing its spines.
Turning Your Cactus too Frequently
Cacti don’t like to be turned too frequently, particularly when they prepare to bloom. If you notice your indoor cactus is leaning, you should turn it so that its other side faces the sun. However, if it’s preparing to flower, don’t turn it around, as this will disturb its blooming process and may even cause loss of spines.
If your cactus is rotting, its spines may fall off. Cacti can suffer from dry and wet rot resulted from bacteria and fungi.
In case of a wet rot, your cactus will start appearing soft and mushy, whereas if it’s a dry rot, the cactus will turn brown and start corking usually from bottom to top of the stem.
Check your cactus by squeezing it a bit – if there’s any resistance, it’s a good sign. Also examine its roots to see if there’s anything unusual. If there is, replace the soil, disinfect shears/scissors and cut off the unusual parts of roots or cactus. Wait for a week before watering and putting it out in the sun.
Physical damage is another common cause of loss of spines in cactus. Pets can cause this damage or cacti placed outdoors can be damaged by small animals. Spines on cacti can get easily detached with physical contact, particularly when in contact with fur.
Some sellers sell cacti with fake flowers glued or pinned to them. The cactus gets damaged at the spot where hot glue or pin is applied. In such a case, you should try to remove the flowers or let them come off over time. The damaged spot won’t regrow the spines but will eventually heal.
What to Do if the Cactus Loses Its Spines
You can find the reason from those given above why your cactus is losing spines and do the needful accordingly.
Since spines are an essential part of the body of the cactus plant, it won’t fail to make every effort to repair the damaged stems.
As long as it’s showing overall continued growth and health, new areoles will form and new spines will develop. You just have to be patient. Some cacti tend to grow slowly and may take a while for growth and formation of new areoles.
However, you can speed up the growth a little by fertilization and placing the plant in full morning sunlight. Cactus and succulent fertilizer works well if applied on a monthly or even weekly basis.
If you cannot place your cactus in full sun, adjust it slowly to more daily light. The right light will promote growth of the plant and may help in formation of new spines.
So, are you now relaxed and confident that even if your cactus is losing spines, it can be healthy and spiny again?