Yucca are succulent herbaceous plants from warm and dry environments of North and Central America. They belong to the Agavaceae family and their genus includes no less than fifty species.
There are more or less rustic ones. The former can be grown almost anywhere in our country. The others, on the other hand, must be kept in pots or reserved for the southern regions and coastal areas.
Genus of about 40 species of evergreen trees and shrubs, originating in the southern United States, Mexico and South America; some are without stems, others have erect, vigorous stems, sometimes with some branching, which develop with age. The species grown in the apartment have a woody, erect, poorly branched trunk with smooth bark; at the apex of the stems a thick head of long, fleshy, stiff, pointed leaves of green color is produced; there are varieties with variegated foliage. In the summer occasionally the adult plants produce high panicles, which carry numerous bell-shaped flowers, of white or cream color.
In the spontaneous state, the yucca it is pollinated by the small moth Pronuba, which lays its eggs in the ovary of the flower, pollinating it. Although the larvae feed on the seeds that sprout, they still remain in sufficient numbers for reproduction.
Cultivated varieties: Yucca aloifolia, Y.a. draconis, Y. brevifolia, Y.b. brevifolia, Y.b. herbertii, Y. elata, Y. elephantipes (Y. gigantea, Y. Guatemalensis), Y.e. variegated, Y.Cespitosa, Y.f variegata, Y. flaccida, Y. filamentous, Y. glauca, Y. gloriosa, Y. recurvifolia, Y. whipplei (Hesperoyucca whipplei), Y.w. caespitosa, Y.w. intermediate.
Characteristics of the yucca
The various species can have very different shapes and forms from one another: we go from small shrubs to medium-sized trees. In general we can say that they are characterized by persistent and rigid foliage, with a smooth edge, almost always bearing a spine on the tip. The height at maturity can range from about 60 cm up to more than 10 meters, without counting the floral scape that often exceeds the height of the leaves by many meters: it emerges from the center of the rosette and bears at the top a large number of bellflower-shaped flowers, white, cream or, more rarely, purple.
It is a very suitable to be used as an isolated specimen, but is also suitable for the formation of hedges or as an example from an apartment or terrace, if inserted in large vases.
In the countries of origin it is also used for many practical purposes. From the leaves and roots i can derive a good taste of natural origin. The leaves and trunks are used in the construction of houses. Let us not forget that, in the areas where it is endemic, it produces very attractive fruits: it is very rare for us to see them because the flowers need pollination from insects not present on our continent. The only exception is represented by the Yucca aloifolia: to taste them you must wait until they are well dried on the plant. They have a very special taste of liquorice.
THE YUCCA IN BRIEF
|Height / width at maturity||More than 10 m / up to 4 m|
|Rusticitа||From very to little rustic|
|Soil||Sandy, calcareous, stony. Well drained|
|Soil moisture||Well drained|
Exposure: the yucca are grown in a bright place, possibly away from direct sources of heat and direct sunlight; generally they adapt without problems even in non-ideal cultivation conditions. Although they are mainly cultivated in apartments, some species can easily tolerate frost, so they can find a place in the garden. They prefer fairly cool temperatures, so in summer it is advisable to place them in a semi-shady, well-ventilated place; during the winter months we remember to re-vaporize the foliage frequently with demineralized water.
Watering: during the vegetative season the Yucca, from March to October, water abundantly, always waiting for the soil to dry well between one watering and another. When the temperatures go down, reduce the watering; in winter it is sporadically watered. In the vegetative period, provide specific fertilizer for green plants, every 15-20 days, mixed with the water used for watering.
Soil: cultivate in balanced universal soil; to improve drainage we add to the soil a good quantity of sand or lapillus. In general, these plants do not develop a conspicuous root system, but we remember to repot them every 3-4 years.
Multiplication: it takes place by sowing, in February-March at a depth of 0.5 cm, in a wet and well-mixed mixture, formed by 2 parts of the compound of cultivation and a part of coarse sand. The plants are placed in a box to be kept in the shade at a temperature of 21 ° C; when the seeds are germinal the seedlings are moved into a luminous position. When the plants are at 5-8 cm, they are transplanted individually.
Pests and diseases
Yucca plants generally fear the cochineal, leaf and root very much, especially in conditions of low humidity. The leaf will show dark spots on the bottom. The quickest remedy is to remove these specks with an alcohol wipe, or rub the leaves gently with a sponge to remove the parasites.
The plant can suffer and become ill also for other causes, for example due to poor lighting, excessive watering or the attack of fungi such as Botrytis. In this specific case, the plant can even die if left untreated. It is therefore good to use specific fungicides and eliminate the parts of the yucca affected.
Many yuccas can be grown in pots. If we live in an area characterized by cold climates it will be the only solution in case we want to grow specimens sensitive to low temperatures. They will only need some more attention, but they will always give great satisfaction.
THE YUCCA CALENDAR
|Flowering||From May to October|
|Pruning||From February to April|
Soil and composition of the vase
The same rules apply as for plants growing in the open ground. However, in the container it is necessary to pay even more attention to the quality of the drainage, creating a thicker layer of gravel on the bottom and adding a few more pebbles to the compote.
Almost all of them are able to withstand very well temperatures up to 5 ° C. Those that are withdrawn at home are good to be kept between 15 ° C and 18 ° C, therefore neither too hot nor too cold. The position in all seasons must always be very bright.
Light and excessive heat can only be a problem during the summer, especially when concentrated by a window pane. In that case it will be good to move the specimen where it is reached by the sun only in the morning or evening.
Outside, on the other hand, it supports temperatures even above 30 ° C.
Irrigation and fertilization
Interventions must be carried out only when it is ascertained that the soil is totally dry even in depth. The ideal is therefore to abundantly water (until the water comes out of the drain holes) and let a long time pass before intervening again, always monitoring the situation of the substrate by inserting a finger deep down.
From spring to autumn, every 15 days, it is useful to administer a liquid fertilizer for green plants, diluted with irrigation water.
Repotting takes place every four years, choosing a container that is slightly larger than the previous one (+2/4 cm in diameter). As the plant grows it will become increasingly important to choose a heavy container: the greater weight will guarantee greater stability to the complex.
Large size can no longer be repotted: the most superficial layer of substrate is removed, replacing it.
To keep the leaves free from dust (and avoid the onset of pests such as the red spider) it is good to periodically pass them a damp cloth. If our apartment (or our balcony) turns out to be very dry during the hot season it is always a good idea to resort to light sprays with rainwater or distilled water.
The basal leaves of the yucca tend to dry out to be replaced by new ones. It is a physiological event: we must wait for the leaf to be completely dry and then tear it from the base with a sharp blow.
Usually their structure is composed of two or three main trunks that should never be touched.
Instead you can intervene on the secondary ones, but always leaving at least three leaves on each one. The best time is always before the vegetative awakening, between February and March.
If a branch has become too large, cut it at the base, covering the area with a good amount of putty.
The flower stems are eliminated when the flowers have withered.
In our continent it is only possible to carry out agamic propagation, since the flowers are not pollinated by insects.
You can try with the trunk or head cutting: we cut with a sharp saw a portion of trunk about 30 cm long (or 15 cm from a lateral branch). Sprinkle with a rooting product and insert it in a very draining compost. The roots develop in 30-60 days and new leaves appear. At that point you can transfer to the final compost.
The simplest method is, however, the removal of basal shoots. They are separated from the mother plant by a sharp and clean knife. The ideal ones are at least 20 cm and with 4 leaves. They are then placed in 12 cm diameter pots with a compost of peat and sand, to be left in the sun for about two months, often vaporizing.
Pests and diseases
The most frequent parasites are cochineals, which attach themselves to the back of the leaves to feed on the sap, but in the apartment and in very dry areas the red spider mite may also appear.
Rather usual, especially with poorly draining substrates and incorrect exposures, is the advent of botrytis that creeps into the plant bearing rot. Prevention is very important and eventually the infected parts must be eliminated. Help can be specific fungicides.
Cultivation in the open ground
The yucca genus includes a large number of different species, some more sensitive to cold, others much less. It is therefore fundamental, if we live in the North or in mountainous areas, to inform us about the characteristics of the specimens that we wanted to plant in the ground.
However, there is a common characteristic: all do not tolerate the mixture of cold and humidity. It is therefore very important both the choice of exposure and the substrate.
To achieve good growth and avoid the onset of rotting you must always position the yucca in full sun. This is even more important for the plants placed in the middle of the North-Central area: the ideal positioning in that case will certainly be in the South or South-East, possibly near a wall where daytime heat can accumulate to be sold during the hours night. Early morning sun will help to dry up the moisture that accumulates on the ground as soon as possible.
The heat and dryness in the open ground are not a problem.
To obtain a rapid development and avoid radical problems, it is important to insert the yucca in a very permeable and draining soil. The ideal is a compote with field soil (not too clay), a bit of sand and a lot of gravel.
However, some varieties (such as glorious or elephantipes) are very tolerant and adapt to almost all substrates.
The best time to do this is spring, so the plant can root and free itself before the cold season arrives.
You have to dig a good wide and create on the bottom a thick draining layer based on fine gravel. Then we insert the sample and the compote, compressing well and making sure that it is well leveled. Let us water abundantly.
Yucca: Variety of yucca
Here are some of the most common varieties in our country:
Y. brevifolia rustic to -12 ° C, avoiding damp. It has branched and disordered trunks with tufts of short leaves. The spines are very sharp. It can reach 9 meters in height
Y. glorious very tolerant of soil and exposure and totally rustic. It can have a single or multiple trunk, dark green straight leaves ending with a thorn. The flowers are white to pink. It can reach 3 meters in height.
Y. desmetiana medium rustic and small (rarely more than 50 cm). It widens however easily and has soft green-blue leaves, purple when young.
Y.elata medium rustic, suitable for arid and sandy areas. The trunk is not unique with a crown of soft leaves and surrounded by filaments. Up to 5 meters high.
Y. elephantipes very suitable for Central-Southern climates (up to -8 ° C), where it adapts to many different climate and soil conditions. It has lance-shaped and sharp leaves and spectacular and fragrant flowering. It can develop more logs, up to 5 meters in height.
Y. filamentous totally rustic, it also bears moisture well. It is often used as a ground cover and has a beautiful cream-colored bell-shaped bloom. Up to 3 meters high.
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