How do you grow Adenium obesum (desert rose) seeds, why do the leaves turn yellow, and when should you sow them?

Adenium obesum, also known as the desert rose, loves a hot, dry environment with plenty of sunlight, tolerates intense heat but not cold, and is extremely beautiful when in full bloom, so it is often grown as an ornamental. People love to keep it as a potted plant, so do you know the methods for growing desert rose from seed? Why do the leaves turn yellow? When should you sow? According to encyclopedic sources, desert rose is best sown in summer, with a germination temperature of 21°C. Roots form in about 25 days, and after 45 days it can be cut and potted up.

Methods for growing desert rose from seed

1. Planting

The desert rose is native to dry desert regions and can withstand scorching weather. When the temperature is too low or water is lacking, the desert rose will drop its leaves and go dormant. Proper pruning can encourage branching and flowering; when the branches of the desert rose grow longer than 30 cm, they can be pruned, usually once every two years. The desert rose needs ample sunlight; insufficient sunlight will make the plant grow leggy, thin, weak and prone to disease, and it will be reluctant to flower. However, seedlings or plants that have just been repotted should not be exposed to blazing sun, and at midday in the dry, scorching heat of summer they need a little shade (25-30% shading). The flowering temperature for the desert rose is 20-35°C, and in tropical regions it can flower all year round. The optimum temperature for growth is 22°C-30°C; above 38°C it stops flowering, and it can withstand high temperatures of 40°C. Below 12°C it enters dormancy, and the wintering temperature is 10°C.

2. Propagation

The desert rose can be propagated by cuttings, sowing, rootstock grafting or air-layering of branches. The most suitable time for sowing is spring, when growth will also be faster; summer and autumn are also fine, but sowing in winter and the rainy season should be avoided. After the seeds are harvested, they should be sown as soon as possible to keep them fresh; if they cannot be sown within a short time, they should be sealed well and stored in the refrigerator, then taken out when it is time to sow. The longer the seeds are kept, the lower the germination rate, and it is best not to store them in the refrigerator for more than 3 months. [2]

As for the air-layering method, it is best carried out on warm, humid days from spring to summer. Because the sap of the desert rose is toxic, you should wear rubber gloves when doing this and avoid letting the sap touch your eyes and mouth. First select a mature, robust branch, and use a sterilized knife to cut a ring all the way around the branch at the spot where you intend to break it off later; the cut must go through the bark to the woody layer, but the branch must not be cut through. About two centimeters away, make another ring cut in the same way. Between the two rings, make another straight cut, also through the bark to the woody layer, as an opening, and peel off the bark layer between the two rings until the woody layer is exposed. If the bark layer is not completely peeled off, it will affect root formation. Then let the wound air-dry for a day. Once the wound is dry, soak sphagnum moss thoroughly in clean water, then squeeze out the excess water and set it aside. Cut open a transparent plastic bag, sized so that it can wrap the peeled part and the sphagnum moss. Use thin string to tie one end of the plastic bag about one to two centimeters below the first cut, then wrap the wound with the sphagnum moss, covering the wound completely. Then, about one to two centimeters above the second cut, tie the other end of the plastic bag securely with thin string; the plastic bag must not be left open, to prevent moisture loss. Usually after twenty to thirty days, the cut area will begin to form roots. If during this period you find the sphagnum moss dry, you can untie the string at the top end, inject an appropriate amount of water at the opening, and tie it up again, but do not water too much; the standard is that there is no standing water at the bottom of the plastic bag. After roughly another thirty to fifty days, you will see new roots growing; at this point you can remove the plastic bag and sphagnum moss, cut off the rooted branch and transplant it. When transplanting, first spread crushed stone or clay pebbles at the bottom of the pot as a drainage layer, then add about one third soil on top, then spread the roots that have grown out as widely as possible in all directions inside the pot, add the rest of the soil, and place it in a bright spot; wait three to seven days for the wound to heal before watering. The position should avoid the strong sunlight of high summer, or shade netting should be added at midday in high summer; the potting soil should not be allowed to get too dry, and no fertilizer should be applied until the young plant begins to produce new leaves, after which normal care can be resumed.

3. Watering

The desert rose prefers a relatively dry environment, so it must not be watered too much; leaving it too wet for a long time will cause water to accumulate in the potting soil, leading to root rot, and will also make the branches prone to leggy growth, ruining its original ornamental value.

Watering should be considered comprehensively according to different weather conditions and the growing medium and other factors. Generally, in spring and autumn water about once every 3 days; in summer water more often, once every 1-2 days; in winter water less, once a week is enough.

4. Fertilizing

During the growing season, the desert rose should be given more phosphorus and potassium fertilizer and less nitrogen fertilizer, because nitrogen fertilizer can cause leggy growth of branches and leaves and inhibit the plant's growth. When the plant enters the growth and reproduction period, phosphorus and potassium fertilizer should be the mainstay and nitrogen fertilizer should be stopped.

Generally, fertilizing stops during the flowering period. The desert rose flowers for a long time, so it consumes a great deal of its own nutrients; a small amount of quick-acting fertilizer can be added as a supplement, but the concentration should not be too high. During vigorous growth, fertilize once every 2-3 weeks; fertilizing must be stopped during the winter dormant period.

5. Light

The desert rose is suited to growing in a warm, sunny, well-lit environment and generally does not need shading; the desert rose can be placed in a spot with ample light for care. However, summer sunlight in the south is relatively intense, so pay attention to observing the leaves and take careful care, and it can be shaded appropriately.

Why do desert rose leaves turn yellow?

Environmental changes

We often class the desert rose as a succulent plant; its stem is relatively large and it can survive in arid environments. The desert rose does not tolerate damp environments, so if it is watered too much, or left out in too much rain during the rainy season, and on top of that the air cannot circulate and the light is weak, the desert rose will develop yellow leaves, and in serious cases the whole desert rose plant will rot and die.

Solution

In daily care we need to understand its growth habits and care for it reasonably according to its condition to prevent this from happening.

Overwatering

Overwatering is also an important cause of yellow leaves. The desert rose does not tolerate dampness, so the amount of water given must not be too much; otherwise it will cause water to accumulate at the roots, leading to root rot, which makes the leaves turn yellow and drop, and even wither.

Solution

Cut away the rotted roots, and pay attention to watering the desert rose reasonably; do not give too much water. Water sparingly; the desert rose is drought-tolerant, so it does not need much water.

Fertilizing at low temperatures

In winter the climate is cold and the temperature is low; at this time the desert rose enters dormancy, and it will dry out and drop its leaves in order to reduce its own water evaporation and protect itself. At this time fertilizer must not be applied too much or too concentrated, otherwise it will cause the leaves to turn yellow or even die.

Solution

Keep the temperature suitable and the amount of fertilizer reasonable, not too much; it is best to place the desert rose in a greenhouse for cultivation.

Poor ventilation

The desert rose likes warmth and a well-ventilated growing environment; poor ventilation will cause the plant's roots to rot and its leaves to turn yellow.

Solution

Place the potted desert rose in a ventilated spot indoors, such as a balcony or windowsill, for growing.

Pests and diseases

Pests and diseases are also an important cause of yellow leaves in the desert rose. Its main pest is scale insects; when the infestation is severe, it can cause the whole plant to drop its leaves, stop growing, and eventually die.

Solution

If scale insects are found, promptly use a 40% omethoate emulsifiable concentrate solution diluted 2000 times for spraying and control.