Fruit trees propagated from seed sometimes do not bear fruit with the same qualities as that of the mother plant. This is due to cross-pollination; the insect that pollinated the flower had transferred pollen from the flower of another tree, producing seeds that either combine the characteristics of both trees, or show the more dominant of the two.

Behind my house is a starfruit tree whose fruit is very sweet and juicy. When a seed sprouted, I let it grow until it bore fruit. These, it turned out, were very sour so I cut the tree down. A neighbour also has a starfruit tree. I have not tasted its fruit but it could be sour, and an insect pollinator could have transferred that sourness to the progeny of my tree.

This is the reason why serious gardeners avoid growing fruit trees from seeds. Apart from taking longer to bear fruit, they may produce fruit that is not true to type, that is, different from the mother tree. If the fruit is better, then it is a boon to the grower, but often they are of inferior quality.

HANDS-ON: Above, from top, to divide a fern, remove the plant from its pot and separate it into smaller clumps, then repot the divisions into individual pots.

However, do not write off cross-pollination altogether. Hybridisers intentionally cross plants to combine the best characteristics of the two. For example, if the neighbour's sour starfruit is more resistant to pests and diseases, hybridisers could cross it with my starfruit to produce a sturdy tree with sweet fruit. Thai hybridisers have used the process to produce the best durian, santol, rose apple and the myriad other fruits that we now enjoy. Selecting the right combination, however, takes many years.

If the intention is not to develop a new cultivar but just to improve the quality of a tree's fruit, grafting is used. By taking a stem of a sweet variety and implanting it on the trunk of a pest-resistant sour variety, you will have a sturdy tree with sweet fruit. Many of the saplings sold by nurseries are propagated this way.

I did not know that, like fruit trees, ferns grown from spores are sometimes different from the mother plant until nursery owner Noppadon Na-ngern told me during my visit to his plant nursery in Ang Thong recently. However, unlike cross-pollinated trees whose fruit are sometimes inferior, some of the ferns he developed from spores are mutants that are highly prized by collectors.

To produce ferns that are exact replicas of the mother plant, he propagates it by plant division. Perennials that form a dense clump, such as the ferns in the genus Nephrolepis (Boston, fishtail and sword ferns), sansevieria (also known as mother-in-law's tongue), spathiphyllum (known in Thai as daylee), asparagus (prig hang karok); or produce miniature plantlets around the mother plant, such as agaves and aloes; or form offsets or pups, such as bromeliads, can be easily divided.

Plant division is the easiest way of propagating plants. Whether you are dividing a clump of fern, a spathiphyllum or any other plant which has outgrown its pot, the method is the same. First, you have to remove the plant from its pot. Don't tug on the stem or foliage as this may damage the plant. Instead, spread the fingers of one hand between the foliage and over the rim of the pot, then with your other hand turn the pot upside down. Insert a forefinger into the drainage hole at the bottom of the pot and push the plant out, or use a pencil or a stick if the drainage hole is too small for your finger.

If the plant does not slide out readily or if the pot is too large to turn upside down, lay it on its side and tap it all around, or slide an old table knife around the inside of the pot, to loosen the soil. Once the plant is out of the pot, shake the loose soil from its roots. Tease the roots apart with your fingers to separate the individual plants, or, if the roots have formed a dense mass, use a sharp pair of scissors to make clean, decisive cuts through the root ball.

Make sure to retain a good chunk of roots for each clump of leaves, and work quickly to prevent the roots from being exposed to the air for too long. If you are interrupted before you can repot the divisions, cover the roots with a damp cloth or newspaper to keep them from drying out.

Different plants call for different soil mixtures. For ferns and bromeliads I use chopped coconut husk, the coarseness of which depends on the size of the plant. Small plants call for finely chopped material. For his ferns, Mr Noppadon uses a mixture of finely shredded and coarsely chopped coconut husk.

After you have divided your plant, fill about one-third of the pot with the planting medium, put the plant in the middle and fill the space around it, making sure that the soil level is the same as it was in the original container. Once all divisions have been planted in their new pots, spread a spoonful of slow-release fertiliser around each plant then water them thoroughly.

Email nthongtham@gmail.com.