9 But what need is there to continue, when in the same fig tree we have the most opposite flavours, as bitter in the sap as it is sweet in the fruit? And in the vine, is it not as sweet in the grapes as it is astringent in the branches? And what a variety of colour! Look how in a meadow this same water becomes red in one flower, purple in another, blue in this one, white in that. And this diversity of colours, is it to be compared to that of scents? But I perceive that an insatiable curiosity is drawing out my discourse beyond its limits. If I do not stop and recall it to the law of creation, day will fail me while making you see great wisdom in small things.
“Let the earth bring forth the fruit tree yielding fruit.” Immediately the tops of the mountains were covered with foliage: paradises were artfully laid out, and an infinitude of plants embellished the banks of the rivers. Some were for the adornment of man's table; some to nourish animals with their fruits and their leaves; some to provide medicinal help by giving us their sap, their juice, their chips, their bark or their fruit. In a word, the experience of ages, profiting from every chance, has not been able to discover anything useful, which the penetrating foresight of the Creator did not first perceive and call into existence. Therefore, when you see the trees in our gardens, or those of the forest, those which love the water or the land, those which bear flowers, or those which do not flower, I should like to see you recognising grandeur even in small objects, adding incessantly to your admiration of, and redoubling your love for the Creator. Ask yourself why He has made some trees evergreen and others deciduous; why, among the first, some lose their leaves, and others always keep them. Thus the olive and the pine shed their leaves, although they renew them insensibly and never appear to be despoiled of their verdure. The palm tree, on the contrary, from its birth to its death, is always adorned with the same foliage. Think again of the double life of the tamarisk; it is an aquatic plant, and yet it covers the desert. Thus, Jeremiah compares it to the worst of characters— the double character.
10. “Let the earth bring forth.” This short command was in a moment a vast nature, an elaborate system. Swifter than thought it produced the countless qualities of plants. It is this command which, still at this day, is imposed on the earth, and in the course of each year displays all the strength of its power to produce herbs, seeds and trees. Like tops, which after the first impulse, continue their evolutions, turning upon themselves when once fixed in their centre; thus nature, receiving the impulse of this first command, follows without interruption the course of ages, until the consummation of all things. Let us all hasten to attain to it, full of fruit and of good works; and thus, planted in the house of the Lord we shall flourish in the court of our God, in our Lord Jesus Christ, to whom be glory and power for ever and ever. Amen.
Source: Nine Homilies of Hexaemeron (New Advent)