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.
Source: Nine Homilies of Hexaemeron (New Advent)