Consider a Tree for a Moment: Tu Bishvat
וַיֹּ֣אמֶר אֱלֹהִ֗ים הִנֵּה֩ נָתַ֨תִּי לָכֶ֜ם אֶת־כָּל־עֵ֣שֶׂב ׀ זֹרֵ֣עַ זֶ֗רַע אֲשֶׁר֙ עַל־פְּנֵ֣י כָל־הָאָ֔רֶץ וְאֶת־כָּל־הָעֵ֛ץ אֲשֶׁר־בּ֥וֹ פְרִי־עֵ֖ץ זֹרֵ֣עַ זָ֑רַע לָכֶ֥ם יִֽהְיֶ֖ה לְאָכְלָֽה׃
God said, “See, I give you every seed-bearing plant that is upon all the earth, and every tree that has seed-bearing fruit; they shall be yours for food.

(א) הִנֵּה נָתַתִּי לָכֶם אֶת כָּל עֵשֶׂב זֹרֵעַ זֶרַע לא הרשה לאדם ולאשתו להמית בריה ולאכול בשר, אך כל ירק עשב יאכלו יחדיו כלם...

(1) "Behold, I have given to you all of the herbs that gives seed:" "He did not permit Adam and his wife to kill a creature and to eat its meat; only every green herb were they all permitted to eat together....

כִּֽי־תָצ֣וּר אֶל־עִיר֩ יָמִ֨ים רַבִּ֜ים לְֽהִלָּחֵ֧ם עָלֶ֣יהָ לְתָפְשָׂ֗הּ לֹֽא־תַשְׁחִ֤ית אֶת־עֵצָהּ֙ לִנְדֹּ֤חַ עָלָיו֙ גַּרְזֶ֔ן כִּ֚י מִמֶּ֣נּוּ תֹאכֵ֔ל וְאֹת֖וֹ לֹ֣א תִכְרֹ֑ת כִּ֤י הָֽאָדָם֙ עֵ֣ץ הַשָּׂדֶ֔ה לָבֹ֥א מִפָּנֶ֖יךָ בַּמָּצֽוֹר׃
When in your war against a city you have to besiege it a long time in order to capture it, you must not destroy its trees, wielding the ax against them. You may eat of them, but you must not cut them down. Are trees of the field human to withdraw before you into the besieged city?
וְכִי־תָבֹ֣אוּ אֶל־הָאָ֗רֶץ וּנְטַעְתֶּם֙ כָּל־עֵ֣ץ מַאֲכָ֔ל וַעֲרַלְתֶּ֥ם עָרְלָת֖וֹ אֶת־פִּרְי֑וֹ שָׁלֹ֣שׁ שָׁנִ֗ים יִהְיֶ֥ה לָכֶ֛ם עֲרֵלִ֖ים לֹ֥א יֵאָכֵֽל׃
When you enter the land and plant any tree for food, you shall regard its fruit as forbidden. Three years it shall be forbidden for you, not to be eaten.

[...]וידוע כי הפרי הבא עד שלש שנים אין בו תועלת ומזיק כאשר יזיק לגוף כל דג שאין לו סנפיר וקשקשת ויזיק לנפש החכמה בשר כל עוף דורס והבהמות הטמאות והמשכיל יבין:

[...]It is well known that fruit which grows on trees less than three years old is harmful and contains no nutrition (just as fish that do not have fins and scales are harmful, and meat from birds of prey and from the non-kosher beasts is detrimental to the intelligence — verbum sat sapienti ).

אַרְבָּעָה רָאשֵׁי שָׁנִים הֵם. בְּאֶחָד בְּנִיסָן רֹאשׁ הַשָּׁנָה לַמְּלָכִים וְלָרְגָלִים. בְּאֶחָד בֶּאֱלוּל רֹאשׁ הַשָּׁנָה לְמַעְשַׂר בְּהֵמָה. רַבִּי אֶלְעָזָר וְרַבִּי שִׁמְעוֹן אוֹמְרִים, בְּאֶחָד בְּתִשְׁרֵי. בְּאֶחָד בְּתִשְׁרֵי רֹאשׁ הַשָּׁנָה לַשָּׁנִים וְלַשְּׁמִטִּין וְלַיּוֹבְלוֹת, לַנְּטִיעָה וְלַיְרָקוֹת. בְּאֶחָד בִּשְׁבָט, רֹאשׁ הַשָּׁנָה לָאִילָן, כְּדִבְרֵי בֵית שַׁמַּאי. בֵּית הִלֵּל אוֹמְרִים, בַּחֲמִשָּׁה עָשָׂר בּוֹ:

There are four New Years: The first of Nissan is the New Year for kings and for festivals.

The first of Elul is the New Year for the tithing of beasts. Rabbi Elazar and Rabbi Shimon say: The first of Tishrei.

The first of Tishrei is the New Year for years, for shemitah, for the Jubilee year, for planting, and for greens.

The first of Shevat is the New Year for trees according to Beth Shammai. Beth Hillel say: the fifteenth of the month.

מה"מ א"ר חייא בר אבא א"ר יוחנן ומטו בה משמיה דר' ינאי אמר קרא (ויקרא יט, כד) ובשנה הרביעית ובשנה החמישית

Rabbi Ḥiyya bar Abba said that Rabbi Yoḥanan said, and some determined that it was stated in the name of Rabbi Yannai: The verse states: “Three years shall it be as prohibited to you; it shall not be eaten. And in the fourth year all its fruit shall be sacred for praise-giving to the Lord. And in the fifth year shall you eat of its fruit, that it may yield to you its increase; I am the Lord your God” (Leviticus 19:23–25).

באחד בשבט ר"ה לאילן: מ"ט אמר רבי אלעזר א"ר אושעיא הואיל ויצאו רוב גשמי שנה ועדיין רוב תקופה מבחוץ
§ The mishna taught: On the first of Shevat is the new year for trees, according to the statement of Beit Shammai. The Gemara asks: What is the reason that the new year for trees was set on this date? Rabbi Elazar said that Rabbi Oshaya said: The reason is since by that time most of the year’s rains have already fallen, and most of the season, i.e., winter, is yet to come, as it continues until the spring equinox, which usually occurs in Nisan.
ת"ר מעשה בר"ע שליקט אתרוג באחד בשבט ונהג בו שני עישורין
The Sages taught in a baraita: There was once an incident involving Rabbi Akiva, who picked an etrog on the first of Shevat and set aside two tithes. This occurred in the second or the fifth year of the Sabbatical cycle. In the second and fifth years one sets aside second tithe, whereas in the third and sixth years one sets aside poor man’s tithe. Rabbi Akiva set aside both second tithe and poor man’s tithe because he was in doubt about the halakha.
אחד כדברי ב"ש ואחד כדברי ב"ה
One tithe was in accordance with the statement of Beit Shammai that the new year for trees is on the first of Shevat, in which case it was already the third or sixth year, when one must set aside poor man’s tithe; and one tithe was in accordance with the statement of Beit Hillel that the new year for trees is on the fifteenth of Shevat, so it was still the second or fifth year, when one must set aside second tithe.
יומא חד הוה אזל באורחא חזייה לההוא גברא דהוה נטע חרובא אמר ליה האי עד כמה שנין טעין אמר ליה עד שבעין שנין אמר ליה פשיטא לך דחיית שבעין שנין אמר ליה האי [גברא] עלמא בחרובא אשכחתיה כי היכי דשתלי לי אבהתי שתלי נמי לבראי

One day, he (Honi) was walking along the road when he saw a certain man planting a carob tree. Ḥoni said to him: This tree, after how many years will it bear fruit? The man said to him: It will not produce fruit until seventy years have passed. Ḥoni said to him: Is it obvious to you that you will live seventy years, that you expect to benefit from this tree? He said to him: That man (i.e. himself) found a world full of carob trees. Just as my ancestors planted for me, I too am planting for my descendants.

רַבִּי אֶלְעָזָר אִישׁ בַּרְתּוֹתָא אוֹמֵר, תֶּן לוֹ מִשֶּׁלּוֹ, שֶׁאַתָּה וְשֶׁלְּךָ שֶׁלּוֹ. וְכֵן בְּדָוִד הוּא אוֹמֵר (דברי הימים א כט) כִּי מִמְּךָ הַכֹּל וּמִיָּדְךָ נָתַנּוּ לָךְ. רַבִּי שִׁמְעוֹן אוֹמֵר, הַמְהַלֵּךְ בַּדֶּרֶךְ וְשׁוֹנֶה, וּמַפְסִיק מִמִּשְׁנָתוֹ וְאוֹמֵר, מַה נָּאֶה אִילָן זֶה וּמַה נָּאֶה נִיר זֶה, מַעֲלֶה עָלָיו הַכָּתוּב כְּאִלּוּ מִתְחַיֵּב בְּנַפְשׁוֹ:

...Rabbi Shimon says: He who is walking on the way and repeating his studies, and interrupts his studies and says, "How lovely is this tree! And how lovely is this newly plowed field!" - Scripture considers him as if he is liable for [forfeiture of] his life.

כי הוו מיפטרי מהדדי א"ל ליברכן מר אמר ליה אמשול לך משל למה"ד לאדם שהיה הולך במדבר והיה רעב ועיף וצמא ומצא אילן שפירותיו מתוקין וצילו נאה ואמת המים עוברת תחתיו אכל מפירותיו ושתה ממימיו וישב בצילו
The Gemara relates: When they were taking leave of one another, Rav Naḥman said to Rabbi Yitzḥak: Master, give me a blessing. Rabbi Yitzḥak said to him: I will tell you a parable. To what is this matter comparable? It is comparable to one who was walking through a desert and who was hungry, tired, and thirsty. And he found a tree whose fruits were sweet and whose shade was pleasant, and a stream of water flowed beneath it. He ate from the fruits of the tree, drank from the water in the stream, and sat in the shade of the tree.
וכשביקש לילך אמר אילן אילן במה אברכך אם אומר לך שיהו פירותיך מתוקין הרי פירותיך מתוקין שיהא צילך נאה הרי צילך נאה שתהא אמת המים עוברת תחתיך הרי אמת המים עוברת תחתיך אלא יהי רצון שכל נטיעות שנוטעין ממך
And when he wished to leave, he said: Tree, tree, with what shall I bless you? If I say to you that your fruits should be sweet, your fruits are already sweet; if I say that your shade should be pleasant, your shade is already pleasant; if I say that a stream of water should flow beneath you, a stream of water already flows beneath you. Rather, I will bless you as follows: May it be God’s will that all saplings which they plant from you
יהיו כמותך אף אתה במה אברכך אם בתורה הרי תורה אם בעושר הרי עושר אם בבנים הרי בנים אלא יהי רצון שיהו צאצאי מעיך כמותך:
be like you. So it is with you. With what shall I bless you? If I bless you with Torah, you already have Torah; if I bless you with wealth, you already have wealth; if I bless you with children, you already have children. Rather, may it be God’s will that your offspring shall be like you.

Joyce Meyer*

Consider a tree for a moment. As beautiful as trees are to look at, we don't see what goes on underground - as they grow roots. Trees must develop deep roots in order to grow strong and produce their beauty. But we don't see the roots. We just see and enjoy the beauty. In much the same way, what goes on inside of us is like the roots of a tree.

* Not a Jewish source, just a nice quote!