One can cultivate a garden. Anyone who has land—in India, at least, any poor man has a certain amount of land—can utilize that for Kṛṣṇa by growing flowers to offer Him. One can sow tulasī plants, because tulasī leaves are very important and Kṛṣṇa has recommended this in Bhagavad-gītā. Patraṁ puṣpaṁ phalaṁ toyam. Kṛṣṇa desires that one offer Him either a leaf, or a flower, or fruit, or a little water—and by such an offering He is satisfied. This leaf especially refers to the tulasī. So one can sow tulasī and pour water on the plant. Thus, even the poorest man can engage in the service of Kṛṣṇa.
(Bhagavad-Gita------11:55------purport).

The importance of tulasī leaves is very clearly mentioned here. Tulasī plants and their leaves are very important in devotional service. Devotees are recommended to water the tulasī tree every day and collect the leaves to worship the Lord. One time an atheistic svāmī remarked, "What is the use of watering the tulasī plant? It is better to water eggplant. By watering the eggplant one can get some fruits, but what is the use of watering the tulasī?" These foolish creatures, unacquainted with devotional service, sometimes play havoc with the education of people in general.
(Srimad Bhagavatam------3:19:15-------purport).

One should worship the Lord by offering pure water, pure flower garlands, fruits, flowers and vegetables, which are available in the forest, or by collecting newly grown grasses, small buds of flowers or even the skins of trees, and if possible, by offering tulasī leaves, which are very dear to the Supreme Personality of Godhead.
It is specifically mentioned herein that tulasī leaves are very dear to the Supreme Personality of Godhead, and devotees should take particular care to have tulasī leaves in every temple and center of worship. In the Western countries, while engaged in propagating the Kṛṣṇa consciousness movement, we were brought great unhappiness because we could not find tulasī leaves. We are very much obliged, therefore, to our disciple Śrīmatī Govinda dāsī because she has taken much care to grow tulasī plants from seeds, and she has been successful by the grace of Kṛṣṇa. Now tulasī plants are growing in almost every center of our movement.
(Srimad Bhagavatam------4;8;55-------translation and purport).

Through devotional service one can easily please Lord Kṛṣṇa with a leaf of the tulasī plant and a little water. As the Lord says in the Bhagavad-gītā (9.26), a leaf, a flower, a fruit or some water (patraṁ puṣpaṁ phalaṁ toyam), when offered with devotion, very much pleases Him. He universally accepts the services of His devotees. Even the poorest of devotees in any part of the world can secure a small flower, fruit or leaf and a little water, and if these offerings, and especially tulasī leaves and Ganges water, are offered to Kṛṣṇa with devotion, He is very satisfied.
(Sri Caitanya Caritamrta------1:3:107------purport).

A dog naturally does not become a devotee at any time, but still it is sometimes found that a dog of a devotee gradually becomes a devotee also. We have actually seen that a dog has no respect even for the tulasī plant. Indeed, a dog is especially inclined to pass urine on the tulasī plant. Therefore the dog is the number one nondevotee. But Śrī Caitanya Mahāprabhu's saṅkīrtana movement is so strong that even a doglike nondevotee can gradually become a devotee by the association of a devotee of Lord Caitanya.
(Sri Caitanya Caritamrta------1:10:1-------translation).

"After planting the tulasī tree before your house, you should daily circumambulate that tulasī plant, serve her by giving her water and other things, and continuously chant the Hare Kṛṣṇa mahā-mantra."
This is the beginning of spiritual life. After leaving householder life, one may go to a holy place, such as the bank of the Ganges or Yamunā, and erect a small cottage. A small cottage can be constructed without any expenditure. Four logs serving as pillars can be secured by any man from the forest. The roof can be covered with leaves, and one can cleanse the inside. Thus one can live very peacefully. In any condition, any man can live in a small cottage, plant a tulasī tree, water it in the morning, offer it prayers, and continuously chant the Hare Kṛṣṇa mahā-mantra. Thus one can make vigorous spiritual advancement. This is not at all difficult. One simply has to follow the instructions of the spiritual master strictly. Then everything will be successful in due course of time. As far as eating is concerned, there is no problem. If Kṛṣṇa, the Supreme Personality of Godhead, supplies everyone with eatables, why should He not supply His devotee? Sometimes a devotee will not even bother to construct a cottage. He will simply go to live in a mountain cave. One may live in a cave, in a cottage beside a river, in a palace or in a big city like New York or London. In any case, a devotee can follow the instructions of his spiritual master and engage in devotional service by watering the tulasī plant and chanting the Hare Kṛṣṇa mantra. Taking the advice of Śrī Caitanya Mahāprabhu and our spiritual master, Bhaktisiddhānta Sarasvatī Gosvāmī Mahārāja, one can go to any part of the world and instruct people to become devotees of the Lord by following the regulative principles, worshiping the tulasī plant and continuously chanting the Hare Kṛṣṇa mahā-mantra.
(Sri Caitanya Caritamrta------2:24:261-------translation and purport).

Haridāsa Ṭhākura constructed a cottage in a solitary forest. There he planted a tulasī plant, and in front of the tulasī he would chant the holy name of the Lord 300,000 times daily. He chanted throughout the entire day and night.
The village of Benāpola is situated in the district of Yaśohara (Jessore), which is now in Bangladesh. Benāpola is near the Banagāṅo station, which is at the border of Bangladesh and may be reached by the Eastern Railway from Sealdah Station in Calcutta. Haridāsa Ṭhākura, being the ācārya of chanting the Hare Kṛṣṇa mahā-mantra, is called Nāmācārya Haridāsa Ṭhākura. From his personal example we can understand that chanting the Hare Kṛṣṇa mantra and becoming highly elevated in Kṛṣṇa consciousness is very simple. Without difficulty one can sit down anywhere, especially on the bank of the Ganges, Yamunā or any other sacred river, devise a sitting place or cottage, plant a tulasī tree, and before the tulasī chant the Hare Kṛṣṇa mahā-mantra undisturbed.
Haridāsa Ṭhākura used to chant the holy name on his beads 300,000 times daily. Throughout the entire day and night, he would chant the sixteen names of the Hare Kṛṣṇa mahā-mantra. One should not, however, imitate Haridāsa Ṭhākura, for no one else can chant the holy name 300,000 times a day. Such chanting is for the mukta-puruṣa, or liberated soul. We can follow his example, however, by chanting sixteen rounds of the Hare Kṛṣṇa mahā-mantra on beads every day and offering respect to the tulasī plant. This is not at all difficult for anyone, and the process of chanting the Hare Kṛṣṇa mahā-mantra with a vow before the tulasī plant has such great spiritual potency that simply by doing this one can become spiritually strong. Therefore we request the members of the Hare Kṛṣṇa movement to follow Haridāsa Ṭhākura's example rigidly. Chanting sixteen rounds does not take much time, nor is offering respects to the tulasī plant difficult. The process has immense spiritual potency. One should not miss this opportunity.
(Sri Caitanya Caritamrta------3:3:100-------translation and purport).

After offering her obeisances to the tulasī plant and Haridāsa Ṭhākura, she sat down at the door. Hearing Haridāsa Ṭhākura chanting the Hare Kṛṣṇa mantra, she also chanted, "O my Lord Hari, O my Lord Hari."
Herein one can clearly see how a Vaiṣṇava delivers a fallen soul by a transcendental trick. The prostitute came to pollute Haridāsa Ṭhākura, but he took it as his duty to deliver the prostitute. As clearly demonstrated here, the process of deliverance is very simple. With faith and reverence the prostitute associated with Haridāsa Ṭhākura, who personally treated her material disease by chanting the Hare Kṛṣṇa mahā-mantra. Although the prostitute had an ulterior motive, somehow or other she got the association of a Vaiṣṇava and satisfied him by occasionally chanting in imitation, "O my Lord Hari, O my Lord Hari." The conclusion is that associating with a Vaiṣṇava, chanting the holy name of the Lord and offering obeisances to thetulasī plant or a Vaiṣṇava all lead one to become a transcendental devotee who is completely cleansed of all material contamination.
(Sri Caitanya Caritamrta------3:3:122-------translation and purport).

"Chant the Hare Kṛṣṇa mantra continuously and render service to the tulasī plant by watering her and offering prayers to her. In this way you will very soon get the opportunity to be sheltered at the lotus feet of Kṛṣṇa."
(Sri Caitanya Caritamrta------3:3:137-------translation).

In the Skanda Purāṇa it is directed that a devotee should offer water to the tulasī plant and āmalaka trees. He should offer respect to the cows and to the brāhmaṇas and should serve the Vaiṣṇavas by offering them respectful obeisances and meditating upon them. All of these processes will help the devotee to diminish the reactions to his past sinful activities.
(Nectar of Devotion).

The gopīs then addressed the tulasī plants: "Dear tulasī, you are much beloved by Lord Kṛṣṇa because your leaves are always at His lotus feet. Dear mālatī flower, dear mallikā flower, dear jasmine flower, all of you must have been touched by Kṛṣṇa while He was passing this way after giving us transcendental enjoyment. Have you seen Mādhava passing this way? O mango trees, O trees of jackfruit, O pear trees and āsana trees! O blackberries and bael trees and trees of the kadamba flower—you are all very pious trees to be living on the bank of the Yamunā. Kṛṣṇa must have passed through this way. Will you kindly let us know which way He has gone?"
(Krsna Book).