People worship the Perumal in various forms like the sun, fire, and water, Idols etc. We not only offer Him the bhakti but also dedicate him Neivedhyams (Prasadhams), Vastharams (Silk clothes), Flowers etc. But out these, flowers are considered to be the greatest and affordable by all kinds of peoples.
There is a great meaning behind the flower worship. By offering flowers, which are naturally scented, our mind and soul which are covered by evil thinkings and bad feelings are cleared by means of this soft flowers and thereby dedicating ourselves with great bhakti towards the Perumal.
Thulasi, Vilvam, Virukshi etc are some of the divine flowers, which are generally dedicated to the Perumal.
Thulasi is considered to be sacred amongst all and it is believed that Sriman Narayanan reside in it. By offering this sacred Thulasi to Sriman Narayanan during Fridays and Saturday, we get his great blessings.
Even in great Sri Vaishnavite temples, knowing the greatness of flowers, Nandhavanams (flowers park) are maintained and the flowers taken from here are tied as garlands and offered to the Perumal. Added to this during Bramhotsavam, the Perumal is taken out in Pallakku which is constructed and designed with great flower which is referred to as "Pushpa Pallakku". This Vaghanam is considered one among the great Vaghanam during Bramhotsavam.
Great Aacharyan - Sri Ananthan Pillai as ordered by Srimath Ramanujar performed this Nandhava Kainkaryam in Tirumala - Tirupathi. Even, today we can find his Nandhavanam in Tirumala.
So, bhaktas while going to temples, even if you could not dedicate lots of offerings to the Perumal, never get disturbed (or) worried, just offer him with some flower and a great bhakti to him which is considered to be precious then all.