AdityavarNe tapaso.adhijAto vanaspatistava vR^ikSo.atha bilvaH |
tasya phalAni tapasAnudantumAyAntarAyAshcha bAhyA alakSmIH || 6
hè Aditya varNe= oh, in sun's splendour, glittering forth - oh, one dazzling in the cerise splendour of rising sun;
tava tapasaH adhijAtaH= by your, hermitic austerities, those that are born; such as;
vanaspatiH= plants, herbs, trees - that give fruits without flower-bearing - [here bilva tree yielding auspicious bilva fruits;
atha= here atha is shubhakara vAchaka, shubhAkshara - those that are auspicious;
bilvaH vR^ikSaH [asti] = bilva, trees [are there, isn't it];
tasya phalAni= its, fruits - bilva fruit of bilva tree;
tapasA= [by the power of your] hermitic austerities;
mA= in my respect - those [a+laskhmi-s] that are available in me;
yA antarA= those, that are inside;
yAH cha bAhyA= those, or else, that are peripheral on my body;
a+lakSmIH= those penuries;
nudantu = cast aside - let those fruits of bilva cast out miseries available either inside or outside of my being.
"Oh, shrI-devi, floridly splendorous like rising Sun, there emerged a vanaspati called bilva tree, for the sake of your undertaking hermetic practises under its shade, isn't it. Let those auspicious bilva fruits cast out penuries available either inside or outside of my being, for they are ripened with the radiance of your austerities... "; such as it is, oh, jAtaveda, this prayer of mine may please be communicated to that numen of plenitude, namely shrI... 
bilva fruits have emerged as j~nAna phalA-s of pArameshvara j~nAnam, where parameshvara is j~nAnamayam where His knowledge itself is tapas - yasya j~nAnamayam tapaH. Hence bilva fruits are called as shrI phala, and trees as shrI vR^iksha-s, and held auspicious. Because those trees have emerged from no les than parameshvara - sA hi sR^IramR^itA - goddess lakshmi chose them for her austerities. Those fruits are chitta doSha hara, remove mental imbalances to madness; shArIra doSha hara, remove bodily problems from skin allergies to leprosy, and they are j~nAna-pradA-s, yielding intellect, thus enabling internal and external plenitude of health. Hence this prayer is for well-being, through bilva media, for their cChAya, dala, phala-s - shade, leaves, and fruits are lively - shrI yukta.
As I said, I think the term "Bilva Vriksha" is just a common appellation for Bilva, because it looks like a tree (Vriksha), even if it doesn't technically meet the Sanskrit definition of Vriksha. So it is called Vriksha by virtue of its appearance, and Vanaspati by virtue of its actual characteristics.