बारामासी , literally meaning 'all twelve months' is used for perennials that flower or fruit many times a year, as opposed to plants that do it once a year.
In your context, the reference is to a flowering plant of this kind ( and there are many in different areas) , however you have other plants too called बारामासी , as in बारामासी nimboo: Lemon tree that gives fruit a number of times in a year.

बारहमासी, वि. [हिं.बारह+मास.] 1.बारहों मास होनेवाला।
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बारहमासी or बारमासी means all-seasonal i.e. lasting or active throughout the year.

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Note added at 1 hr (2009-05-07 15:39:46 GMT)
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बारहमासी विशेषण है जिसका अर्थ होता है सदाबहार अर्थात बारह महीनों फलने-फूलने वाला। आपने जिन फूलों का ज़िक्र किया है वे सब सदाबहार या बारहमासी हैं। बारहमासी किसी फूल विशेष का नाम नहीं है।

In Botany plants are classified as 1.annual 2. bienneal and/or 3. perenneal. Annual which literally should mean yearly here has a contextual meaning of living for one season. Bienneal would refer to plants which live for two seasons. Perenneal refers to those plants which live for more than two seasons. Thus Baramasi means perenneals or perenneal plants-the plants living for more than two seasons.

Baramasi lemon (C. lemon [C. limon]) fruits were treated with plant extracts, neem leaf extract (5%), onion extract (5%), garlic extract (5%), neem oil (2%), Eucalyptus oil (2%), Citronella oil (0.1%) and castor oil (10%). Neither different plant extracts and period of storage nor their interaction had any significant effect on breadth and rind thickness of the fruits. The effect of different plant extracts and interaction of plant extract with period of storage on fruit length was also nonsignificant. However, the period of storage had a significant effect on the length of fruits. The length of fruits declined gradually with increase in period of storage. The highest fruit length (5.801 cm) was recorded in the first week while the lowest (5.762 cm) in the 12th week of storage.

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Note added at 2 hrs (2009-05-07 16:47:25 GMT)
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ललित जी मेरे रिप्‍लाई को मुझे बदलना था इसलिए मैने पहलेवाला डिलिट करना चाहा तो आपके कॉमेंट्स ही डिलिट हो गए, मुझे क्षमा करें।

आपके कॉमेंट्स थे: neutral - हर्षे जी, माफ कीजिएगा जिस शोध के एब्सट्रैक्ट पेपर का आपने संदर्भ दिया है दरअसल उसमें बारामासी नीबू की बात की गई है। यहाँ बारामासी फूल का नाम है। बारामासी नीबू की ही तरह बारामासी आम, अमरूद, कटहल इत्यादि की किस्में भी होती हैं।

मेरा रिप्‍लाई यह था: धन्‍यवाद ललित जी, आपकी बात सही है।

a type of a mango, a creeper, climbing plant giving red coloured flowers called "Lal Chameli". A plant providing flowers through twelve months.