The Kiznaiver site just posted the official flowers the girls are holding and confirmed their meaning will help us better understand the series.
Nico: Agapanthus543Please respect copyright.ＰＥＮＡＮＡh1zuw9IhOW
Honoka: Zinnia543Please respect copyright.ＰＥＮＡＮＡ5k6aSk4zoI
Chidori: China aster543Please respect copyright.ＰＥＮＡＮＡX6PKuEjRZe
Noriko: Roses
So I did some Hana kotoba google’ ing. Here’s a brief (second) look at their meaning below the cut!
Nico
The Agapanthus is known as the “flower of love”. Its meanings include 「the arrival of (romantic) love (恋の訪れ)」, 「love letter（ラブレター）」 and 「intellectual attire/guise （知的な装い）」. It’s said that this last meaning comes from the refreshing and delicate appearance of the pale purple/blue flowers. 543Please respect copyright.ＰＥＮＡＮＡe8xtiisDXA
Source: [x]
Honoka
「thoughts of absent friends（不在の友を思う）」543Please respect copyright.ＰＥＮＡＮＡEN51cBJqnx
「I mourn your absence（あなたの不在を悲しむ）」543Please respect copyright.ＰＥＮＡＮＡ3lzafznhnh
「Don't be off your guard (注意を怠るな)」543Please respect copyright.ＰＥＮＡＮＡ7X4WncewTu
Source: [x]
“Thoughts of friends or thoughts of a missing friend are the most common meanings for the zinnia.“ Yellow zinnias mean “daily remembrance”.543Please respect copyright.ＰＥＮＡＮＡxMyDa9yZTG
Source: [x]
Chidori
General meaning:543Please respect copyright.ＰＥＮＡＮＡufMNvpMlOS
• 「Change (変化)」543Please respect copyright.ＰＥＮＡＮＡDYTgckva7j
• 「Reminiscence (追憶)」543Please respect copyright.ＰＥＮＡＮＡnYQ65wYlHi
• 「Agreement / Sympathy (同感)」543Please respect copyright.ＰＥＮＡＮＡvXi3QMaPhM
• 「Belief in (romantic) Love (信じる恋)」
Occidental meaning:543Please respect copyright.ＰＥＮＡＮＡEe4HYIXWiP
• 「Variety（多様性、変化）」543Please respect copyright.ＰＥＮＡＮＡq7QdCpcIKd
• 「Fidelity（忠実、貞節）」543Please respect copyright.ＰＥＮＡＮＡZDbW1w9gpf
• 「I will think of you（私はあなたを想うでしょう）」
Color meaning:543Please respect copyright.ＰＥＮＡＮＡyDCQa5Q5KF
• White: 「Please believe me (私を信じてください)」543Please respect copyright.ＰＥＮＡＮＡg3oFCdMgCb
• Purple: 「Victory of (romantic) love (恋の勝利)」, 「My love is deeper than yours (私の愛はあなたの愛より深い)」543Please respect copyright.ＰＥＮＡＮＡcy4ElMsUBg
Source: [x]
Noriko
It’s hard to tell whether Noriko is holding orange roses or yellow ones, so I’m including both!
General meaning:543Please respect copyright.ＰＥＮＡＮＡXfyu5ai5YL
• 「Love (愛)」543Please respect copyright.ＰＥＮＡＮＡwQuyJvXdhp
• 「Beauty (美)」543Please respect copyright.ＰＥＮＡＮＡGU39KT5aln
Source: [x]
Color meaning:543Please respect copyright.ＰＥＮＡＮＡGnfT7a2kuv
• White: 「 Purity / Chastity( 純潔)」, 「I am worthy of you (私はあなたにふさわしい)」, 「Deep respect (深い尊敬)」
• Green: 「Calm / Gentle (穏やか)」, 「You can have hope (あなたは希望を持ちえる)」
• Orange: 「Innocence（無邪気）」, 「Bonds / Kizuna （絆）」, 「Healthy（健やか）」, 「Trust / Faith （信頼 ）」.
• Yellow: 「Decrease of love（愛情の薄らぎ）」, 「Jealousy （嫉妬）」, 「Friendship （友情）」, 「Devotion （ 献身 ）」, 「Tired / Weary of (romantic) love （恋に飽きた）」.543Please respect copyright.ＰＥＮＡＮＡ1CAsMnUvOs
Source: [x] & [x]
and then Add to home screen.