Bloom（常指供观赏的）N. 花，花朵；V. 开花，如：

1. Roses are in full bloom.

玫瑰花开得正旺. 【名词】

2. Most roses will begin to bloom from late May.

大多数玫瑰从五月末开始开花。【动词】

3. The roses in his garden are blooming beautifully these days.

这些天他家花园里的玫瑰花开得正艳。

【动词】

blossom（尤指果树或灌木的）N. 花朵，花簇; V. 开花，

如：

4. The cherry blossom came out early in Washington this year.

今年华盛顿的樱花开得很早。【名词】

5. Rain begins to fall and peach trees blossom.

开始下雨了，桃树也开花了。【动词】

bloom : 主要指诸如牡丹、玫瑰、梅花、菊花等供观赏的花以及花的状态。

the exotic blooms of the orchid

奇异的兰花

The chrysanthemums are in bloom; some are red and some yellow.

菊花开了，有红的，有黄的。

Roses are in full bloom.

玫瑰花开得正旺。

Azaleas bloom red as a flame.

杜鹃似火。

blossom : 一般指树木开花，尤指果树上开的花。

apple/cherry blossom

苹果花／樱花

The trees are in blossom .

树上鲜花盛开。

There is no blossom this year on the plum trees.

今年李子树不开花。

flower : 指开放的花朵或泛指花卉。

The plant has a beautiful bright red flower.

这株植物开了一朵美丽鲜红的花。

The roses are in flower early this year.

今年玫瑰花开得早。

The crocuses are late coming into flower .番红花开得迟。