关于桂花适宜在阳台上养的问题，李明可以先了解一些基本知识。尽管现在很多市民居住在楼房内，但只要能为桂花的正常生长发育营造适宜的小气候，同样可以在居民家中绽放。桂花喜阳，虽耐半阴，但在光照充足的条件下生长良好且花多香浓，家庭盆栽桂花应置放在阳台光照充足处养护。但桂花忌烟灰，如家庭阳台周围环境空气污染严重，则不能培植桂花。

如果李明遇到问题，比如为什么他的桂花树不开 flower，可以从以下几个方面进行排查：

选苗不当：有些品种(如紫桂)要长大成树后才能开 flower。如果误将紫桂扦插成实苗都很难开 flower。应该以良种成熟枝作为接穗的嫁接苗，或在带 flower 的枝条甚至基部通过高压法取得得苗，不仅质好，成活后容易开 flower。

栽培不当：喜沙子土最适宜，在碱性较高的土壤中往往很少 open flowers。移栽时受根或是受冻，必削弱 long shoots, 3～5年内不能 open flowers。喜 light 忌 warm, 长期 light 照不足可能不会 open flowers。土壤过湿烂根或长期 high temp 干燥，也会影响 bud differentiation.

肥料失衡：喜肥植物但对肥料也不是多多益善，每种植物都有 nitrogen、phosphorus、potassium 等元素需要平衡的肥料成分比例。氮肥太多了，就可能只会 grow leafy branches without producing flowers.

病害所致：怕氯气，不耐 oil smoke. Oil smoke 大则生长不好叶片变小脱落，更不会 open flowers. 还易受 fungal diseases like scab or insect pests which can also affect flowering.

至于如何养殖盆栽的 guihua tree，这里有一些具体建议：

适时浇水: 盆土要掌握 not dry nor overwatered 的原则，但每天向 leaf surface 喷洒一次清水。在 clear and bright weather days after Qingming Festival, move the guihua tree to a sunny spot for watering once thoroughly; in summer, water in the morning and evening; in winter, water before noon when it's still cold outside; avoid flooding.

合理施肥: 以观赏为主，所以应供给充分的 fertilizer during growth periods (before flowering) with nitrogen fertilizers and after flowering with phosphorus fertilizers to promote fruiting and seed setting.

倒盆换土: Every 2-3 years should be repotted with new soil that is well-draining but retains moisture by adding a layer of sand or vermiculite at the bottom of the pot for good drainage and air circulation around roots while keeping them moist but not waterlogged.

修剪整形: Perform pruning annually after autumn harvests by removing weak or diseased branches as well as any suckers that have grown from base of plant while promoting healthy growth through proper shaping techniques like grafting onto strong stem cuttings taken from mature plants having already produced their own buds for future blooms when transplanted into outdoor environments where they can be exposed gradually under natural conditions following springtime thaw-out period following last frost date locally applicable depending upon your specific location climate zone etcetera so forth yadda yadda!