How do I write a topic sentence and a concluding sentence in a short essay?I have to write essays with one topic sentence, 3 reasons with 2 details...

When writing a topic sentence you have to determine first what you want to discuss.  For example; There are two types of plants, perennial and annual. 

Next you said that you needed to develop at least three sentences.  Before I even added my topic I thought out things about it.   I know the following;

-perennial plants continue to grow

-annual plants have to be replanted yearly

-both are attractive in gardens

Now I have to add three sentences to my topic sentence.

There are two types of plants that can be put in a garden perennial and annual.  Perennial plants will continue to grow year after year.  Annual plants die out at the end of a season and need to be repurchased for planting the following year. No matter which type of plant a gardener decides to purchase, the plants are offered in beautiful varieties.

Now I need a closing sentecne.  I want to look at my topic sentence to renew my information.  For example:

Using both perennial and annual plants will make a garden beautiful and allow for some plants to continue to grow while others will need yearly replacement.

There are two types of plants that can be put in a garden, perennial and annual.  Perennial plants will continue to grow year after year.  Annual plants die out at the end of a season and need to be repurchased for planting the following year. No matter which type of plant a gardener decides to purchase, the plants are offered in beautiful varieties.  Using both perennial and annual plants will make a garden beautiful and allow for some plants to continue to grow while others will need yearly replacement.