You are likely already very familiar with the verb kaufen and its antonym verkaufen: 

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Die Leute gehen in den Supermarkt, kaufen etwas und wissen gar nicht, woher es kommt.

People go to the supermarket, buy something and don't even know where it comes from.

Captions 12-13, Bundesregierung - Der Tomatenfisch

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Wir verkaufen Brezeln mit Schokolade.

We sell pretzels with chocolate.

Caption 20, Berlin - Judith und die „Brezel Bar“

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You probably know the verb einkaufen as well: 

Fritzle geht mit seiner Oma einkaufen.

Little Fritz goes shopping with his grandma.

Caption 2, Ivana erzählt Witze - Fritzle und die Oma

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You may, however, be less familiar with the separable verb ankaufen. It is very similar to kaufen ("to buy"), but has a very specific context related to a person or a company that offers to buy items on a regular basis: 

Der Juwelier kauft Gold an.
The jeweler buys gold. 

Der Autohändler kauft Gebrauchtwagen an.
The car dealer buys used cars. 

The separable verb aufkaufen can be used to mean "to buy up" or to buy in large quantities:

Ursprünglich hat er alte Anzüge aufgekauft, so aus den Zwanzigern und so.

Originally, he bought up old suits from the twenties and such.

Caption 6, Jonathan Johnson - Herr von Eden

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The verb aufkaufen is also used when a company takes over or acquires another company: 

Facebook und Amazon wurden von Google aufgekauft.
Facebook and Amazon were acquired by Google.

Please note that the above statement is purely hypothetical and is in no way intended to represent the intention of any companies, real or imagined! 

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Further Learning
Read this excellent article on the four verbs above, and see this list of words that use the root kaufen. You may then go to Yabla German and find examples of the words used in a real world context.

Die Pflanzen blühen jetzt.

The plants are blooming now.

Caption 12, Jahreszeiten - Der Sommer

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After an extremely cold March, Germany experienced temperatures up to 73° F / 23° C this last week. It seems that temperatures below freezing will not return for a while, so it's time for many people to get outside and work in the garden. 

Sein Leben sind die Pflanzen, die er liebevoll rund um sein Häuschen hegt, und das Saatgut, das er daraus gewinnt.

His life consists of the plants that he lovingly tends around his little house and the seeds that he gets from them.

Captions 5-6, Ökobauer - Allein im Wald

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Nitrat ist klassischer Pflanzendünger.

Nitrate is a traditional plant fertilizer.

Caption 26, Bundesregierung - Der Tomatenfisch

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Piggeldy wollte wissen, was Unkraut ist.

Piggeldy wanted to know what a weed is.

Caption 1, Piggeldy und Frederick - Unkraut

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People who live in the city can start planting flowers and herbs on their window sills and on their balconies. 

Ich habe meine Balkonkästen mit dieser Erde gefüllt.

I filled my balcony planters with this soil.

Caption 30, Mülltrennung - in Heidelberg

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Of course, those in the agriculture business (die Landwirtschaft) have already been at work for a while, since their planting and harvesting are hardly limited to the warm months

Und hier sehen wir, wie auf der Domäne Dahlem Landwirtschaft betrieben wird.

And here we see how farming is done at the Domain Dahlem.

Caption 23, Berlin - Domäne Dahlem - Part 1

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Der kleine, freche Rabe Socke flitzt mit seinem Rennwagen durch den hessischen Wald, statt wie seine Freunde bei der Ernte zu helfen.

The little, impertinent raven Socke flies with his race car through the Hessian forest instead of helping with the harvest like his friends.

Captions 2-3, Filmtrailer - Der kleine Rabe Socke

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Further Learning
Search for more vocabulary on Yabla German, or refer to websites such as this one for basic gardening terms, or this thorough list of words related to agriculture.