Sentence:  Geoff might prefer to "take control": to collect seed and sow it next spring, <WSD>pricking</WSD> out a few of the best seedlings, growing them on in pots next summer before planting them out in the autumn. 
Meaning of the word marked with <WSD> tags:  "Usually in the form" '''prick out''': to plant (seeds or seedlings) in holes made in soil at regular intervals.