Asparagus spears begin emerging when soil temperatures at the crown level start to reach a critical minimum. Asparagus spears grow directly in relation to the average temperature of night and day, and faster as spear length increases. So the taller the spear, the quicker it grows. With warm daytime and nighttime temperatures, asparagus will grow quite rapidly. Make sure to check spears regularly.
High temperatures can cause tall spears to grow much taller by the next day.
Asparagus spears can be harvested by cutting or snapping. Spears usually are cut slightly below the soil level, while snapped spears are broken off at the tenderest point on the lower stem- usually about a inch above the soil level. The asparagus plant sends up new spears to replace the cut or snapped spears as soon as they have been removed. The lower part of the asparagus spear is fairly heavy, so you will harvest more weight when you cut the spears. But the lower part of the spear is usually tough and woody and usually must be discarded.