Trim spent or faded blooms from alyssum regularly to encourage new blooms. This plant sets seed quickly and will cease blooming if old blooms are not removed. Check every few days and trim away any dying flowers with a pair of scissors or garden shears.
Cut alyssum back by several inches if the ends begin to look ragged or the stem begins to brown. This often reveals fresh new growth that quickly comes alive with new blooms.
Cut neglected alyssum back to a height of 2 to 4 inches to revive the plant in midsummer. Hot dry periods or a few days without watering can leave alyssum brown and unattractive. With a good pruning and attention to regular watering it often revives, producing a flush of new blooms.