Naked Spike Ambrosia

Naked Spike Ambrosia (Ambrosia psilostachya) should be watered deeply to ensure that the soil is evenly moist. The plant should be watered once a week during the hotter months of the year. During the cooler months watering should be reduced to about every 2 weeks or when the soil appears dry. Additionally, avoid overwatering the plant as it is prone to root rot.

Naked Spike Ambrosia (Ambrosia psilostachya de) prefers full sun to partial shade. It will tolerate full shade, but it may become leggy and produce fewer flower heads. This plant needs at least 8-10 hours of sunlight each day, ideally in the morning, to ensure robust flowering. In northern climates, the plant should receive some afternoon shade to protect it from strong winds and direct sunlight in the warmer months. Morning sun is best for this species as direct afternoon sun and heat may cause the leaves to droop and weaken the plant. It is important that the soil is also well drained to avoid root rot.

Naked Spike Ambrosia should be pruned in early spring, just as the plant is beginning to bud. Pruning should be done with sharp, clean shears and should include removal of dead or damaged stems. Side shoots should also be pruned off and the top of the plant should be cut back to encourage a fuller shape. To keep the plant’s size and shape in check, pruning should be done every 2 to 3 years, starting when the plant is around 1 year old. Prune the plant by removing any straggly or dead stems. Also, shapes the plant, cutting back the tips of the stems to encourage branching and remove any damaged foliage. Pruning back will help the plant remain neat and compact in size.