Southwest Zone Planting

It has been more than 10 years since a fellow horticulturist, H. Pruet of Studio City, CA wrote to us with his techniques of growing tree peonies in zone 9 California. His ideas created quite a stir on the West Coast, because most gardening books at the time dismissed the tree peony with the herbaceous peony in needing real freezing weather to produce good blooms. Since then, we have shipped hundreds of plants to customers in zone 9 northern and southern California, Nevada, northern Florida, Texas and Arizona with excellent results.

Herbaceous peonies do need more days with freezing temperatures to produce good flowers. We do not reccommend them beyond zone 8., though some micro-climates of zone 9 will grow herbaceous peonies.

Tree peonies, on the otherhand, will grow well with winter lows in the 30's and 40's F. The secret here is to force the peony into dormancy by trimming off the leaves in November if they do not fall on their own. Do not cut the woody stems, just trim the leaf stems off the woody main stems. This mimics the deciduous leaf drop in colder areas and cycles the plant into producing new flower buds. During this time, it is best to withold water and any feeding.

As the days of January get longer, the plant will respond with new spring growth. Blooms occur in Zone 9 in late February to mid- March in warmer areas, and late March to mid- April.

USDA Zone 9 and 10 can be further divided into their western Sunset Zones up to zone 24. We suggest that tree peonies be planted in those zones with a pronounced winter chill, that is zones 3 to 22. In the warmer zones, planting in cold air pockets such as at the base of hills can extend the growing range. In most of zone 9, late Spring, Summer and early Autumn irrigation is required. This is best accomplished by hand or drip irrigation at approximately one gallon per plant every other day with good drainage. Mulching aids in decreasing evaporative loss. The plants should be shielded from direct afternoon sun past 1-2 pm.