UNITED STATES—Native plants like coast live oak, valley oak, toyon, flannel bush, Western redbud and California lilac (ceanothus) are among the most resilient of plants as the weather gets dry and warm after spring. So are plants from similar climates, like bottlebrush, oleander, rockrose, grevillea, acacia and eucalyptus. They survive dry summers by dispersing their roots deeply into soil that does not get as desiccated as surface soil naturally does (without irrigation).
Ironically, these most resilient plants can also be difficult to work with while they are young. Because they rely on extensive root dispersion for survival, new plants that have not yet dispersed their roots can not survive long without regular watering. They only become tolerant to drought as their roots disperse into deeper soil.
However, because they are adapted to arid conditions, they do not like to be too damp for too long. Roots soon rot in soil that does not drain adequately between watering. They therefore need to be watered frequently, but not too frequently. Yes, that is as confusing as it sounds.
To make it even more confusing, these plants will need less watering as they mature and disperse their roots. Bottlebrush, oleander, contoneaster, hop bush, firethorn, grevillea and juniper can certainly tolerate more water than they really need; but wasting water is contrary to selecting drought tolerant plants to conserve water. Manzanita, coyote brush, rockrose, flannel bush and redbud may actually succumb to rot if watered too much. Even perennials like Pacific coast iris and yarrow can have problems.
Pine, oak, acacia and especially eucalyptus disperse their roots as soon as they can, so do not want to be confined in containers. It is therefore best to plant smaller young specimens than larger ones. #5 (5 gallon) eucalypti get established in the garden more efficiently than larger but more expensive #15 (15 gallon) trees. If #1 trees were available, they would be even better.
highlight: African daisy
Only a few decades ago, the only familiar African daisies, Osteospermum spp., were the sprawling and often sparsely branched ‘freeway daisies’ with blue-eyed white or rarely light purple flowers. They made nice blooming ground cover that could be planted in drifts for a bit of color among the deep green of Algerian ivy on expansive freeway embankments.
Modern varieties are shrubbier perennials with more profuse bloom of white, cream, pink, purple, pale yellow or pale orange flowers, mostly with blue or purple centers. Some yellow flowers have yellow or cream centers. Some of the fancy types have spooned petals like some types of cosmos or chrysanthemums. After the primary bloom phase in spring, a few sporadic flowers may continue to bloom through summer until the secondary light bloom phase late in summer. However, the old fashioned ‘freeway daisy’ types do not always display a second bloom phase. Varieties with variegated foliage are still rather rare.
Even though African daisies can survive in inferior soil with minimal watering, they perform best with good soil and regular watering. Plants in containers can not disperse their roots like they want to, so are are more dependent on regular watering. Fertilizer prolongs bloom.