When my bearded iris didn’t bloom much this year, I made a note to divide them in September. It’s on my to-do list. These iris are very special to me as I dug them up the spring after my house burned. One is the Zebra variegated iris with those beautiful blue flowers that smell like grape Kool-Aid. Another is a rich gold one. Now that I think of it, the daylilies didn’t bloom that well this year either, so it’s time to divide them also. What else should I put on my to-do list for this month?
I have a thornless blackberry trained on an arbor over my back steps. Some are still ripening, but later this month I’ll cut back the vines that produced fruit. Canes of the current season should be trained in their place.
Fertilize shrubs lightly one last time if you haven’t already done so last month. All shrubs, especially broad-leaved evergreens, such as rhododendron, pieris, camellia and hebe, need to calm down, stop growing and harden off to get ready for the winter cold. Some plants have already set next year’s buds.
Roses, like my fragrant Compassion, especially appreciate a bit of fertilizer now, encouraging them to bloom another round in October. To keep them blooming make a habit of pinching and pruning off old flowers. Always cut back to an outward facing branchlet with five leaves. There are hormones there that will cause a new rose to grow much sooner than if you cut to one with only three leaves. You can always cut lower on the stem if you need to control height.
Now through October, divide summer blooming perennials like agapanthus, coreopsis, daylily and penstemon that are overgrown and not flowering well. You can also divide spring blooming perennials like candytuft, columbine, astilbe, bergenia and bleeding heart, but sometimes they don’t bloom the first spring afterward due to the energy they use re-establishing themselves. If you’re on a roll out in the garden, though, go for it now.
Spider mites are especially prolific during hot, dry weather. Sometimes you don’t even know how bad the infestation is until all your leaves are pale with stippling. Periodically rinse dust and dirt off leaves with water. Spray the undersides of infected leaves with organics like insecticidal soap switching to neem oil if they build up a resistance to one of the pesticides.
Check lantana, tomatoes and verbena for whitefly. Put out yellow sticky traps to monitor.
Don’t be in a rush to tidy up your late summer garden. Cut back a few of the most prominent plants and leave the rest of the plants with seed heads for wildlife.
Salvia leucophylla (Calfornina native purple sage) is one of our many native salvia whose seedbeds are just as attractive as the flower. Place one at the edge of a border by a path where you might brush against it and enjoy their fragrance.
Time to summer prune fruit trees to control height, maintain shape and eliminate suckers if you haven’t already done so.
Cut back tropical milkweed (Asclepius curassavica) in your garden to encourage Monarch migration. Cut back to 6” and strip foliage.
If your indoor plants have grown too large for their pots, repot them now so they can acclimate through the fall.
Deadhead flowering annuals and perennials in the ground as often as you possibly can. Annuals like zinnias and cosmos will stop blooming if you allow them to go to seed. The same is true of repeat blooming perennials like dahlia, scabiosa, echinacea and lantana. Santa Barbara daisies will bloom late into winter if cut back now.
Jan Nelson, a landscape designer and California-certified nursery professional, will answer questions about gardening in the Santa Cruz Mountains. Email her at ja******@*ol.com, or visit jannelsonlandscapedesign.com.
