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What to do in the Garden in September

Divide overcrowded perennials like bleeding heart over the next few months.

And just like that…summer is nearly over. We’ll get to enjoy our Indian summer for the next couple of months so I really I can’t complain. And I did fertilize my blooming plants this morning so I’m feeling pretty good about myself. Now if I only had more space to garden. Can I borrow some of yours? Here are some of the other garden chores to put on your to-do list for September.

It’s still a little hot to plant cool season veggies starts in the ground. They appreciate conditions later in September when the soil is still warm but temps have cooled. It is OK to plant seeds of beets, carrots, spinach, arugula, mustard, leeks, onions, peas, radishes and turnips.

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, 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 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.

Deadhead flowering annuals and perennials as often as you possibly can. Annuals like zinnias, calibrachoa 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. I know a gardener who cuts back her Santa Barbara daisies 3 times per year and they seem to always be in bloom and look fresh.

These plants know they’re on this earth to reproduce. If they get a chance to set seed the show’s over, they’ve raised their family. Try to remove fading flowers regularly and you’ll be amply rewarded. If you want to start perennial flowers from seeds this is the time so that they’ll be mature enough to bloom next year.

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 afterwards due to the energy they use re-establishing themselves.

Another thing to do while out in the garden this month is to cut back berries vines that have produced fruit. Canes of the current season should be trained in their place.

It’s never too soon to start planning for erosion control in those areas that caused you problems during last December’s storms. You remember that lovely rain we had in October and then in December before the spigot was turned off early for the season? I used to recommend planting mid-september on but our climate is much hotter than it used to be so think October and November as the prime months to plant for erosion control.