Late Summer Gardens, Part II

Last month, this column covered some tips on design and care of the late summer garden. A month later and we are still in the same late summer weather pattern, with mostly foggy days on the western side of the city, dry soils, and cool temperatures. As each week of late summer passes, the summer-dry garden looks more and more disheveled and dreary, unless the gardener follows a few simple rules.

Rule #1: Plan for this time of year, which is the most challenging for the summer-dry gardener. There are a few special plants which are at their blooming best this time of year and they are precious for us fog-dwellers.

Because many San Francisco gardens are small, vertical space is very important when filling a garden visually. Some of the brightest performers at this time of year are vines. Semi-tropical bougainvillea vines are blooming brilliantly now with great splashes of crimson and purple and blood-red trumpet vine adds to the bright scarlet medley. Both these vines need some summer water until they are established, and then can go dry, especially near the coast. Give them some support with a sunny fence to climb and they will delight the late summer garden for years to come.

BLood-red trumpet vine.

BLood-red trumpet vine.

As the days begin to shorten, the beautiful princess flower begins to perk up. A large shrub or small tree covered with big brilliant purple flowers at this time of year, princess flower is looking good in the late summer garden as other plants are fading. In small San Francisco gardens with dry summer soils and lots of shady spots, princess flower can be a problem-solver. It prefers to have its roots in a shady spot, and then grow up until its crown is in the sun, so it is an excellent choice in the shade from a north facing fence. It needs some summer water to help it get established, and then mature plants can weather our dry summers, especially near the coast.

Another beautiful accent in the late summer garden comes from ornamental grasses. Many of these are very comfortable in dry soils, and bloom in the late summer adding their graceful or erect textures to the garden scene. Red fountain grass (Pennisetum rubrum) is blooming now, as is Japanese silver grass (Miscanthus sinensis). The flowers of both these grasses are beautiful enough to cut for flower arrangements.

Rule #2: Finish any leftover clean-up from winter and spring. Last month’s column covered deadheading, or removing faded blossoms to lighten the visual load of brown, grey, dying and fungus affected plants in the garden. Another tip to help open up the late summer garden visually is to finish cutting back cool season plants which are dying back, in some cases removing everything that’s above ground.

During the rainy season, many garden plants complete their vegetative growth, and then bloom in spring as the rains are ending. Plants with this seasonal pattern may be completely dormant and resting in the soil now, either as bulbs or corms in the case of perennials, or as seeds in the case of annuals. In these cases, it is safe to remove all the withered leaves and stems from last winter and spring, creating more freshness and space in the late summer garden.

Some examples of summer-dry bulbs which follow this pattern are Watsonia (bugle lily), Chasmanthus (Adam’s rib), and Sparaxis (harlequin flower). Last year’s leaves and stems can be cut right down to the ground once they have turned mostly brown. Many gardeners have already done this, but if the faded plants are still taking up visual space in your yard, now is the time to cut them down, before the new green shoots of next year’s plants begin to emerge.

Traditional spring bulbs, such as tulips and crocuses, are available in nurseries now. But these bulbs which have to be dug out, refrigerated, and replanted every year are not a permanent solution in a sustainable garden. They simply are not a match for our climate because they grow best where there are cold winters. This year might be a great time to at least try some of the less well-known bulbs, like those in the preceding paragraph, which thrive all by themselves in our climate, and come back more vigorously year after year. There’s nothing wrong with getting a few tulips, too, for old time’s sake.

Rule #3: Some cool season plants do not need to be removed entirely, but they will benefit from being cut back hard at this time of year. Many perennials that grew during the rainy season and bloomed in winter or spring are now faded, over-grown, and sprawling. By cutting these plants back hard, leaving only a few sturdy branches with a few leaves on them, the gardener can both prepare these plants to do their best in the coming rainy season and also clear up the fading jumble of the late-summer garden.

African daisies.

African daisies.

Some examples of plants that can benefit from being cut back hard now as we head into the shorter days of fall include forget-me-nots and primroses on the shady side of the garden, and African daisies on the sunny side. If given a good haircut now, these plants will delight you with fresh, full leafy growth in winter followed by bright flowers in February and March.

Cutting back cool-season perennials will also clear and clean the late summer garden, and let your Japanese anemones, Tritonia, lantana, and other late summer and fall blooming perennials stand out.

Japanese anenome.

Japanese anenome.

Rule #4: Feed the soil where you have cut back hard and removed lots of debris. Organic gardeners know that you cannot keep removing bucket after bucket of garden debris and trimmings without putting something back into the soil. Ideally, our garden debris goes into the compost pile, and recycles back into the soil as finished compost. But for many home gardeners, the garden debris goes into the city green bin, is composted by the city, and ends up building the soil in a vineyard in Sonoma instead.

Composts, manures, and other soil amendments are available in nurseries bagged, and adding some form of organic soil amendment or mulch to the garden after a big clean-up is simply part of the cycle of gardening. Fall is a great time to add mulches and soil amendments in the garden because winter rains will help carry the nutrients deep into the soil. Purchased soil improvers can become expensive, though, and so we often tend to use less than is really needed.

Sometimes it works to go in with neighbors, and get a big delivery of compost or manure and share it between several gardens. It’s more affordable that way. Some stables will deliver manure for free if they can drop off a whole truck-load. Mushroom compost (my personal favorite) can be delivered by the cubic yard or sometimes half yard. Try American Soil in Richmond, Mar Vista Stables in Daly City, or Sea Horse Ranch in Half Moon Bay. These are just a few starting points; there are many more resources out there to be discovered.

By following these few simple rules, the late summer/early fall garden can be turned from a dreary, cluttered and unhealthy place into a little paradise, just waiting for the first drops of autumn rain.