Slope Planting with Agaves and Daylilies

Agave ‘Blue Glow’

octopus agave (Agave vilmoriniana)

daylily

double orange daylily

Myoporum parvifolium

“Last October, I had the ivy on my front slope chopped to the ground and covered with landscape fabric. I recently took off the fabric and chopped out a lot of dead vines and roots, although I came nowhere close to getting it all. A lot of people say not to bother fighting the ivy, but I read a column of yours where it said that if I just stay on top of it, it should be OK. I was wondering about what to plant there. Some large succulents? I have morning shade until 10-11 am. One of my neighbors has succulents growing with the same amount of sun exposure.”
Robert Lowman, Santa Clarita

After chopping out the ivy, you were wise to lay down landscape fabric, which is primarily used for weed control. For those who might not know, this fabric is made of polyetyhlene and is typically rolled out on slopes or flat ground prior to planting. You cut a hole in the fabric wherever you place a plant, the idea being that the fabric which surrounds your plants will prevent regrowth of troublesome perennial weeds (such as Bermuda grass) or ground covers (such as ivy) by starving them of light. At the same time, new weeds will not invade the area since their roots will not be able to pentrate the fabric from above. Although it has been demonstrated that weeds and old ivy will eventually grow through the fabric, as long as you are alert and spray the weeds or pull the ivy as soon as they appear, you will be able to stay in control of the situation. Landscape fabric will also help to retain soil moisture, especially when it is covered with several inches of mulch.

There is also a spray product called Roundup Poison Ivy Plus Tough Brush Killer that has been introduced for the express purpose of eliminating invasive weeds, brush, and ground covers of every type, including English (small to medium sized, finely cut leaf) and Algerian (big, floppy leaf) ivy. If you are reluctant to use chemicals, you will need to commit yourself to hand pulling your ivy but, again, if you pull it at the first sight of any new leaf, you will not find the task to be a burden.

As far as slope planting ideas, it’s always a good idea to walk around the neighborhood, as you have done, to see what is growing in a microclimate similar to yours. You notice plants growing on a similar terrain with the same amount of sun exposure, make a note of which plants you find especially attractive in those locations, and plant them in your own garden. Bear in mind that slope planting is advantageous due to the fact that cold air, like water, moves downhill so that marginally hardy plants, when planted on slopes, may escape frost damage on cold nights. The biggest challenge with slope planting is water run off so if you have conventional spray or rotary sprinklers, you may have to run several short irrigation cycles in succession in order to properly hydrate the soil, without seeing your slope erode from over watering.

A simple way to avoid slope run-off is through drip irrigation. If you go ahead and plant large succulents such as agaves, you might consider placing a drip emitter on the uphill side of each plant. You will water significantly less than you would with conventional sprinklers and water will be there exclusively for your planted specimens, and not for the empty space between them. After your succulents are established in a year or two, watering may be all but unnecessary. Just keep in mind that, in any drip system, a filter and pressure regulator are needed in order to keep your drip lines clean and performing properly.

While many succulents can handle Santa Clarita cold, others, such as the ever popular blue chalk sticks (Senecio serpens), cannot. You will want to check the cold tolerance of each of your selections to make sure they are compatible with Santa Clarita winters.

Speaking of succulents, the thought of agaves may conjure up unruly century plants (Agave americana), the largest agave species, the one with messy, asymmetrical strap-shaped leaves, either all blue or with a yellow stripe down the middle. But there are also soft leaved species, such as octopus agave (Agave vilmoriniana) worthy of consideration, as is Agave ‘Blue Glow,’ a luminous rosette growing only two feet tall whose blue-green leaves are thinly margined in yellow and red. And don’t forget about Agave filifera and Agave multifilifera, endlessly fascinating with their mantle of curly white hairs. These four Agaves, as well as many other, but not all, Agave species, should handle Santa Clarita winters just fine.

Other possibilities for slope planting in your area include flower carpet roses, trailing rosemary (Rosmarinus officinalis ‘Prostratus’), Myoporum parvifolium, and dwarf coyote brush (Baccharis pilularis ‘Twin Peaks II’). I would also consider daylilies if I were you. The strongest daylilies produce yellow or orange blooms, although dozens of varieties, in many colors, are available. One outstanding benefit of daylilies is that they provide cut flowers for vase arrangements throughout the growing season.

Tip of the Week: It happens that many parts of a daylily (Hemerocallis spp.) are edible. Throughout Asia, daylily flower buds are regularly consumed after being cooked, while flowers may be eaten raw or cooked. Daylilies will spread and hold your slope together by means of rhizomes, which are thick underground stems, and by tuberous roots. The rhizomes may be boiled like potatoes and taste like sweet corn, while the fleshy, tuberous roots may be consumed raw or cooked. Be advised, however, that young green daylily shoots are toxic.

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