Question: We’re trying to design a low-water 2,500-square-foot back yard with a big pine tree overhead. We’ve looked at some designs but they all use crushed rock or gravel or bark, which I don’t think will work for us since needles will get into stones or gravel or bark and be really hard to clean out.
Blowing and raking won’t get them out and would disturb the stones or gravel or bark severely every time.
Any idea how to approach this? I’ve been trying to figure out a way to work with the pine needles rather than fight them, but no luck so far.
– Nick Kurek, Granada Hills
Answer: You may want to consider decomposed granite (DG) as a base material or ground cover for your pine needle garden. Decomposed granite is a buff colored, coarse textured, gritty substance that compacts into a hard surface. You can use it for pathways, but you can also plant in it.
You can rake or blow needles off decomposed granite without scattering or degrading it. You will need a two inch layer compacted with a sod roller (available at rental yards and some nurseries), to create the desired effect.
When considering a large outdoor space such as yours, it is prudent to divide it with paths or walkways. In this manner, the planting areas that are created between the criss-crossing walkways are easier to manage. It also makes it easier to be experimental, as you can try a different selection of plants in each walkway defined planter bed.
You are always a beginner in the garden, especially when planting under pines, since the amount of light available will depend on tree height and branch density. It would be wise to plant a single specimen of a number of different species to see which work best for you before committing to a large scale planting of one type of plant or another.
Pine needles acidify the soil, a good thing in Southern California since most plants prefer a somewhat acidic soil pH and our soil pH is alkaline. However, the benefit of soil acidification is more than counterbalanced by the aggressive roots of a pine tree, which take up most of the water and minerals in the vicinity.
Amongst tall trees, pines have unusually shallow root systems and the soil underneath them is notoriously dry.
Moneywort Grows Under Mature Pine Trees
Upon receiving your e-mail, I decided to visit the Tarzana Community and Cultural Center garden on the corner of Vanalden Avenue and Ventura Boulevard since I was familiar with the pine trees that dominate the grounds of that property. I was pleasantly surprised to see a lush expanse of moneywort (Lysimachia nummularia) growing beneath the pines. Moneywort, so-called because of its circular leaves that resemble coins, is known as favoring moist soil, yet the only evidence of an irrigation system in the moneywort section of the pine tree garden was a nearby hose. Given the deep shade cast by the pines overhead, I doubt that much water was being applied to keep the ground sufficiently hydrated for moneywort to grow.
Just because a plant prefers moist soil does not mean it needs to be heavily watered, as long as there is sufficient shade or mulch to keep the roots cool. Here, the dense growth of the moneywort provided a living mulch, minimizing evaporative water loss from the soil.
Mediterranean Fan Palm and Sago Palm Grow Under Mature Pine Trees
Other plants growing well under the Tarzana pines include Mediterranean fan palm (Chamaerops humilis), sago palm (Cycas revoluta), bronze dracaena (Cordyline australis ‘Atropurpurea’), and the largest orange Jessamine (Murraya paniculata) shrub, measuring seven feet tall and wide, that I had ever seen.
Orange jessamine is in the citrus family and, in the manner of orange trees, produces perfumed blossoms.
Ceanothus Grows Under Deodar Cedar
I recently saw some extremely healthy California lilacs or ceanothus (see-a-NO-thus) shrubs growing under a deodar cedar, which would suggest cenothus compatibility with pine since cedar and pine have similar cultural requirements.
Ceanothus is drought tolerant, requiring little, if any water, once established.
Nitrogen-fixing bacteria live in symbiosis with ceanothus roots, so this species never needs fertilization and has been known to die prematurely when fertilized.
It is a fact that certain ceanothus, as well manzanita (Arctostaphylos) species, for that matter, are found growing in red fir and yellow pine forest ecosystems, which suggest compatibility with pine trees. You might try planting one ceanothus and one manzanita under your pine and see what happens.
I have had success growing Australian rosemary (Westringia fruticosa) under pines so you might plant one of them as well, either a common variety or a dwarf, as part of your pine tree garden experiment. Columbines (Aquilegia), those colorful annual to perennial favorites, with the dove tail flower appendages and lacy foliage, also grow well under pines.
If you do plant in the ground under pine trees, you will want to amend the soil conscientiously and create raised beds to improve drainage. An alternative to planting in the ground is container planting. This allows you to bring in almost any kind of plant that grows in the shade, including fern and succulent selections, without the responsibility of the laborious task of building raised beds. Under the pines at the Tarzana Community Center garden, blue and red succulents are growing in an oversized oyster shell container.
At the rear of the Tarzana garden, facing an alley, a spectacular wisteria vine is in full bloom. The key to coaxing a heavy bloom from wisteria is summer pruning. You should cut back this vine once a month between June and September, much like you would prune a hedge.
Wisteria vines, like apple trees, produce flowers on spurs, stubby stems with corpulent flower buds. The more often you summer prune rampantly growing wisteria shoots, the more flower buds you create on spurs, ensuring heavy bloom the following spring.
TIP OF THE WEEK
The most brilliantly flowering azalea I have seen this spring, a solid sphere of pink, is growing in front of an apartment building on the south side of Moorpark Street between Dixie Canyon and Greenbush Avenue in Sherman Oaks. This phenomenon proves that plants have minds of their own and, time and again, defy commonly accepted wisdom concerning their care. You would think that an azalea would flounder if planted in a lawn under three liquidambar trees since its shallow, delicate roots could never compete with the turf and tree roots. But there it is, a lesson in the oftentimes contrarian success of plants and a call to be bold and experimental in the garden.