Designing with Bulbs

We’ve all read some great articles about designing with bulbs (and corms) so why not keep the discussion going? Designing with bulbs can be daunting. Visiting the botanic gardens in spring nearly blinds us with the glory of huge swaths of spring bulbs. Vast beds of daffodils, crocus and tulips are the sure sign that spring has sprung. A bed of crocus dusted with snow is an iconic image of early spring. Now let’s focus our attention on some other aspects of designing with bulbs, year-round interest and designing to specific bloom heights.

5177_WPFL_Eremurus-himalaicus-WMC_001Dahlia 'XXL Veracruz' AZTEC

The opportunities presented by designing with bulbs can be taken advantage of year-round with a little planning and great execution. Gladiolus and Dahlias can bring in a huge color punch during the mid-summer to late summer in warmer climates and similarly Allium and Autumn Crocus in colder climates. Similarly, lilies can provide a tremendous amount of foliar interest in the early summer months and then finish the season off with splendid color in late summer and even through the fall. The first step is to sort through the vast array of choices in bulbs and corms and remember what you are trying to achieve. Here a sampling of a season-long list for a garden in zone 6a, that’s scented, and attracts bees, hummingbirds, and butterflies. This short list from The Plantium yields plenty of choices to keep you thinking about designing with bulbs all season long! There are so many more to choose from!

Bulb Flowering Season

The next consideration is careful planning around bloom height. This same list now includes plant (foliar) height vs. actual bloom height. Not planning for the bloom height of late blooming bulbs is a common mistake. Some height variations will be minimal but some can be more than a foot or even up to 4’! Check out the Foxtail Lily. Many of these bulbs are not known for lush foliage so you can place them further back in the garden (than you might normally based solely on foliar height) with other perennials or shrubs around them. This leaves their bloom to surprise us when the time is right!

Bulb Flower Heights

Planting Under Evergreens

OK, technically this is a designing and planting UNDER evergreens (not WITH evergreens) but let’s roll with it. “Why won’t anything grow under this spruce!” Try planting under a pine, fir, or any other large needled evergreen, and you get a universal refrain echoed by professionals and garden enthusiasts all over the country. This blog explores the reasons plants won’t grow under your conifers, and what you can do to create a beautiful landscape when planting under and around mature evergreens.

First we’ll explore the most popular assumption as to why nothing will grow: “The soil is too acidic (or toxic?)!”

Let’s put toxic to bed right now. It is flat out not true. A myth. Now many others believe conifers acidify the soil around them through needle drop to the point where no other plants will thrive. It is true that the soil around conifers is often acidic. As a general rule, conifers prefer more acidic soils, and if you see a large, healthy needled evergreen you can usually assume some level of soil acidity. It is also true that, over long periods of time, some species of conifers acidify the soil around them through needle drop especially if the pine needle duff is allowed to decompose and is not cleared out each spring.

Planting under evergreens bares all

A natural pine duff layer

But let’s take a moment to review the pH requirement of many evergreens in comparison to the pH requirements of most ornamental landscape plants. Although they can often withstand more acidic soil, the ideal pH for Norway spruce, Fraser fir, Canaan fir, Scotch pine, White pine, Douglas fir, Blue spruce, and Concolor fir is between 5.5 to 6.5. This jives fairly well with the average range of 5.8 to 7.0 for most ornamental landscape plants!

Here, just as in the rest of life, it is important to never assume. Always test your soil before pinning the blame on low pH! You can make some amendments to the soil to bring the pH up a little while still maintaining it in the acidic range that your evergreens will love.

Regardless of soil pH, there are likely three other tricky factors at play under your tree: Shade (possibly very deep shade), dry conditions, and nutrients. The dry conditions are due to two factors. First, the dense canopy creating the shade also prevents much water from reaching the ground directly under the tree. Second, up to 75% of feeder roots for the tree are in the top 12” of soil. These roots are competing intensely with any other plants for available moisture and nutrients.

So to counter these challenges, you must create the dreaded DRY SHADE GARDEN! Any internet search will reveal that dry shade garden plants are about as easy to find as the holy grail.

So before you charge ahead, ask yourself one more time: do you REALLY need to plant under that evergreen, or can you plant around it and neatly mulch the area directly under the tree? If you decide you really must plant, get ready to tackle the last hurdle: extensive surface roots!

The surface roots from your tree can make it very difficult to dig in new plants. Adding planting soil on top of tree roots can kill a tree, so the best bet is to buy the smallest plants available and dig them in individually around the roots. Apply 2” or so of mulch (never more than 4”, as deeper mulch could be detrimental to the tree), and water your new plants very well at least for the first growing season, or until it looks like they are holding their own. In drier climates of the country you can probably count on ALWAYS having to maintain irrigation under the evergreen tree to make sure even the dry shade plants thrive. It is a delicate balance, however, as overwatering in the shade and developing fungus and root rot issues is a common misstep.

Finally, this still does not tackle your final challenge of nutrient competition. A large, healthy evergreen is sucking up a significant amount of the nutrients in the soil. By committing to planting directly under the tree you are committing to a constant refresh of the plants every few years as they run low on nutrients and cannot compete with the large tree OR you are committing to a CONSISTENT regimen of soil amendments. Either way, these gardens will require serious nurturing.

The Plantium is a great resource to quickly spec dry shade plants for your project. Another way is to just head out to the woods and check out the natural understory in your area! Lastly, botanic gardens and the agricultural extension for your area are great sources for dry shade plant recommendations.

Conquering planting under evergreens

What success looks like!

Designing with Cactus

What is a Cactus?

Many people, even those who consider themselves familiar with arid plants, get confused when it comes to what really constitutes a cactus. Isn’t it basically anything spikey that grows in dry climates? No! A cactus is, in fact, a very specific thing.

Cacti are members of the family Cactaceae. There are approximately 1,800 species of cactus.

Two specific things set cacti apart from other plants:

  • Not all cacti have spines when they mature, but a great way of distinguishing a spiney cactus from other spikey plants in the field is the presence of “areoles,” little bumps on the plant from which clusters of spines grow. If the spines on the plant are not growing in clusters out of these bumps it’s not a cactus!

Cactus aerole

  • All cacti also have a specific flower structure. Though the flower of each cactus species may be very different, all cactus flowers have many tepals (a term used when the sepals of a flower are indistinguishable from the petals) that are somewhat fused; hundreds of stamens; and many-lobed stigmas.

Yellow prickly pear cactus flower

Designing with Cacti

As a group, cacti are drought tolerant and are a great option for any water-conscious landscape. But xeric gardens aren’t the only ones that can benefit from the use of cactus! Their frequently strong sculptural or geometric forms and punchy colors can add punctuation to any landscape design, as long as the growing conditions are right.

Cacti with upright or twisting forms are popular for use against a striking backdrop such as a richly-colored wall, or for their silhouette against a vista. They can also be grouped together for great large-scale textural effects, or consider pairing their chunky forms with something soft such as Mexican Feather Grass (Nassella tenuissima) for inviting contrast. Barrel cacti are perfect for creating rhythm and reinforcing patterns in design, and the bold textures and colors of pad cacti (Opuntia) provide great backdrops or focal points in the landscape.

Agaves, other succulents, and grasses are great design companions, but cacti can really be added to any composition with complimentary leaf colors, contrasting textures, and similar environmental requirements.

Most cacti are very sensitive to over-watering, so make sure the soil is very well drained, and the other plants in your design have compatible water use requirements. Use The Plantium to easily find great cacti and appropriate design companions for your next project!

Fun Facts about Cacti

  • All cacti are succulent, but not all succulents are cacti!
  • All cacti are native to the Americas, though they have spread around the world post-colonization.
  • Although they are typically slow growers, cacti are very successful in arid climates, so much so that in certain countries like Australia many cacti are considered noxious weeds.
  • Cacti grow in a wide variety of places, though mostly in habitats that experience some drought. People associate cacti with hot climates, but there are many species that are hardy to -30 deg. F and lower!
  • Cacti come in a wild variety of shapes, sizes, and forms, from the stereotypical Saguaro, barrel, and prickly pear, to the Rose Cactus (Pereskia grandifolia) which looks like a tree or shrub at first glance.
  • Most cacti don’t have true leaves, instead performing photosynthesis in their modified stems. However some cacti, like the rose cactus, can be very leafy!