Alyssum spinosum is my favorite plant in the garden, this week...

Despite my love of rhododendrons and lush shade gardens, or perhaps because of it, I try to plant mostly drought-tolerant plants in sunny areas of the garden. One such plant that I've really enjoyed for years is Alyssum spinosum, or spiny alyssum (that should be an easy one to remember). This is a hardy, shrubby perennial and is a true member of the genus Alyssum, unlike the annual sweet alyssum, or Lobularia maritima, though they are related.

In winter and early spring, the evergreen foliage is an attractive but not especially note-worthy grey-green. It forms dense mounds that billow over rocks, contouring slightly to the shape of the stones. The structure of spiny stems and leaves is intricate and interesting to study. Here you can see it in early May opening its first flowers. The bare, green spines are actually the bases of the flower stalks, providing protection for both the developing flowers and the new growth later on. Most of the new growth will actually sprout from the junctions of these spiny spur branches. This becomes important knowledge for cleaning up after it blooms.

In full bloom, the mounds can be almost smothered in white to purple flowers that have that wonderful alyssum scent similar to honey. This mound (below) is actually two plants. The pink one on the left is in full bloom while the larger white one is a bit past its peak. I've had a handful of seedlings appear during the 6 or 7 years since planting the original two plants, which I believe were also seed-propagated, so there is some variation in bloom time and color, though all the plants so far are quite uniform vegetatively. These two I believe are the original plants. The white seems to be more vigorous, but all seedlings have had blooms in various shades of pink, so as usual the white flower is recessive and the pinks will win out.

Two of the first seedlings from the original two plants, in two different shades of pink.

A darker pink seedling, though still pretty light, has slight purple tones.

A lighter pink bloom.

The flowers are nice, and the fragrance is wonderful if you go to the trouble of bending down to its level or you can grow it in a raised area or the top of a wall. My favorite season for this plant is in summer, when the foliage changes to a beautiful silvery blue-grey and the old flower stems provide an array of tan spines with the delicate, translucent remnants of the slightly spring-loaded seed capsules. These old flower stems, along with stiff leafless spur branches, provide the spines that give this plant its name and its deer-resistance. In fact, I've never seen deer damage on these plants. In my garden, that is REALLY saying something!

Most people would probably be inclined to tidy up the plant by removing the old flower stems. If you grow this and decide to do so, only lightly trim off the dead flower stems. Cutting too far back will remove the buds from which most of the new growth comes, causing the plant to sulk or even die back a little, and it will be thin in the cut areas for a while. Far better to enjoy the contrast between the almost golden stems and the silver foliage. This is a very low maintenance plant. It doesn't even want you to dead head it! And don't worry. I know I said the seed capsules have a bit of a spring-loaded nature, but I have only ever gotten 2 or 3 new seedlings per year, if any.

Spiny alyssum also pairs wonderfully with dark foliage, like this black mondo grass.

 I used to be a pretty obsessive compulsive gardener, but I've since learned to relax a bit more. When I first saw the old, brown flower stalks I itched to remove them and ended up cutting into the plant trying to get rid of every little bit. I didn't realize that I was removing the defensive spines of the plant or that I was actually inhibiting the plants growth. New growth sprouts thickly from the lower parts of the flower stems, so I was removing the main points of new growth in my desire for a neat and tidy plant. Luckily after a couple years it filled back in to a nice mound. Now I enjoy the contrast between the leaves and the old flower stems, especially the almost diaphanous remnants of the seed capsules.

 Like tiny hand mirrors arranged around the central axis of the flower stem, the remnants of the seed capsules are intricate and beautiful to look at. If you are a little obsessive, you can brush your hand lightly over the plants when the seed capsules turn brown, causing the brown coverings to fall off and revealing the translucent membranes within. The old flower stalks will eventually be hidden by the new growth.

The stats on Alyssum spinosum:

• Little consensus on hardiness, with lowest zones from 3a to 8b and even less regarding upper zone limits. Definitely hardy to USDA zone 7b and probably much colder. Seems to be more common in the UK than in the US, where hardiness is often rated as tender, half-hardy, or fully hardy. (Spiny allysum is fully hardy in the UK, but that isn't much help for most the US, not that I'm annoyed by their poor hardiness descriptions or anything. At least give a rating of H1-5 like the RHS does. The RHS rates it as hardy to H5, -15C or 5F. OK, rant over.) 
• Full sun to afternoon shade, prefers as much sun as possible
• Drought tolerant in a fairly dry southwest WA garden
• Deer and rabbit resistant
• Very low maintenance, old flower spikes can be lightly sheared to expedite covering up by new foliage

This little sub-shrub is a great addition to rock gardens, xeric gardens, and anywhere deer or rabbits are a problem. Spiny alyssum is a great example of a dynamic plant, changing throughout the seasons. It's also a practical, low-maintenance plant that looks and grows best if allowed to be a little wild.

Be sure to click over to Danger Garden, the host for the favorite plant of the week meme, to see the favorites of Danger and other bloggers this week.