Notes on Butterfly Plants

We like to see butterflies in our gardens, that is some butterflies, particularly bright, colorful butterflies like the monarch. It’s the caterpillars that we don’t like, the ones that feed on our plants. Luckily for the monarch, the caterpillar stage only feed on weeds, that is, they feed on milkweed, typically common milkweed (Asclepias syriaca), a plant that’s essential to the survival of the monarch butterfly.

It’s not a plant that’s typically grown in suburban gardens, although it would help reduce the decline of the monarch if there was a milkweed plant in every backyard. Since it’s not considered particularly attractive as an ornamental plant, it’s unlikely to happen, but A. syriaca is only one of a number of milkweed species that appeal to the monarch.

In my garden, I have swamp milkweed, which has narrower leaves than common milkweed and grows to about a meter and a half with lots of pink flowers. This species favours medium to wet soils and is well suited to a rain garden or low area, although it wasn’t troubled by last summer’s long dry spell in my garden.

I grew another milkweed species a couple of years back from seed, Asclepias curassavica, a tropical milkweed commonly known as blood flower. This was a pretty plant with showy red/orange flowers and a nice addition to the garden at the time, but it’s not hardy in this area, dying completely over winter. When grown in warmer regions to the south where it can be invasive, questions have been raised about its impact on the monarch. It can act as a host plant, but it’s believed the growth habit of producing new foliage throughout fall and winter can result in continuous breeding on the same plants, ultimately affecting the natural migration patterns of the monarch. They don’t feel the need to leave for Mexico as they should.

There have been calls for eradication of tropical milkweed, but research is still underway to determine the impact of removing a plant that regardless, does provide essential food. Since tropical milkweed can’t survive beyond fall, it’s presumably an acceptable annual plant for our gardens in the north.

Better still, there is another milkweed species we can grow that will attract and feed monarch butterflies. It’s not a major host plant for the monarch larvae, but the flowers provide essential nectar for the adults and it also attracts other butterflies, hence its common name, butterfly weed (can we stop calling them weeds?).

This species is Asclepius tuberosa and like the tropical milkweed, it has similar orange/red flowers. Better still it is hardy to zone 3, making it tough enough to easily survive winter here. Plant in full sun and it will grow in a bushy shape to about knee height. Once established this plant is drought tolerant thanks to a deep taproot. A deep tap root means it isn’t easily moved, so choose carefully when deciding where to place it. This is such a well-respected plant that the Perennial Plant association has chosen it as the 2017 Perennial Plant of the Year.

If you’d like to learn more about attracting monarchs and other butterflies into your garden, there’s an excellent book by local author Thelma Beaubien. It’s called Gardening for Butterflies: Attracting, rescuing and raising butterflies.

Two Four Time

This is it, the traditional spring planting time in this part of the world, but if you don’t get around to planting because of other exciting two four stuff, don’t worry. There’s plenty of time left for planting.

Once upon a time, most annuals were sold in tiny cell packs and it created an urgency to get them into the garden early to ensure they started growing, even though they wouldn’t budge until the soil warmed up. Now, with a trend towards larger, more mature plants in individual pots, timing is less critical.

Whether you plant this weekend or wait until early June, there is one thing that will help your flowers and vegetables when they have to face blazing hot summer days, and that’s mulch. In nature, there’s always mulch on the surface of the soil, usually in the form of a leafy layer.

Plants expect to be surrounded by mulch; bare soil is not normal. Covering soil conserves moisture, keeps down weeds, and if organic, it slowly adds nutrients to the soil as it breaks down. Over the years, I’ve used a variety of materials as mulch: leaves, manure, mushroom compost, wood chips, straw, shredded bark, and cocoa bean husks.

Anything that covers the soil surface while allowing moisture to penetrate does the trick. I’ll even use clippings from evergreen shrubs, and I always make use of my ornamental grasses crop. It does a fine job in the veggie garden. As they break down, they all help feed the soil, which is so important.

Wood chips or shredded bark are popular, especially on flower beds in front yard gardens. A few bags may be all you need, but if you’re a heavy user, consider ordering in bulk. When spreading mulch from four to eight centimetres deep, which is usually sufficient, a big bag will go a long way.

There has been a concern that as wood based mulches break down, they can deplete the nitrogen in the soil, but this only occurs in the uppermost layer and isn’t as much of a problem as was once believed.

As mulch slowly decomposes, nutrients and organic matter are absorbed, feeding the organisms in the soil. This is a natural process, but it is far more complex than it appears, especially to anyone who dismisses soil as dirt — dirt is what you get on your pants after sitting in soil.

Soil is not inert brown stuff, devoid of life, although it may well be if it’s been regularly doused with chemical fertilizers. It is teaming with an incredible number of life forms, each of which has a role to play. Worms and soil insects are easy to spot, but it’s what we don’t see that’s tremendously important:  microscopic insects, fungi, bacteria (good and bad) all play a role. They form symbiotic relationships with each other and with the roots of plants and trees, processing organic matter and minerals, converting them into nutrients in a form that plants can use.

Healthy soil is essential, the source of the life above ground that we can see. As you plant like crazy over the next few weeks, give a thought to what’s going on below — and spread the mulch.