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Episode 49 – The Self-Sow Show

Ground Breaking Banter - Rick

From the maple tree samaras (you may know them as “helicopters”) that whirl to the earth and plant themselves in your garden and lawn to the colorful lupines in your perennial garden, self-sowers are everywhere. However, the difference between a weed and what we’d consider a self-sower is that the self-sowing plants are beautiful or useful in some way, and generally much easier to manage than weeds are.

Self-sowing annuals are plants that will drop seed in your garden before they die and will germinate on their own the following year. So they return year after year like perennials, but from seeds, not from their roots.

One of the breeding goals for Proven Winners annuals is plants that don’t set seed. This isn’t just to prevent self-sowing (wanted or not), but because when an annual doesn’t set seed, it instead keeps flowering in an attempt to do so. That means more blooms and less work for you – no deadheading needed! One of the best-known examples of this is Supertunia Vista Bubblegum – people often remark on its ability to bloom all summer, and that’s because it is sterile.

A perfect example for me (having been in the industry 40+ years) are flats of sweet slyssum, called more often nowadays by its scientific name of Lobularia. When I first started out in the industry ‘Carpet of Snow’, ‘Royal Carpet’, and ‘Rosy O’Day’ were the alyssum of choice and we sold thousands of flats in early spring. They looked great when the weather was cool, then they’d peter out – but they would reseed prolifically. Today we have Proven Winners Snow Princess, a unique breakthrough in the genus for heat tolerance and extended season performance. This sterile lobularia is extremely vigorous, and because it puts no energy into setting seed it has an incredibly long bloom time. That makes the long-blooming, sterile Proven Winners varieties ideal for containers, and you can put the old fashioned ones in a vegetable, flower, or herb garden to re-seed and sustain pollinators.

Tall verbena (Verbena bonariensis) has long been a favorite self-sowing annual. Many people like it because it’s a “see-through” plant – its open branching structure helps it play nicely with other plants. If you’ve found the old type too aggressive for your taste, try Proven Winners Meteor Shower™ verbena. It has a denser, more vigorous growth habit which equates to more manageable and attractive plants as a flowering thriller in containers and massed in the landscape. And since the plants set little seed, it won’t spread. Heat and drought tolerance and deer resistance sweeten its appeal.

Rick’s Lim-A-Rick on the topic:

These plants! I do not know where from,
it must be my prolific green thumb,
The seedlings have become invasive
Their presence is pervasive
I’ll sell them for disposable income!

On to herbs – notably, borage. Borago officinalis is an annual herb that grows quickly but self-seeds prolifically so it continues to reappear year after year. Its beautiful blue flowers attract pollinators and have a light, sweet, delicious flavor, reminiscent of cucumbers. They are nice frozen into ice cubes for summer drinks, or sprinkled onto salads or anywhere you’d enjoy edible flowers. The hairy leaves are also edible, but are best when they are young.

When it comes to self-sowers, it’s nice to have useful plants, and borage isn’t your only choice. Under the right conditions, you can have dill, fennel, cilantro, parsley, chervil, arugula, and even oregano and thyme perpetuating themselves in the garden with no work from you. And anyone who has left a tomato or several to rot on the vine knows that they can come back for years – so can tomatillos, lettuce, and even greens like collards and spinach if you let them go to seed.

Looking to achieve a cottage garden look with some self-sowing flowers? Here are some to try:

California poppy
Bread poppy
Flax
Moss rose
Cleome
Nasturtiums
Calendula
Morning glory
Hollyhocks
Foxgloves

Why: Sunny Boulevard St. John’s wort (Hypericum kalmianum) is a plant that actually won’t self-seed, and that’s the point. For many people, when they hear “hypericum” or St. John’s wort, they immediately think “invasive!” because the species H. perforatum, also known as Klamath weed or common St. John’s wort, is an escaped species from Europe that is classified as a noxious weed in many states and provinces. However, it’s not wise to paint all plants called hypericum or St. John’s wort with the same brush, because we also have several native species of Hypericum that make excellent garden and landscape plant for its good looks and value to pollinators. The species of Sunny Boulevard, Hypericum kalmianum, is one of those. Also worth noting is that it is a shrubby plant, not a herbaceous one like the invasive species.

And it is a magnificent plant that is very much worth growing if you have a sunny spot. It naturally grows with a tidy, rounded habit, reaching 2-3′ tall and wide. In summer, it is covered in hundreds of yellow sunburst flowers – each bloom sports a mantle of fluffy yellow anthers that make it look almost fake. They contrast nicely with the blue-green foliage and attract native and honeybees. What’s more is that Sunny Boulevard St. John’s wort won a blue ribbon award from the University of California-Davis drought trials. High praise, indeed, to win an award for performance in drought in a place like California!

Who: Sunny Boulevard hypericum was selected right here in West Michigan at the Proven Winners ColorChoice Shrubs HQ. 

How to Grow: It will probably come as no surprise that with a name like Sunny Boulevard, this is a sun-loving plant and should only be planted in spots that get at least six hours of bright sun each day. It is quite drought tolerant and will continue looking good even under extreme conditions, but we recommend regular watering for its first year or two to get it established – that will make it far better equipped to deal with future challenges. It blooms on new wood so can be pruned in spring; it can also be trimmed if desired. It naturally grows into a rounded shape but you can trim it to impose an even tighter shape if that’s a look you like. 

If you’d like to add Sunny Boulevard St. John’s Wort – or any of the 320+ Proven Winners ColorChoice Shrubs – to your garden or landscape, you’ll find a list of local retailers here

Gardening Mail Bag - Stacey

One of the advantages to growing heirloom flowers and vegetables is that they “come true” from seed – in other words, the offspring produced by the seed will pretty much exactly resemble the parent plant. This means seed can be saved year to year and you’ll continue to get good results and the same tomatoes that look and taste like you expect them to. Saving seed on tomatoes is pretty simple, but it is generally recommended that you rot them a bit first to dissolve any gel on the seed that may prevent germination. To do this, squeeze the seeds out of a very ripe tomato and rinse off as much tomato flesh as you can. Put them in a cup with about a half cup of water and let it sit in a warm, bright spot for about five days. Mold will form, but that’s good! Skim it off, stir the seeds, pour off the water, and rinse. Do this a couple more times to remove any tomato tissue, then discard any seeds that float – only those that have sunk to the bottom are viable. Let these dry on a plate (Rick’s pick, because the seeds can stick to paper towel), then store in a cool, dry, dark spot until next season. 

Saving the lettuce seed is even easier – just let it elongate, which indicates it is going to flower, then let the flowers develop into seeds. Let the seedpods become dry and brown, then collect or shake them into a paper bag. Store them, like all seed, in a cool, dark, dry spot until you sow them next season.

We love the limerick, Shirley – thanks! ‘Annabelle’ hydrangea will flop naturally – it’s just what it does. That said, there are a few things that you can do to minimize the flopping and get the strongest possible stems. First, do not cut it back to the ground. This is common practice for many people who grow ‘Annabelle’ but is not recommended because it never gives the plant a chance to develop sturdy, woody stems that will be much more supportive than herbaceous growth. Instead, cut it back by about one-third its total height each year, removing any thin side branches at that same time as well. Second, don’t grow it in too much shade – that will cause the stems to elongate, reaching for the light, and become weak. Try to give it at least a few hours of sun, ideally in the morning in hotter areas. Third, avoid overfertilizing. Excessive fertilizer – especially combine with large quantities of water – can push soft growth quickly, resulting in weakness. Once a year in early spring is perfectly fine, as is up to once a month from early spring through late July. Opt for granular (not liquid) fertilizers formulated for trees and shrubs.

Finally, consider Incrediball hydrangea instead. We developed it specifically to have everything everyone loves about ‘Annabelle’ but without the weak, floppy stems. Not only did we get that, we also got much larger blooms! Of course, for best results, you’d still want to follow the steps we outlined above. However, whereas ‘Annabelle’ will likely still show some stem weakness even if you do all that, Incrediball should hold up, especially once your plant has gotten established. 

You make a great point here, Amy – some plants do just kind of go out of style, and I think that is largely the case with mock orange (Philadelphus coronarius). It is indeed considered old-fashioned, but I don’t think that’s the issue – more likely it’s because all of the older varieties of mock orange are HUGE – like 12′ tall and wide. Not very compatible with most homes and yards these days. Also, though their bloom and fragrance is genuinely sublime, it has typically been short-lived, so it’s a lot of real estate to give up to a plant that only gives you a fairly fleeting moment of show. We are trying to change all that with our Illuminati series of mock orange. We are looking at unique new habits that are much easier to work into the garden, like Illuminati Tower, as well as plants with foliage interest, like Illuminati Sparks. We’re hopefully these plants will spark a renewal of interest in this beautiful native shrub!

Do you have a question for us? We’re happy to help! E-mail us or use the contact tab above.

Branching News - Rick

On this episode, we interview Andrew Bunting, Vice President of Horticulture at the Pennsylvania Horticulture Society. Andrew received his B.S. in Plant and Soil Science from Southern Illinois University. Prior to arriving at PHS, Andrew worked at the Chicago Botanic Garden, Chanticleer Garden, and the Scott Arboretum for a tenure of 27 years. He has received the American Public Gardens Association’s Professional Citation, Chanticleer Scholarship in Professional Development, and the Certificate of Merit from the Pennsylvania Horticultural Society. He also serves on the Board of Magnolia Society International. Andrew published his first book in 2015, “The Plant Lover’s Guide to Magnolias.” We interview Andrew about PHS and its signature annual event: The Philadelphia Flower Show.

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