Questions From The Spring Into Joy Happy Hour

As always, I promised to answer the questions that we didn’t have time for in the latest happy hour. The answers are below. I also said that I would post the list of the perennials that I recommend all the time, and it is below along with a downloadable pdf that you can print out and bring into the store.

Q. Should I spray my peonies now so that the buds don’t turn black?

A. Peony bud blast (aka botrytis blight) is a fungal problem that can cause the buds on these perennials to turn black and die. Heartbreaking! It’s most common when the weather in April and May is cool and damp, which is pretty much the definition of spring on Cape Cod. You can spray with an organic fungicide such as Revitalize or Neem Max, but the key is to begin applications early in the spring as the stalks are coming up, and continue every week to ten days as the buds start to get larger. Usually once the buds are the size of a golf ball they are no longer vulnerable.

Q. Is there anything I should be doing for older rhodys right now?

A. Larger, older Rhododendrons are pretty self-sufficient, but if you’ve been removing leaves from underneath the plants, spreading an inch of compost over the area under the drip-line will help keep the soil amended. If you’ve mulched in the past or left oak leaves under the plants, that will be feeding the soil. If a soil test of the area shows that you need to fertilize, or if you haven’t fertilized in the past, a light application of Holly-tone can be beneficial. Spread the Holly-tone before you put down compost or mulch.

Q. Can we grow dahlias in containers?

A. The smaller varieties of dahlias do well in containers, but if you’re buying the larger, dinner-plate types you should plant those in the ground. Any dahlia tuber that is listed as staying under 3 feet tall would be fine in a larger pot. I’d recommend that the pot you use be at least 16 inches in diameter.

Q. Can you recommend some good perennials for Cape Cod?

A. Here is a list of great perennials for Cape Cod. This is in no way a list of all of the perennials that are nice and do well here, but rather a list of some that I recommend all the time because they are reliable and generally look good before and after flowering. At the bottom of this list is a link to the pdf you can print out and bring into the store.

 Sun to Part-Sun

Alchemilla mollis (lady’s mantle) – early summer – self-seeds

Amsonia hubrichtii (narrowleaf bluestar) – spring native

Asclepias tuberosa (butterfly weed) – summer native

Aurinia saxatilis (basket-of-gold) – spring

Baptisia australis (false indigo) – June native

Calamintha nepeta (lesser calamint) – summer into fall

Crocosmia (crocosmia ‘Lucifer’) – summer

Dendranthema (garden mum, fall daisies) – fall

Echinacea purpurea (coneflower) – summer native

(Hemerocallis) daylily – summer

Hibiscus (hardy hibiscus) – late summer native

Liatris (liatris or gayfeather) – summer native

Monarda (bee balm) – summer native

Nepeta (catmint) – early summer

Nipponanthemum nipponicum (Montauk daisy)

Peonia (peony) – early summer

Perovskia atriplicifolia (Russian Sage) – summer into fall

Phlox paniculata (summer phlox) – summer native

Phlox subulata (creeping phlox) – spring

Rudbeckia (black-eyed Susans) – summer native

Sedum (sedum ‘Autumn Joy’ and others) – late summer

Solidago (goldenrod) – late summer native

Stokesia laevis (stokes aster) – summer native

Symphyotrichum or Eurybia (perennial asters) – fall native

Shade to Part-Shade

Achillea millefolium (yarrow) summer native

Actaea simplex (bugbane) – late summer native (some have purple leaves)

Alchemilla mollis (lady’s mantle) – early summer – self-seeds

Athyrium felix-femina (lady fern) native

Chelone (turtlehead) – late summer – some are native

Crysogonum virginianum (green and gold) – spring native

Dicentra species (bleeding heart) – spring (D. eximia is native)

Epimedium (barrenwort) – spring – ‘Sulphureum’ is especially weed-smothering

Geranium macrorrhizum (bigroot cranesbill) – pt sun/shade – weed smothering

Hakonehloa macra (Japanese forest grass) – yellow varieties are colorful

Helleborus orientalis and niger (hellebores) – winter or spring

Heuchera (coral bells) – spring native colorful leaves

Hosta – summer – buy the size you want –  low ones make good groundcover

Lobeila cardinallis (cardinal flower) – summer – native okay in sun if soil is moist  

Tiarella (foam flower) – spring native

Download a copy of selected perennials for Cape Cod here.