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Tulsa Gardens Now!

June 2010

Summer is here, and well before the first of June this year. Planting can continue but be careful. As it gets hotter, perennials have a harder time getting established, and woodies can struggle too. If planting in full sun, consider temporary shading on newly planted perennials. Also be sure to cut foliage back to help with transplant shock (if dividing). Use caution on watering. A droopy perennial or shrub may be growing in saturated soil, but just unable to keep its top hydrated with its small root system. Check the soil before adding water, and again, consider shading until your young plant begins to take hold and fend for itself.

Try to concentrate on perennials/annuals that don’t mind heat. These include dahlias, mums, summer phlox, etc. Early spring blooming perennials prefer the cooler temperatures of fall.

Controlling Plant Growth

June is the month for finishing up the deadheading and shearing back of most early spring blooming perennials. Shearing back by 1/2 will neaten up foliage and prevent leggy growth. Plants included in this group are Phlox subulata (creeping phlox), Iberis (candytuft), Dianthus ‘Star Series’, Dianthus barbatus (Sweet William), Veronica ‘Waterperry Blue’, Veronica ‘Georgia Blue’, Phlox divaricata (woodland phlox)and their companions.

Stake plants that might need a helping hand.

Continue to weed and be sure to mulch after weeding.

Spray for bagworms now…the worms are there even if the bags are not.

With all the rain and cloudy weather we have had in the spring and up until mid-May, some plants may have had a growth spurt and become leggy. Shear back to basal growth or cut back by ½ to reduce height and stop floppiness.

Nepeta varieties respond quickly to extra moisture. Consider cutting the foliage back even if it is still blooming; cut it back to basal foliage and end up with a compact plant for the rest of summer.

Deadhead peonies by removing the spent blossom to first or second leaf below it.

Deadhead Amsonia at this time. On taller varieties it is sometimes necessary to trim the foliage back by 1/3 or so to prevent the foliage from lying over on other perennials.

Deadhead Brunnera, removing the old flower stems below foliage. This will be the last deadheading of the season.

Deadhead bearded iris, Iris pseudacorus and Iris tectorum (Japanese roof iris), removing flower stems as low as possible.

Dicentra eximia (everblooming bleedingheart) benefits from deadheading this month. Bloom will be sporadic for rest of the year.

Old-fashioned bleedingheart will go dormant in the next few months. Remove yellowing leaves as needed until it is completely dormant. Dividing either now or in the fall is possible.

Cut back and remove the dying foliage of Lycorus radiata and L. squamigera, the surprise spider lilies and naked lady lilies. Mark with colored gravel to help remind yourself that there are bulbs in the area. Blooms will appear in August and September.

Deadhead Gaillardia, all varieties, as needed. Use the 7-day rule, removing any flower that will not last 7 days. This schedule will keep the plant looking nice all blooming season. This is also a plant that will continue to bloom even without deadheading but at some point only spent flowers will remain. This usually happens sometime in August or early September. Cut the plant back by half at that time. It will rebloom in 4 weeks.

Deadhead as needed Salvia ‘May Night’; and Veronica ‘Sunny Border Blue’.

Aquilegia (columbine) are on the downside of blooming. Deadhead to a lateral (side) bud. If the stem shows no more buds, remove the bloom stem down into foliage. The foliage needs to be looked after now that it is turning hot. Leaf miner and spider mites will begin to set in. When the trails of the leaf miner can be seen on the leaves the sooner they are removed from the plant and the garden the better. If the plant is overwhelmed with leaf miner, cut the entire foliage clump down. It will regrow. Clean up the area around troubled columbine, removing all dead or diseased foliage.

Tiarella varieties are finishing up blooming. Remove the spent bloom stems for a neater look.

Hardy geraniums (cranesbill)that are finishing blooming can be deadheaded now. This is another plant that will respond quickly to cloudy, rainy weather by becoming leggy and floppy. Trim the foliage back to encourage new growth that will be more compact.

Penstemon digitalis ‘Husker Red’ will need deadheading soon. Use the 80/20 rule. If 80% of flowers on stem are spent go ahead and remove entire flower head down to basal foliage (unless you prefer reseeding in the garden).

To control height on perennials:

• Rudbeckia ‘Herbstonne’ can be cut down by half for height control.
• Eupatorium ‘Joe Pye Weed’, hardy ageratum and E. rugosum ‘Chocolate’ can all be cut down by half for height control this month.
• Others that can be cut back by half for height control are Salvia leucantha, Salvia ‘Black and Blue’;, Helianthus, and Heliopsis. Some of these varieties really stretched due to the extra moisture we had in May and they may flop. Cutting back by half can delay bloom but will make them stronger. Not cutting back, they may require staking. Your choice: stake or delay bloom. The delay in bloom may be 3 weeks, mostly for Salvia ‘Black and Blue’ and Heliopsis since they already have bud set.
• Cut the foliage back by half on Sedum ‘Autumn Joy; (and others similar in growth).
• Tricyrtis hirta (toad lily) and Solidago ‘Fireworks’ can be cut back by half in June if shorter plants are preferred when they bloom in the fall.

To deal with the rot problems due to humid, rainy weather:

• Thymes and Oreganos can be cut back, removing any black or rotting foliage that began during rainy periods. Cut back old flower heads to neaten plant and encourage branching and compactness
• Another plant that resents cloudy and humid weather is the Artemisia ‘Silver Mound’. If the foliage is starting to part or turn black, trim it back by half. It is very important for this foliage to dry by night time.

Vegetable Garden

The vegetable gardens are getting into full swing now, with the leaf crops giving way to the hot season crops. The European Cabbage Moths are busy dancing over your cole crops laying eggs. Pretty as this is, it will lead to green lace instead of vegetables as the eggs hatch into tiny green worms that will eat vast holes in your plants. Bacillus thuringiensis, more commonly Bt, works like a charm on eradicating these fearsome babies, and is safe for non-caterpillar creatures. Cole crops include cabbages and their kind, radishes, mustards, and turnips.

Vining crops will begin to run soon. Be prepared to trellis those that you will be growing vertically, and get mulch into place for the ground runners. These include squash, melons, gourds,and cucmbers. Although tomatoes don’t “run” in the same way that the cucurbits do, they will need corralling now before they get too big to manage.

Watering is crucial during the hot days, and it is important to do it carefully. You want to give the plants just exactly the amount they need, no more, and you want the foliage to dry before nightfall to avoid fungal diseases. It sounds simple, BUT…With the onset of heat it is time to watch for spider mites. When you see spider mites on your veggies, the best controls are to keep the foliage humid, especially in the heat of late afternoon. A good strong stream of water disrupts the mites and the humidity discourages their return. As you can imagine, this is a pretty time management problem. Do your best, and be sure that you will get it wrong at some point! Gardening is not for the faint of heart.

And finally, with mowing weather upon us comes the racket of the string trimmer. Be very firm with whoever is using a string trimmer near you plants, including trees. String trimmers will kill trees as surely as ice and forest fires, and they are much more prevalent.