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Gardeners Grow Together Week 14, April, 2021: Half-Hardy Annuals

Welcome to my special gardening page for those of you who like to garden yourselves! Each week, I will make suggestions as to what gardening tasks we need to do every week during the growing season. It will help keep you on track--as well as myself!

To keep things simple, I am using the year's weekly number, Week #1 through #52 (example: the week of January 1 is Week #1), instead of specific dates.

So, come on! Let's get our hands dirty!


Week 14:

Starting Half-Hardy Annuals from seed and Potting-on Tomatoes

Half-Hardy Annuals

Potting-on Tomatoes


Annual Plants

Annual plants are plants that grow from seed to flower in one season, then they set seed and die.

Within the category of Annuals, there are three types:

Hardy Annual: Seeds that require a prolonged period of freezing before they will germinate. (See my blog on winter sowing.)

Half-Hardy Annual: Seeds and plants that require cool weather to germinate and bloom well.

Tender Annual: Seeds and plants that will not tolerate any freezing or frost at all.

Half-Hardy Annuals

This week we will concentrate on starting Half-Hardy Annuals, which include: Cosmos, Cleome, Petunia, Nasturtium, Straw Flower, Baby’s Breath, and Forget-me-nots, just to name a few.


Half-hardy annuals prefer to grow in cooler temperatures. The seeds can tolerate some frost, but the plants usually cannot, or are at least damaged by frost. The seeds, however, do not require the hard frost nor warm soil temperatures to germinate.


Some plants will flower heavily early in the season, then peter out as the temps rise; others will bloom in the spring, wane during the hottest months, then surge again in the fall; others will bloom and bloom, all season long.

Sowing the seeds

Half-hardy seeds can be direct sown out in the garden as soon as the soil can be worked. Starting indoors now, however, will give you the earliest blooms. If starting indoors, plant your seeds six to eight weeks before the last frost date in your area. Here in Colorado, in Zone 5b, our last frost date is generally May 15th, but check in your area. Starting half-annual seeds indoors is exactly the same as starting hardy annual seeds. (see my blog on hardy annuals here). Make sure they get plenty of light, either from a grow light set up or in a sunny window.


Potting-on Tomatoes

If you started your tomato seeds several weeks ago, and they have at least two “true” leaves, it’s time to pot them on. Choose a 3 ½” to 4” pot. Fill with good, rich, organic potting soil. Plant as deeply as you can in the pot, up to the top leaves, if possible. Tomatoes are vines, so they will root along the stem, providing a much healthier and stable plant in the long run. Water well and place back under lights or in a very sunny window.

To keep your plants from getting too leggy, move them outside to a sheltered, dappled shade area during any warm days (over 65 degrees) for a few hours to make the plants strong and healthy. Just remember to bring them in at night. Tomatoes do not like to be cold!

Now, let's get busy! If you have questions, put them in the comments below!

~Lee Ann~

Valmont Valley Farm

Where Beautiful Magic is Always in Bloom


If you would like to join in supporting my flower farm and receive beautiful bouquets weekly, please sign up for my Flower CSA! Get all the details here!


I would love to hear your comments on my blog posts. Please leave your comments below.

If you find this information inspirational or helpful, I would love it if you would share it with your friends!

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